886.
3-Methyl-1-tris(trimethylsilyl)silyl-2-butenol(1) ( 6 ) and (E)-3-Phenyl-1-tris(trimethylsilyl)silyl-2-propenol(1) ( 7 ) were prepared by the reaction of tris(trimethylsilyl)silyllithium ( 5 ) with 3,3-dimethylacrolein and (E)-cinnamaldehyde, resp. The alcohols 6 and 7 proved to be suitable precursors for the generation of the transient 1-silabutadienes (Me
3Si)
2Si = CHCH = CR
1R
2 8 and 9 ( 8 : R
1 = R
2 = Me; 9 : R
1 = H, R
2 = Ph) following the principle of the modified Peterson reaction. Thus, 6 and 7 after deprotonation with excess MeLi in ether at low temperatures eliminated trimethylsilanolate and gave 8 and 9 , which were trapped by the excess organolithium reagent undergoing nucleophilic 1,2- or 1,4-addition reactions. In the absence of scavengers, e.g. when 8 and 9 were generated by treatment of 6 and 7 with stoichiometric quantities of MeLi in ether, the 1-silabutadienes dimerize in a [2 + 2] head-to-head fashion to give the 1,2-disilacyclobutanes 17 and 18 , resp., besides polymeric material. Treatment of the alcohol 6 with MeLi in tetrahydrofuran caused a 1,3-Si,O-trimethylsilyl shift affording the alkoxysilane (Me
3Si)
2SiH? CH(OSiMe
3)CH = CMe
2 19 .
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