T. Krüger, A. Kelling, U. Schilde, T. Linker
Simple Synthesis of γ-Spirolactams by Birch Reduction of Benzoic Acids
Eur. J. Org. Chem. 2017, 1074-1077
DOI: 10.1002/ejoc.201601650
A convenient synthesis of γ-spirolactams in only two steps is described. Birch reduction of benzoic acids and immediate alkylation with chloroacetonitrile afford cyclohexadienes in high yields. The products can be isolated by crystallization on a large scale in analytically pure form. Subsequent hydrogenation with platinum(iv) oxide as catalyst reduces the nitrile and the double bonds in the same step and with excellent stereoselectivity. The relative configurations have been determined unequivocally by X-ray analyses. Direct cyclization of the intermediary formed amino acids affords the desired γ-spirolactams in excellent overall yields. The procedure is characterized by few steps, cheap reagents, and can be performed on a large scale, interesting for industrial processes.
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