Isobutene ene reactions

Benzenoid disilanes are known to undergo photorearrangement via a silene intermediate. A conversion of this type (Scheme 4) has been proposed to account for the photoreaction of 1,2-bis(pentamethyldisilanyl)benzene (193) with isobutene ene-reaction of the photochemically generated silene (194) with isobutene affords 2-(isobutyldimethylsilyl)-1-(pentamethyldisilanyl) -3-(trimethyIsilyl)benzene (195).1,3-Bis(pentamethyldisilanyl) benzene undergoes an analogous photoreaction with isobutene to give 3-(isobutyldimethylsilyl)-1-(pentamethyldisilanyl) -4- (trimethylsilyl)benzene the silepin (196) is a minor product of this reaction and arises from the silene (197) as shown in Scheme 5. 

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