| Synthesis of Net-Shape Ceramic Matrix Composites from Phase Separated Polymeric Precursors |
01 FEB 96 |
|
| Authors:
John S. Haggerty; Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE
|
 | This program seeks means of fabricating thick cross-section monolithic and composite ceramic components using polymeric ceramic precursors, thereby realizing potential processing and quality advantages. This program's strategy for overcoming longstanding problems is based on developing and maintaining a precisely controlled interconnected pore structure within the reacting part, thus providing a pathway through which gaseous reaction products can escape without damaging the part and into which gaseous reactants can freely penetrate, ... |
|
| Applications of Transition Metal Compounds in the Preparation of Useful Silicon-Containing Ceramics |
20 APR 93 |
11 pages |
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
 | There have been many studies of the reactions of organosilicon compounds with diverse transition metal complexes. The original impetus for this research activity was given by the discoveries that heterogeneous platinum and palladium catalysts and chloroplatinic acid were effective hydrosilylation catalysts. In the year that followed, many other transition metal complexes have been found to catalyze the addition of silicon hydrides to organic multiple bonds. Also, transition metal complexes have ... |
|
| 1,2-Dimethyl-1,2-Disila-Closo-Dodecaborane(12), A Silicon Analog of an Ortho-Carborane: Synthesis; X-Ray Crystal Structure; NMR, Vibrational and Photoelectron Spectra; Bonding |
20 APR 93 |
42 pages |
| Authors:
Dietmar Seyferth; Klaus D. Buechner; William S. Rees Jr.; Lars Wesemann; William M. Davis; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The reaction of (CH3)2Si(NMe2)2 with BlOH14 Yields a polymer, BlOH12. Me2NSi(CH3)2NMe2n, whose pyrolysis in a stream of ammonia gives hexagonal boron nitride containing 'a' little silicon nitride. In contrast, CH3(H)Si(NMe2)2 reacts with BlOH14 to give 1,2-dimethyl-1,2-disila-closo-dodecaborane(12) (DMSB) , an air-sensitive solid, the structure of whose 1:1 benzene solvate was determined by X-ray diffraction. This compound crystallizes in the space group P ccn ( 56) with a 10.081(1) b = 10 ... |
|
| Organosilicon Compounds and Polymers and Silicon Ceramics |
23 NOV 92 |
15 pages |
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| A three-year summary of the principal investigator's research on organosilicon chemistry directed toward ceramics synthesis.... Preceramic polymers, Polysilanes, Polycarbosilanes, Silicon carbide. |
|
| Some Useful Bis(trimethylsilylamino)silanes |
02 NOV 92 |
9 pages |
| Authors:
Gerard Mignani; Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| For the preparation of cyclic silametallaazanes of type 1 in particular those in which R is a reactive substituent such as H or CH2=CH, we required the corresponding bis(trimethylsilylamino) silanes. Such compounds, we found, could be prepared readily by a Me3Si-for-H rearrangement reaction first reported by Wannagat and Niederprum in 1961. |
|
| Preceramic Polymers: Past, Present and Future |
02 NOV 92 |
31 pages |
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| A review of preceramic polymer chemistry is given. Preceramic polymers are needed because of high technology applications which arose in our aerospace age. A discussion of the early work in Germany and Japan leads to an enumeration of the requirements that must be met if a polymer is to be a useful precursor in pyrolytic ceramic synthesis. Seven current research directions in preceramic polymer chemistry are discussed and the at ... |
|
| Synthesis and Useful Reactions of Organosilicon Polymeric Precursors for Ceramics |
05 APR 92 |
14 pages |
| Authors:
Dietmar Seyferth; Carsten Strohmann; Henry J. Tracy; Jennifer L. Robison; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| A general discussion of the polymer pyrolysis route to ceramics what it is, why it is important, and the chemical considerations that are important in its implementation - is followed by some recent examples from research at MIT involving polysilazane and polysilane chemistry. Preceramic polymers, Polysilnes, Organosilicon polymers, Silicon nitride, polysilazanes, Silicon carbide. |
|
| Vibrational Spectrum and Structure of 1,2-Dimethyl-1,2-disila-closo- dodecaborane |
05 APR 92 |
12 pages |
| Authors:
S. S. Bukalov; L. A. Leites; Lars Wesemann; Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The IR spectrum (thin film) of 1,2-dimethyl-1,2-disila-closo- dodecacarborane, DMSB, in the region 200 - 3600 cm-1 and its Raman spectrum (solid sample) in the region 5 - 3600 cm-1 are reported. It is concluded that the molecular bonding in DMSB is weaker than that in o-carborane. A Raman band at 399 cm-1 is tentatively assigned to the Si-Si bond. boron compounds, organosilicon compounds, carborane analogs, IR and Raman spectroscopy. ... |
|
| Silicon Ceramics with a Dash of Boron |
10 MAY 91 |
15 pages |
| Authors:
Dietmar Seyferth; Herbert Plenio; William S. Rees Jr.; Klaus Buechner; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| This review deals with the synthesis of cross-linked silazanyl borazine polymers that are excellent precursors for BN/Si3N4 composites, with decaborane-diamine polymers that serve as BN precursors and with the serendipitous discovery of an ortho-carborane. |
|
| Characterization of Hydridomethylpolysilazane: A Precursor to SiC/Si3N4 Ceramics |
91 |
|
| Authors:
Regina M. Stewart; Neal R. Dando; Dietmar Seyferth; Anthony J. Perrotta; ALUMINUM CO OF AMERICA ALCOA CENTER PA ALCOA TECHNICAL CENTER
|
| Development of inorganic and organometallic polymers as preceramic materials for the synthesis of silicon carbide (SiC) and silicon nitride (Si3N4) ceramics is an area of considerable research emphasis in modern materials science. These materials hold tremendous potential for use in fiber drawing, as protective coatings for ceramic reinforcement fibers, for injection molding or casting of complex shapes and as binders for ceramic powder processing. Along with the development of divergent ... |
|
| 1,2-Dimethyl-1,2-Disila-Closo-Dodecaborane(12), the First Silicon Analog of an Ortho-Carborane |
04 MAY 90 |
13 pages |
| Authors:
Dietmar Seyferth; Klaus Buechner; William S. Rees Jr.; William M. Davis; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The icosahedral carboranes, especially those in which the two cluster carbon atoms are vicinal (o-carboranes), have received much attention since the first reports of their existence in 1963. Notably absent in the many publications on this class of boron cluster compounds over the intervening 25 odd years have been examples of icosahedral clusters in which the two monosubstituted carbon atoms of an o-carborane have been replaced by two monosubstituted silicon, ... |
|
| Polymeric Aluminasilazane Precursors for Aluminosilicon Nitride |
04 MAY 90 |
9 pages |
| Authors:
Dietmar Seyferth; Gregor Brodt; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The reaction of trimethylaluminum with the cyclic oligomers obtained by ammonolysis of methyldichlorosilane results in evolution of methane and formation of soluble, cross-linked aluminasilazanes. Pyrolysis of the products in a stream of argon gives a good yield of black aluminosilicon carbonitride, while pyrolysis in a stream of ammonia results in formation of white aluminosilicon nitride. Keywords: Silicon nitride, Aluminum nitride, Silicon carbonitride, Preceramic polymers, Organosilicon compounds, Organoaluminum compounds, Polysilazanes, Magneto-optical ... |
|
| Borasilazane Polymeric Precursors for Borosilicon Nitride |
90 |
|
| Authors:
Dietmar Seyferth; Herbert Plenio; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The reaction of H3B-S(CH3)2 with the (CH3SiHNH)n cyclic oligomers obtained by ammonolysis of methyldichlorosilane (CH3SiHCl2) results in evolution of hydrogen and formation of cross-linked products that contain borazine rings as well as boron atoms that are linked to three nitrogen atoms. Pyrolysis of the products in a stream of argon gives a high yield of a black "borosilicon carbonitride," whereas pyrolysis in a stream of ammonia gives white "borosilicon nitride" ... |
|
| A New Procedure for "Up-Grading" the Nicalon Polycarbosilane and Related Si-H Containing Organosilicon Polymers |
90 |
|
| Authors:
Dietmar Seyferth; Christine A. Sobon; Jutta Borm; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
|
| Birth, Death and Transfiguration; The Synthesis of Preceramic Polymers, Their Pyrolysis and Their Conversion to Ceramics |
31 MAY 89 |
43 pages |
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| An introduction to preceramic polymer chemistry. Applications of preceramic polymers; chemical considerations important in their design and synthesis. Examples from known silicon-containing preceramic polymers. Inorganic and organometallic polymers are those macromolecular systems in which the polymer backbone contains elements other than the carbon, oxygen and nitrogen usually found in organic polymers. |
|
| Non-Polymeric Binders for Ceramic Powders: Utilization of Neutral and Ionic Species Derived from Decaborane(14) |
13 MAY 89 |
19 pages |
| Authors:
William S. Rees Jr.; Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The pyrolytic conversion of bis-Lewis base adducts of decaborane(14), L.B sub 10 H sub 12.L (L= neutral monophosphine) and phosphonium salts of the (B sub 10 H sug 10)2- anion (e.g., (Ph sub 4 P sub (+)2, etc.), to ceramic materials has been studied. All species examined served as binders for a variety of non-oxide refractory ceramic powders (e.g., B sub 4 C, BN, BP, B sub 13 P sub ... |
|
| Stoichiometric and Catalytic Ring Opening of Hexaalkylcyclodisilazanes by Organoalkali Reagents |
13 MAY 89 |
43 pages |
| Authors:
Dietmar Seyferth; Joanne M. Schwark; Regina M. Stewart; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The action of organoalkali reagents (RLi, RLi/Me3CONa, RLi/Me3COK) on cyclo-(Me2SiNMe)2 and cyclo-(Me2SiNPri)2 results in ring opening to give alkali metal amides of the type RMe2SiNMeSiMe2NMeM (M= Li, Na, K) which react with chlorosilanes, R'Me2SiC1, to give the expected linear trisilazanes. Relatively unhindered lithium amides also open the cyclo-(Me2SiNMe)2 ring. The use of a catalytic amount of RLi or RLi/Me3CONa (but not of RLi/Me3COK) results in ring opening polymerization of cyclo-(Me2SiNMe)2 ... |
|
| Organosilicon Compounds and Polymers and Silicon Ceramics |
02 MAR 89 |
14 pages |
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The n-BuLi/Me3COK reagent metalates every fourth CH2 group of (CH3) 2SiCH2. The metalated polymer was converted to vinyl-containing polycarbosilanes whose reaction with (CH3SiH)x(CH3Si)yn gave useful preceramic polymers. Cross- linkable CH3(H)SiCH2N has been prepared using CH3(Ph)SiCH2n as starting material. The reactions of (CH3SiH)x(CH3Si)yn with Cp2MMe2 (M= Ti, Sr, Hf) gave precursors for SiC/MC blends. 1,1,3,3-Tetramethyl-1,3-disilacyclobutane can be metalated with t-Buli/TMEDA. Keywords: Metal carbonyls, 1,1,3,3-Tetramethyl-1,3- disila cyclobutane, Biscyclopentad ienyldimethyl derivatives, Polycarbosilanes, Polysilanes, ... |
|
| Phosphorus-Containing Derivatives of Decaboranes(14) as Precursors of Boron-Containing Materials |
25 JUN 88 |
27 pages |
| Authors:
William S. Rees Jr; Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| Ceramic materials whose properties are attractive for high technology applications often fail to realize their full potential of usefulness due to an inability to be fabricated into complex, durable shapes. One such class of materials is that of the boron-containing ceramics, e.g., boron carbide, boron nitride, boron phosphides, aluminum boride, and boron silicides. We now report the results of an effort to extend the use of preceramic polymers to boron- ... |
|
| The Preparation of Silicon-Containing Ceramics by Organosilicon Polymer Pyrolysis |
25 JUN 88 |
37 pages |
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| Silicon-containing ceramics include the oxide materials, silica and silicates; the binary compounds of silicon with non-metals, principally silicon carbide and silicon nitride; silicon oxynitride and the sialons; main group and transition metal silicides, and, finally, elemental silicon itself. There is a vigorous research activity throughout the world on the preparation of all of these classes of solid silicon compounds by the newer preparative techniques. Silicon carbide SiC and silicon nitride ... |
|
| High Yield Synthesis of B4C/BN Ceramic Materials by Pyrolysis of Polymeric Lewis Base Adducts of Decaborane(14) |
04 NOV 87 |
|
| Authors:
William S. Rees Jr.; Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| In previous work, we have developed useful polymeric precursors whose pyrolysis provides high yields of silicon nitride or silicon nitride/silicon carbide blends. The main applications of such preceramic polymers (preparation of ceramic fibers and coatings and their use as binders for ceramic powders) require that the polymeric precursor be processable, i.e., soluble in organic solvents and or fusible. Although the major efforts of workers in the preceramic polymer area have, ... |
|
| The Preparation of Titanium Nitride and Titanium Carbonitride by the Preceramic Polymer Route |
04 NOV 87 |
|
| Authors:
Dietmar Seyferth; Gerard Mignani; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The pyrolysis of selected titanium amides in a stream of ammonia gives titanium nitride. In a stream of argon titanium carbonitride is produced. We have developed useful routes for the preparation of silicon and boron carbonitrides and nitrides by the pyrolysis of suitable polymeric precursors, and we were interested in developing such an approach for the synthesis of titanium carbonitride and nitride. Keywords: Titanium nitride, Titanium carbonitride, Titanium amides, Ceramics. ... |
|
| Organosilicon Polymers as Precursors for Silicon Containing Ceramics: Recent Developments |
14 AUG 87 |
|
| Authors:
Dietmar Seyferth; Gary H. Wiseman; Yuan-Fu Yu; Joanne M. Schwark; Charles A. Poutasse; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| A review of the dehydrocyclodimerization route to preceramic polysilazanes starting from (CH3SiHNH)n, the ammonolysis product of CH3SiHC12, as well as similar processing of coammonolysis products and the application of the living polymer intermediates involved in this chemistry in the preparation of novel hybrid preceramic polymers. Keywords: Silicon nitride, Polysilazanes, Silicon carbide, Ceramics. |
|
| Applications of Methyldichlorosilane in the Preparation of Silicon- Containing Ceramics |
14 AUG 87 |
|
| Authors:
Dietmar Seyferth; Gary H. Wiseman; Yuan-Fu Yu; Tom S. Targos; Christine A. Sobon; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| Methyldichlorosilane is a useful starting material in the preparation of silicon-containing ceramics. Its hydrolysis, aminolysis and sodium condensation give products whose further polymerization or cross-linking yields useful perceramic polymers. Keywords: Silicon nitride, Polysilanzanes, Silicon carbide, Ceramics, Polysilanes, Metal alkoxides. |
|
| Polycarbosilanes - An Overview |
14 AUG 1987 |
33 pages |
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| Polycarbosilanes, in their broadest definition, are organosilicon polymers whose backbone is composed of silicon atoms, appropriately substituted, and difunctional organic groups which bridge the silicon atoms. The polycarbosilanes may be linear, or they can be cyclic or polycyclic. A review of polycarbosilanes with emphasis on polysilmethylenes is presented. Also covered are the Yajima and Bayer AG polycarbosilane precursors for Silicon Carbide. |
|
| Organosilicon Polymers as Precursors for Silicon-Containing Ceramics |
23 FEB 87 |
|
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| Following general comments about the preceramic polymer approach to the preparation of ceramic materials, we describe the preparation of a novel polysilazane by dehydro-cyclodimerization of the ammonolysis product of Methylsilicon Hydrochloride , the conversion of such polymers to ceramic products and their use in upgrading polysilanes of type (CH3SiH)x(CH3Si)yn) and (CH3Si(H)CH2)n to more useful ceramic precursors. |
|
| The Preceramic Polymer Route to Silicon-Containing Ceramics |
23 FEB 87 |
|
| Authors:
Dietmar Seyferth; Yuan-Fu Yu; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| Silicon-containing ceramics include the oxide materials, silica and the silicates; the binary compounds of silicon with non-metals, principally silicon carbide and silicon nitride, silicon oxynitride and the sialons; main group and transition metal silicides, and, finally, elemental silicon itself. While there is vigorous research activity throughout the world on the preparation of all of these classes of solid silicon compounds by the newer preparative techniques, in this report we will ... |
|
| Organosilicon Compounds and Organosilicon Polymer Intermediates |
09 DEC 85 |
|
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| a. The sodium condensation of CH3SiHCl2 has been studied. It gives products of type (CH3SiH)x(CH3Si)y)n which are not useful precursors for SiC. b. Base-catalyzed reorganization of the polysilanes in (a) gives new materials whose pyrolysis gives markedly higher ceramic yields. c. Useful preceramic hybrid polymers are obtained by the reaction of the polysilanes in (a) with a poly (silylamide) of type ((CH3SiHNH)a(CH3SiN)b-(CH3SiHNK)c)m. d. This hybrid polymer approach also is useful ... |
|
| Gem-Difluoroallyllithium: Preparation by Lithium-Halogen Exchange and Utilization in Organosilicon and Organic Synthesis |
23 MAR 1983 |
|
| Authors:
Dietmar Seyferth; Robert M. Simon; Dennis J. Sepelak; Helmut A. Klein; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| gem-Difluoroallyllithium may be generated by lithiumbromine exchange between n-butyllithium and CH2=CHCF2Br at -95 degrees C using an in situ procedure. When this Li(CF2CHCH2) preparation is carried out in the presence of chlorosilanes, aldehydes, ketones and esters, products of type R3SiCF2CH=CH2, RCH(OH)CF2CH=CH2, RR'C-(OH)CF2CH=CH, respectively, are formed, often in good yield. The factors determining the regioselectivity in additions to C=0 of unsymmetrically substituted allylic lithium reagents are discussed. (Author) |
|
| Organosilicon Compounds and Organosilicon Polymer Intermediates |
21 MAR 1983 |
12 pages |
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| Studies of the highly reactive Si-C bonds of hexamethylsilacyclopropane and 1,1-dimethy1-3,4-bis(trimethylsilyl)- silacyclopropene and of the reactive Si-Si bond of octamethyl1-1,2- disilacyclobutane completed. RP- and RAs-bridged ferrocenophanes were prepared and their reactions with organolithium reagents studied. Ferrocenylenephenylphosphine polymers were prepared for use as ligands in catalysis studies. Their cobalt complexes are active hydroformylation catalysts. A novel and useful route to acylsilanes based on the carbon monoxide-derived acyllithium reagents has been developed. ... |
|
| A Novel Liquid Silazane Precursor to Silicon Nitride |
28 OCT 1982 |
|
| Authors:
Dietmar Seyferth; Gary H. Wiseman; Christian Prud'homme; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The reaction of dichlorosilane, H2SiCl2, with gaseous ammonia in dichloromethane or diethyl ether solution results in formation of a silazane oil containing silicon, hydrogen, and nitrogen in good yield. This ammonolysis product can be pyrolyzed in a nitrogen atmosphere (temperature to 1150 C) to give alpha-Si3N4 in about 70% yield. The ceramic product formed has a relatively porous, fine-grained microstructure with some cracks and blisters. |
|
| The Synthesis of 3,3-Difluoroallyl Derivatives of Silicon by an Organophosphorus Route. |
06 AUG 1980 |
|
| Authors:
Dietmar Seyferth; Karl R. Wursthorn; Thomas F. O. Lim; Dennis J. Sepelak; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| 3,3-Difluoroallylderivatives of silicon have been prepared by the reaction of difluorochloromethane with ylides of type Ph3P=CHCH2SiR3 (SiR3 = SiMe3, SiMe2H, SiMe2OSiMe3, SiMe(OSiMe3). Also prepared by this procedure was Me3SiCH2C-2 (CH3)=CF2, but Me3SiCH2c(C6H5)=CF2 could not be prepared in this way, probably because the ylide, Ph3P=C(C6H5) CH2SiMe3 was not sufficiently basic to deprotonate HCF2C1. The thermal stability of Me3SiCH2CH=CF2 was assessed and a few of its reactions examined: additon of CCl2 and ... |
|
| Gem-Difluoroallithium: Improved Synthesis Brings Improved Applicability. |
15 APR 1980 |
|
| Authors:
Dietmar Seyferth; Robert M. Simon; Dennis J. Sepelak; Helmut A. Klein; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The action of N-butyllithium in hexane on CF2BrCH=CH2/CF2=CH-CH2Br (5:2 yield 20:1 mixture) in 5:1:1 THF/Et2O/pentane at -95 degrees C generates gem-difluoroallyllithium which may be trapped, generally in good yield, by the in situ procedure using triorganochlorosilanes (yield R3SiCF2CH=CH2) and aldehydes and ketones (yield RR'C(OH)CF2-CH=CH2). (Author) |
|
| New Functional Allylic Lithium Reagents: Gem-Dialkoxyallyllithium Reagents: A Useful Route to BETA-Silyl and beta-Stannylpropionate Esters. |
08 FEB 1980 |
|
| Authors:
Dietmar Seyferth; Robert E. Mammarella; Helmut A. Klein; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The reaction of sec-butyllithium with acrolein dialkyl acetals in THF or in THF/Et2O/pentane at -95 C results in formation of gem-dialkoxyallyllithium reagents, Li(CH2CHC(OR)2). These react with organosilicon and organotin chlorides to give ketene acetals, R3SiCH2CH=C(OR)2 and R3SnCH2CH=C(OR)2. The acid hydrolysis of these products produces beta-substituted proprionic acid esters, R3SiCH2CH2CO2R and R3SnCH2CH2CO2R. Reactions of these lithium reagents with allyl bromide gave esters of 5-hexenoic acid, CH2=CH(CH2)3CO2R (R = Me, Et). (Author) ... |
|
| Gem-Difluoroallyllithium: Preparation by the Transmetalation Procedure and some Reactions. |
28 JUN 1979 |
|
| Authors:
Dietmar Seyferth; Karl R. Wursthorn; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| 3,3-Difluoroallyltrimethyltin has been prepared by the reaction of beta-trimethylstannylethylidenetriphenylphosphorane with chlorodifluoromethane. This tin compound reacts with n-butyllithium in tetrahydrofuran at -95 C to generate gem-difluoroallyllithium. The latter, however, is not stable in solution at that temperature. If generated in situ in the presence of a triorganochlorosilane, products of type R3SiCF2CH-CH2 are obtained in good yield. Addition to the C=O bond of 3-pentanone to give (C2H5)2C(OH)CF2CH=CH2 was achieved by the method ... |
|
| Wittig Synthesis of Allylic Organosilicon Compounds. |
01 JUN 1979 |
|
| Authors:
Dietmar Seyferth; Karl R. Wursthorn; Thomas F. O. Lim; Dennis J. Sepelak; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The reactions of Beta-silylalkylidenetriphenylphosphoranes, prepared by the action of alkylidenetriphenylphosphoranes on iodomethyl-silicon compounds, followed by deprotonation of the resulting Beta-silylalkyltriphenylphosphonium iodides, with aldehydes and ketones provide a useful route to allylic silicon compounds. |
|
| The Preparation of Substituted Allyllithium Reagents from Allyltin Compounds by Transmetalation. |
10 APR 1979 |
|
| Authors:
Dietmar Seyferth; Robert E. Mammarella; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The reaction of substituted allyltrimethyltin compounds with methyllithium in tetrahydrofuran gave substituted allyllithium reagents. Reactions of the latter with trimethylchlorosilane, iodomethane (or benzyl bromide) and carbonyl compounds were examined. (Author) |
|
| New Functional Allylic Lithium Reagents: Gem-Dialkoxyallyllithium Reagents: A Useful Route to beta-Silyl and b-Stannylpropionate Esters, |
1979 |
|
| Authors:
Dietmar Seyferth; Robert E. Mammarella; Helmut A. Klein; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The reaction of sec-butyllithium with acrolein dialkyl acetals in THF or in THF/Et2O/pentane at -95 C results in formation of gem-dialkoxyallyllithium reagents, Li(CH2CHC(OR))2. |
|
| Organosilicon Compounds and Organosilicon Polymer Intermediates. |
21 NOV 1978 |
|
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| A summary of three years of research directed mainly at a development of the chemistry of silacyclopropanes and silacyclopropenes. (Author) |
|
| Gem-Chloro(Trimethylsilyl)Allyllithium: A Novel Ambient Nucleophile. |
27 MAR 1978 |
|
| Authors:
Dietmar Seyferth; Robert E. Mammarella; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| Gem-Chloro(Trimethylsilyl)allyllithium, Li(Me3SiCClCHCH2), was prepared by the transmetalation reaction between Ph3PbCH2CH double bond C(Cl)SiMe3 and n-butyllithium in THF at -90 C. The terminus at which new bond formation occurs in reactions of this ambident nucleophile appears to be determined by electronic and steric factors. |
|
| The Reaction of 3,3-Dichloroallyltrimethylsilane with N-Butyllithium. |
27 MAR 1978 |
|
| Authors:
Dietmar Seyferth; Robert E. Mammarella; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| In a recent investigation, the novel ambident allylic lithium reagent gem-chloro(trimethylsilyl)allyllithium, was prepared and its reactions with a variety of substrates was studied. (Author) |
|
| The Generation of gem-Difluoroallyllithium by the Transmetalation Reaction. |
28 JUL 1977 |
|
| Authors:
Dietmar Seyferth; Karl R. Wursthorn; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| 3-3-Difluoroallyltrimethyltin was prepared by reaction of chlorodifluoromethane with the ylide reagent Ph3P=CHCH2SnMe3, WUNR053618. gem-Difluoroallyllithium, which was generated by the reaction of n-butyllithium with 3-3-difluoroallyltrimethyltin in THF at -95, was of very limited stability at that temperature. However, in situ procedures and alternate incremental addition procedures allowed its application in the synthesis of 1-1-difluoroallylsilanes from chlorosilanes and of CH2-CHCF2C(OH)Et2 from 3-pentanone. (Author) |
|
| A General Route to Terminally Substituted Allylic Derivatives of Silicon and Tin. Preparation of Allylic Lithium Reagents. |
01 JUN 1977 |
|
| Authors:
Dietmar Seyferth; Karl R. Wursthorn; Robert E. Mammarella; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| It is obvious that this new route to allylic compounds of silicon and tin should be quite general in its scope of applicability. By appropriate variation of the phosphorus ylide and the carbonyl substrate in these reactions, allylic derivatives of silicon and tin of type Me3MCH2C(R)=CR'R'', where R, R' and R'' should be capable of wide variation, should be accessible. The allyltins thus prepared would provide starting materials for many ... |
|
| Highly Halogenated Organic and Organometallic Materials and Strained Ring Organometallics. |
15 DEC 1975 |
|
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| A brief summary of research results of the period 1 Oct. 1973 - 31 August 1975 on new organometallic (Hg and Pb) Divalent Carbon Transfer Agents, new carbene chemistry, halogenated organomagnesium and -lithium reagents and the first silacyclopropanes. (Author) |
|
| Highly Halogenated Organic and Organometallic Materials. |
19 NOV 1971 |
|
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| Very briefly discussed is research concerning the generation of divalent carbon intermediates through alpha-elimination reactions from organometallic precursors. Such reagent systems are of great value since they allow the generation and transfer to substrate of carbenes under very mild conditions in the virtual absence of complicating side reactions. This has allowed us to study in some detail the chemistry of carbenes and, in particular, to carry out carbene reactions which ... |
|
| Organometallic Synthesis of Reactive Intermediates. |
01 OCT 1970 |
|
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The report summarizes research involving the generation of divalent carbon intermediate through alpha-elimination from organometallic precursors. The compounds formed are the result of addition of dihalocarbenes across double bonds and insertion reactions into carbon-hydrogen, tin-tin, tin-halogen, silicon-carbon, silicon-mercury, and carbon-mercury bonds. (Author) |
|
| STUDIES ON THE CHEMISTRY OF GROUP III AND V ELEMENTS. |
30 SEP 1969 |
|
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| The research had the stated objectives (1) to develop new organometallic carbene precursors and new carbene chemistry, and (2) to study new reactions found with regard to scope and mechanism. Results and conclusions are very briefly summarized and a listing of publications, lectures, and scientific personnel associated with the project is provided. (Author) |
|
| ORGANOMETALLIC SYNTHESIS OF REACTIVE INTERMEDIATES. |
04 JAN 1968 |
|
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| A summary is given of a program of research involving the generation of divalent carbon intermediates through alpha-elimination from organometallic precursors. Particular attention was given to the chemistry of carbenes and of phenyl(trihalomethyl) mercury reagents. A list of the 22 papers published in conjunction with this work is included. |
|
| STUDIES IN ORGANOPHOSPHOROUS AND ORGANOMERCURY CHEMISTRY. |
30 SEP 1966 |
|
| Authors:
Dietmar Seyferth; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| A very brief review is given of work which involved (1) the reactions of organolithium reagents with quarternary phosphonium halides; (2) syntheses based on phosphine alkylidene chemistry; and (3) generation of carbenes by the thermolysis of PhHgCX3. A list of the 31 papers published as a result of the work is included. |
|
| HALOMETHYL-METAL COMPOUNDS. I. PREPARATION OF PHENYL (TRIHALOMETHYL) MERCURY COMPOUNDS, |
02 FEB 1965 |
|
| Authors:
Dietmar Seyferth; James M. Burlitch; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
|
| Detailed procedures for the preparation of C6H5HgCCl3, C6H5HgCCl2Br, C6H5HgCClBr2 and C6H5HgCBr3 by the Reutov-Lovtsova method are given. Evidence is presented which indicates that the reaction of phenylmercuric halide, haloform and potassium tert-butoxide forms C6H5HgCX3 by way of nucleophilic displacement of halide ions from mercury by the trihalomethyl anion. (Author) |
|
Reports by Author
