Transition-metal-free regioselective synthesis of spiro-oxazolidines through [3 + 2] annulation reactions of azadienes with haloalcohols

The transition-metal-free regioselective [3 + 2] annulation of azadienes with haloalcohols for the preparation of highly functionalized spiro-oxazolidines is experimentally simple and proceeds under mild conditions. The metal-free protocols have more significance than the metal-catalyzed ones when the toxicity associated with the metal catalyst is considered. This transformation features a broad substrate scope, good yields, and excellent regioselectivity. Moreover, large-scale synthesis and representative transformations of spiro-oxazolidines were carried out to provide additional evidence on the practicality of this approach.