Salicylaldehydes condense with simple secondary amines to form dihydro-1,3-benzoxazine structures in high yield without the need for metal catalysts.  This amine a-C-H functionalization is shown to occur under generally mild conditions and in some instances at room temperature.  The mechanism has been elucidated by DFT calculations that correlate well with experimental observations.  At elevated temperatures these cyclic N,O-acetals are shown to fragment into cyclic imines and o-quinone methides, the latter being susceptible to nucleophilic attack by a second equivalent of amine, furnishing benzylic amine structures.

Redox-neutral a-oxygenation of amines

247th National Meeting (2014)

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