149167-16-8Relevant academic research and scientific papers
(Phenylsulfonyl)allenes as substrates for cycloaddition reactions: Intramolecular cyclizations onto unactivated alkenes
Padwa, Albert,Meske, Michael,Murphree, S. Shaun,Watterson, Scott H.,Ni, Zhijie
, p. 7071 - 7080 (2007/10/02)
The reaction of a series of allyl-substituted bis(phenylsulfonyl)methanes or dimethyl malonates with 2,3-bis(phenylsulfonyl)-1,3-butadiene in the presence of base afforded alkenyl-substituted allenes in good yield. The reaction proceeds by initial attack of the soft carbanion onto the terminal position of the diene, and this is followed by PhSO2- elimination to give the phenylsulfonyl-substituted allene. Themal [2 + 2]-cycloaddition proceeded across the C1-C2 double bond of the allene with completely sterospecificity. Stepwise bonding prefers to occur in a 1,6-exo manner rather than in a 1,7-endo fashion. Substitution at the 7-position of the π-bond causes a crossover in the regioselectivity of the [2 + 2]-cycloaddition process. All products can be rationalized by a mechanism which includes an initial carbon-carbon bond formation involving the central allene carbon to give a diradical intermediate. The product distribution is then determined by the substitution pattern of the alkene and the fate of the diradical intermediate.
