Synthesis of Chromeno[4,3- <i>d</i> ][1,3]oxazines through Copper(I)-Catalyzed Cycloisomerization of 1,11-Enynes

A copper(I)-catalyzed cycloisomerization of propargyl oxime-derived 1,11-enynes was developed to prepare various chromeno[4,3-<i>d</i>][1,3]oxazines containing two or three stereocenters in good yields with high regioselectivity and diastereoselectivity. Mechanistic studies revealed that the cycloisomerization of 1,11-enynes underwent copper-catalyzed 2,3-rearrangement, [3 + 2] cycloaddition, and 1,2-O migration in a one-pot reaction. The present method highlights a broad substrate scope and good functional group tolerance, the formation of two six-membered rings and two or three stereocenters, an unexcepted 1,2-O migration, and a novel chromeno[4,3-<i>d</i>][1,3]oxazine scaffold.