Sulphonation allylsilanes

As reactions 68 and 69 above exemplify, the substitution of the allylsilane usually takes place with an allylic shift (Se2 ). This can be synthetically useful, for example in the isomerization of allyl sulphones 123 to vinyl sulphones 124 (equation 74)145. The reaction is also highly stereospecific (>90% E) (vide infra). 

Allylsilanes result from allyl sulphides which have siloxy subsdtuents with regio and stereochemically using allyl-lithium, from alkenyl Fischer carbene complexes with silanes through addition of Si-H to the carbene, and opdcally active y-silylallylamines result frnn a n-allylPd intermediate obtained from the carbonate using amines or azide, while allyldichlorosilane can be prepared by the direct method at 220 - 320 C as the main product. The protodesilyladon of allylsilanes provides a route to vinyl sulphones while silylmethyl allyl sulphones result from silylmethyl cuprates and sulphonylalka-1,2-dienes, and are used in the... 

The perfluorinated resiri sulphonic acid trimethylsilyl ester (66 Nafion-TMS ) has been developed as a new silylating agent for alcohols, phenols, etc7 The substrate and resin are shaken in dichloromethane at room temperature, with triethylamine if necessary, before the resin is simply removed by filtration from the solution of products. The trimethylsilylation of tertiary alcohols with trimethylsilyl chloride-triethylamine has been found to be catalysed by various additives, including DMSO and HMPT. Allylsilanes have been used as new silylating reagents for alcohols in the presence of an acid catalyst [equation (19)] trimethylsilyl and t-butyldimethylsilyl (TBDMS) ethers can be made in this way. 

Silicon.— Allylsilanes are outstandingly useful carbon nucleophiles as a result of their ability to react with electrophiles in a controlled and specific manner to form new carbon-carbon bonds. Furthermore, metallation to give a-(trimethyl-silyl)allylic carbanions introduces the possibility of an additional level of control over the mode of attack (either a or y) exhibited by the allylsilane. It is not surprising, therefore, to find the chemistry of these species occupying a prominent position in this year s organosilicon literature, and in addition to the many applications reported some new routes to these compounds have been described. One such example is shown in Scheme 13, in which the starting silyl sulphone is readily prepared by oxidation of the product obtained from reaction of thio-phenol with vinyltrimethylsilane." ... 

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