Structures of N, N-dialkoxyamides: Pyramidal anomeric amides with low amidicity

Abstract

The first X-ray structures of two anomeric N,N-dialkoxyamides (2 and 3) have been obtained, which confirm that they are highly pyramidalized at nitrogen and have long N - CO bonds, a characteristic of other anomeric amides and a consequence of drastically reduced amidicity. The crystals also demonstrate chirality at the amide nitrogen in the solid state. The structures are well-predicted by density functional calculations using N,N-dimethoxyacetamide as a model. The amidicity of N,N-dimethoxyacetamide has been estimated by two independent methods, COSNAR and a new transamidation method, which give almost identical resonance stabilization energies of - 8.6 kcal mol -1 and only 47% that of N,N..