Nucleophilic Addition of Amines to Ruthenium Carbenes: ortho-(Alkynyloxy)benzylamine Cyclizations towards 1,3-Benzoxazines

摘要

A new ruthenium-catalyzed cyclization of ortho-(alkynyloxy)benzylamines to dihydro-1,3-benzoxazines is reported. The cyclization is thought to take place via the vinyl ruthenium carbene intermediates which are easily formed from [Cp*RuCl(cod)] and N2CHSiMe3. The mild reaction conditions and the efficiency of the procedure allow the easy preparation of a broad range of new 2-vinyl-2-substituted 1,3-benzoxazine derivatives. Rearrangement of an internal C(sp) in the starting material into a tetrasubstituted C(sp(3)) atom in the final 1,3-benzoxazine is highly remarkable.