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Reaction of the (Dichloromethyl)oligosilanes R(Me 3 Si) 2 Si−CHCl 2 (R = Me, Ph, Me 3 Si) with Organolithium Reagents and the Synthesis of Novel Kinetically Stabilized Silenes
Author(s) -
Schmohl Kathleen,
Reinke Helmut,
Oehme Hartmut
Publication year - 2001
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200102)2001:2<481::aid-ejic481>3.0.co;2-6
Subject(s) - chemistry , trimethylsilyl , silanes , silane , medicinal chemistry , reagent , trimethylsilyl cyanide , nucleophilic addition , tris , isomerization , nucleophile , steric effects , silylation , hydrolysis , organic chemistry , catalysis , biochemistry
The dichloromethyloligosilanes R 1 (Me 3 Si) 2 Si−CHCl 2 ( 1a , b ) ( 1a : R 1 = Me; 1b : R 1 = Ph), prepared by treatment of methylbis(trimethylsilyl)silane or phenylbis(trimethylsilyl)silane respectively, with chloroform and potassium tert ‐butoxide, treated with the organolithium reagents R 2 Li (R 2 = Me, Ph) to produce the intermediate organolithium derivatives R 1 R 2 2 Si−CLi(SiMe 3 ) 2 ( 10 ). Hydrolysis of 10 during the aqueous workup afforded the [bis(trimethylsilyl)methyl]silanes R 1 R 2 2 Si−CH(SiMe 3 ) 2 ( 2 ); quenching of the reaction mixture with chlorotrimethylsilane gave the [tris(trimethylsilyl)methyl]silanes R 1 R 2 2 Si−C(SiMe 3 ) 3 ( 11 ). The formation of 10 is discussed as proceeding through a remarkable series of isomerization processes involving the transient silenes R 1 R 2 Si=C(SiMe 3 ) 2 ( 7 ), which in the presence of an effective excess of R 2 Li are immediately trapped to give 10 . By the use of sterically congested organolithium derivatives, the nucleophilic addition of R 2 Li to the Si=C bond of 7 can be prevented and kinetically stabilized silenes obtained. Thus, Ph(2,4,6‐ i Pr 3 C 6 H 2 )Si=C(SiMe 3 ) 2 ( 8b ) was synthesized by the reaction of 1b with 2,4,6‐triisopropylphenyllithium (molar ratio 1:2). Similarly, (Me 3 Si)(2,4,6‐ i Pr 3 C 6 H 2 )Si=C(SiMe 3 ) 2 ( 8c ) and (Me 3 Si)(2‐ t Bu‐4,5,6‐Me 3 C 6 H)Si=C(SiMe 3 ) 2 ( 9c ) were prepared from (dichloromethyl)tris(trimethylsilyl)silane ( 1c ) and 2,4,6‐triisopropylphenyllithium or 1c and 2‐ tert ‐butyl‐4,5,6‐trimethylphenyllithium (1:2), respectively, but due to difficulties in the separation of starting material and side products, 8b , 8c , and 9c were obtained in impure form only. Despite the steric congestion, the compounds are reactive and exhibit the usual behavior of silenes. Thus 8b , 8c , and 9c were chemically characterized by the reaction with water to give silanols, by the addition of methanol to give methoxysilanes and by formal [2+2] cycloadditions with benzaldehyde to afford stable 1,2‐oxasiletanes. 1‐Methyl‐1‐(2,4,6‐triisopropylphenyl)‐2,2‐bis(trimethylsilyl)silene ( 8a ), produced as intermediate from 1a and 2,4,6‐triisopropylphenyllithium (1:2), proved to be unstable in the presence of excess aryllithium compound. Thus, only the addition product Me(2,4,6‐ i Pr 3 C 6 H 2 ) 2 SiCH(SiMe 3 ) 2 ( 14 ) was isolated (after hydrolysis).