PHENYLDIMETHYLSILYL-SUBSTITUTED KETENES AND BISKETENES

The phenyldimethylsilyl-substituted monoketene PhMe(2)SiCH=C=O (1) and bisketene (PhMe(2)SiC=C=O)(2) (3) have been prepared and compared to the corresponding Me(3)Si- and t-BuMe(2)Si-substituted species. The C- 13, O-17, and Si-29 NMR spectra fit the pattern shown by other silylke tenes and provide no evidence for transmission of a substituent effect of the Ph group through the silicon to the ketenyl group, as has been proposed for PhMe(2)Si-substituted radicals. The UV spectrum of 1 doe s show a longer lambda and greater epsilon than for t-BuMe(2)SiCH=C=O, and this may indicate some interaction of the phenyl group with the k etene chromophore, while the greater reactivity of 1 in hydration comp ared to t-BuMe(2)SiCH=C=O is ascribed to the inductive effect of the p henyl. The very similar ring-opening reactivity of the bis(phenyldimet hylsilyl)cyclobutenedione (6) to form 3 compared to the bis(Me(3)Si) a nalogues also provides no evidence of a significant interaction of the phenyl with the ketene. A new type of stabilized 1,8-bisketene based on the arylbis(dimethylsilyl) grouping, namely, 1,4-bis(ketenyldimethy lsilyl)benzene (12), has been prepared for the first time.