Conjugate Additions of sp2 Hybridized Nitrogen Nucleophiles to ortho-Quinone Methides

Ortho-quinone methides (o-QMs) are highly reactive electrophiles, which have been well used in chemical synthesis. Our group developed a base-promoted method to generate o-QMs in-situ. In this thesis, novel conjugate additions of sp2 hybridized nitrogen nucleophiles towards o-QMs will be discussed. In the first part of this presentation, a three-component synthesis of 3,4-dihydro-2H-1,3-benzoxazines is described. This reaction demonstrates an unusual reactivity of imines as nitrogen nucleophiles in the event of C-N bond formation. In the second part, conjugate addition of dihydrooxazoles derivatives is presented. The reaction is believed to proceed through long-lived iminium intermediates. Subsequent stereoelectronically controlled, regioselective hydrolysis generates a variety of benzylic amino-esters as kinetic products. Potential application in synthesis of natural products will be discussed. Lastly, the on-going development of a recoverable chiral auxiliary that enables asymmetric syntheses of bnenzylic amines via benzoxazines is described