Palladium catalyzed intramolecular [3 + 2] cycloadditions of diastereomerically pure methylenecyclopropanes MCPs have been investigated. The reaction was found to be stereospecific and occurred with retention of configuration at the carbon center undergoing reaction. A variety of substitution patterns were tolerated on and around the MCP. Deuterium labeling studies have been conducted, and information about the rate of the reaction was obtained. A mechanism has been proposed involving π-allyl intermediates. Pd 2 (dba) 3 /P(OiPr) 3 was a suitable catalyst for most cycloadditions, but molecular sieves or Pd(PPh 3 ) 4 improved the reaction with some substrates. 1,4-Addition of hydride or a carbanion to the enoate was achieved with high selectivity at the newly formed stereocenter. The allylic alcohol was selectively epoxidized with VO(acac) 2 / t -BuOOH.
No takes yet. Share an insight, caveat, or question.
Lautens et al. (1996) studied this question.