Asymmetric Cyclization-Hydroboration of 1,6-Enynes

Significance

This Rh(I)-catalyzed asymmetric cyclization-hydroboration of 1,6-enynes provides an expedient route to functionalized carbocycles and heterocycles. The sequence can be terminated either via Pd-catalyzed arylation or by oxidation to access the corresponding ketone. 1,7-Enynes and 1,6-enynes that possess either a terminal alkyne or a substituted alkene bond did not undergo the desired cyclization. This is a complementary variation of a Rh-catalyzed cyclization-arylation of enynes with arylboronic acids reported by T. Miura et al. J. Am. Chem. Soc. 2005, 127, 1094-1095. The use of catecholborane as the borylating agent in the present method allows for subsequent transformation of the boronic ester intermediate.