Alkenyl dimethylsilanes

Rearrangement of 1-alkenylsilanesf Alkenyl(chloromethyl)dimethylsilanes, readily available from hydrosilylation of alkynes with (chloromethyl)dimethylsilane, rearrange in the presence of aluminum chloride to allyl- and/or cyclopropylsilanes. (Z)-l-Alken-ylsilanes rearrange exclusively to (Z)-allylsilanes (equation I). (E)-l-Alkenylsilanes rearrange to (E)-allylsilanes as the major product (equation II). Cyclopropylsilanes are formed... 

Various types of aryl and alkenyl halides can undergo cross-coupling with 1- w.oro(dimethyl)silyl-l-alkenes. Representative examples are shown by the synthesis of conjugate dienes. For example, ( -l-octenyl(fluoro)dimethylsilane reacted with (E)- or (Z)-iodoalkene by use of (j -CjHsPdCljj (2.5 mol%) catalyst and TASF (1.5 mol) in THF at 50 °C to give the corresponding E,E)- or ( ,Z)-dienes with complete retention of configuration [Eq.(9)j. 

Method A and C have been used for intramolecular cyclopropanation reactions. Thus, 2-silabicyclo[3.1.0]hexanes 5b,c and 2-silabicyclo[4.1.0]heptane 5d have been prepared in moderate yields by treatment of alkenyl(chloromethyl)dimethylsilanes 4b-d with sodium. In the case of 4d, C-H insertion of the intermediate carbene competes with cyclopropanation, and for 4e, it becomes the sole carbene reaction. The corresponding allylsilane 4a does not undergo intramolecular cyclopropanation, and in the case of vinylsilane 6, intramolecular cyclopropanation is probably involved in the formation of silylcyclopropane 7. 

Coupling reactions. Scopes of many well-established reactions continue to be explored. The Heck reaction of alkenyl(2-pyridyl)dimethylsilanes is benefited by the direction of the heteroaromatic group during carbopalladation and the expediency in product purification and catalyst recovery. ... 

Fig. 11. 99.6 MHz Si H] NMR spectrum of the alkenyl(alkyn-l-yl)dimethylsilane in CsDe showing satellites for different types of carbon atoms. The satellites are associated with isotope-induced chemical shifts A C( Si) (-l-l.Oppb for SiMe, —5.0ppb for Si-C =, and -13.1-ppb for Si-C= nuclei), which differ in a systematic way with n and the nature of the carbon atom (see also Scheme 15). Adapted from ref. 108.

Scheme 3-175. Cross-coupling of alkenyl[2-(hydroxymethyl)phenyl]dimethylsilanes with aryl iodides.

Cross-Coupling Reaction of Alkenyl(2-thienyl)dimethylsilanes A General Procedur ... 

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