Synthesis and structural analysis of nine-membered enyne nitrogen heterocycles

Abstract

An efficient approach to the nine-membered enyne nitrogen heterocycle 3 is presented. 1H NMR analysis reveals that both 3a (R = H, X = Ts) and 3b (R = Me, X = Ts) exhibit significant labile planar chirality in solution at ambient temperature. The X-ray analysis of 3b shows that the enantiotopic faces of the alkene are differentiated by the alkyne moiety in the solid state.