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Paper | Special issue | Vol 79, No. 1, 2009, pp.985-1005
Published online, 16th December, 2008
DOI: 10.3987/COM-08-S(D)76
Synthesis of Macrocyclic Lactams from 2-(ω-Aminoalkyl)-2-benzoylamino-3-phenyl-N,N-dimethylpropanamides via Direct Amide Cyclization

Stephan P. Fritschi, Anthony Linden, and Heinz Heimgartner*

*Institute of Organic Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland

Abstract

The alkylation of 4-benzyl-2-phenyl-1,3-oxazol-5(4H)-one (11) with ω-azidoalkyl iodides (12) by deprotonation with LDA in THF/HMPT at –78 °C yielded mixtures of the 4,4-disubstituted 1,3-oxazol-5(4H)-ones (13) and the O-alkylated 1,3-oxazoles (14) in 65–50%, with 13 as the major product. The reaction of the latter with dimethylamine in acetonitrile at room temperature led to ω-azido-2-benzamido-2-benzylalkane amides (15), which were reduced to give the corresponding ω-amino derivatives (16). On treatment with HCl gas or BF3 in boiling toluene, the macrocyclic 2-benzamido lactams (18) were formed in up to 27% yield via the intermediate formation of 1,3-oxazol-5(4H)-ones (17). The structures of the 14- and 15-membered lactams have been established by X-ray crystallography.