Journal of the American Chemical Society, Vol.134, No.5, 2766-2774, 2012
Asymmetric Synthesis of Dihydroindanes by Convergent Alkoxide-Directed Metallacycle-Mediated Bond Formation
A convergent synthesis of highly substituted and stereodefined dihydroindanes is described from alkoxide-directed Ti-mediated cross-coupling of internal alkynes with substituted 4-hydroxy-1,6-enynes (substrates that derive from 2-directional functionalization of readily available epoxy alcohol derivatives). In addition to describing a new and highly stereoselective approach to bimolecular [2 + 2 + 2] annulation that delivers products not available with other methods in this area of chemical reactivity, evidence is provided to support annulation by way of regioselective alkyne alkyne coupling followed by metal-centered [4 + 2] rather than stepwise alkene insertion and reductive elimination. Overall, the reaction proceeds with exquisite stereochemical control and defines a convenient, convergent, and enantiospecific entry to fused carbocycles of great potential value in target-oriented synthesis and medicinal chemistry.