Abstract
The ambiphilic character of onium ylides enables the intermolecular C-C bond formations, e.g., Wittig- and Corey-reacton. However, ethereal oxonium ylides have been the exception for long. This is due to their extremely short lifetime that kinetically disfavors the attack by carbon-electrophiles. On this basis, in our present study, the utilization of oxonium ylides for synthetically useful carbon-carbon bond forming reaction was investigated. The ambiphilicity of cyclic oxonium ylides seems to bring about the reaction with carbon electrophiles when appropriate modification is made. Indeed, Rh(2)-catalyzed reaction of diazocarbonyl compounds bearing a cyclic acetal ring, in the presence of Rh-catalyst and titanium compound (Lewis acid), effectively afforded the expected carbon-carbon bonded ring-expansion product(s).
