Rhodium(II) Acetate-catalysed Decomposition of 2-Diazo-3-oxobutanamides Derived from L-Phenylalanine

Article abstract of DOI:10.1002/prac.19953370160

In order to developed a practical method for alkylating α-amino acids at the α- or β-carbon atom by intramolecular carbene C-H insertion, a series of diazoamides 3a-e was synthesized and subjected to rhodium(II) acetate-catalysed decomposition.The N-benzyl derivative 3a gave mainly the azetidinones 4a and 5a, resulting from a carbene C-H insertion into the N-benzyl group.The N-diphenylmethyl derivative 3c yielded, upon treatment with rhodium(II) acetate, the azetidinone 5c, the imine 6c, the cycloheptapyrrolidinone 7c as well as the desired pyrrolidinone 8c (12percent yield) the latter resulting from an alkylation of the L-phenylalanine framework at the β-carbon atom.