Abstract
Dichloroneopentylsilene, Cl2Si=CHCH2Bu' (1), is produced from vinyltrichlorosilane (2) and LiBu' in n-pentane at —78 °C. The reactions of 1 with aromatic aldehydes like benzaldehyde and the 4-methoxy- or 4-fluoro-substituted derivatives, naphthalene-1- and -2- and 9-anthracenecarbaldehyde, furfurale and its S-analogous thiophene carbaldehyde yield 1,2-silaoxetanes by [2+2] cycloaddition with the carbonyl group. The same is true for the reactions of 1 with pivaline-, butyr- and acetaldehyde. The silaoxetanes cannot be isolated; the formation of dichlorovinylsiloxanes and the olefinic compounds R—CH=CH —CH2Bu′suggests that the cycloreversion of the Si—O four-membered ring competes with an intramolecular isomerization, evidently via formation of a zwitterionic intermediate . The product formation by coupling reactions of lithiated aldehydes and 2 is excluded by performing analogous reactions with the chlorosilanes Me2SiCl(R) (R = Cl, Me, Vi).

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