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N to C Aryl Migration in Lithiated Carbamates: α-Arylation of Benzylic Alcohols

2009; American Chemical Society; Volume: 131; Issue: 10 Linguagem: Inglês

10.1021/ja808959e

1943-2984

Jonathan Clayden, William Farnaby, D.M. Grainger, Ulrich Hennecke, Michele Mancinelli, Daniel J. Tetlow, Ian H. Hillier, Mark A. Vincent,

Chemical synthesis and alkaloids

We report a new mode of reactivity displayed by lithiated O-benzyl carbamates carrying an N-aryl substituent: upon lithiation, the N-aryl group is transferred cleanly from N to C. An arylation of the carbamate results, providing a route to alpha,alpha-arylated secondary or tertiary alcohols. We also report density functional theory calculations supporting the proposal that arylation proceeds through a dearomatizing attack on the aromatic ring, a significantly lower energy pathway than the 1,2-acyl transfer observed with related N-alkyl carbamates.