Construction of Carbon Frameworks through β-Carbon Elimination Mediated by Transition Metals

New catalytic reactions in which transition-metal cyclobutanolates undergo β-carbon elimination have been developed in our laboratory. Rhodium(I) cyclobutanolate generated by the addition of an arylrhodium(I) species to a cyclobutanone undergoes β-carbon elimination to cause ring opening of the four-membered carbocyclic framework. The synthetic potential of the ring-opening process through β-carbon elimination has been demonstrated by its application to a ring-expansion reaction forming a seven-membered ring. Furthermore, a formal alkyne insertion into the cyclobutanone framework is achieved by combining oxidative cyclization of a cyclobutanone and an alkyne on nickel(0) and β-carbon elimination from the resulting nickel(II) cyclobutanolate.