N-Ethynylation of Anilides Decreases the Double-Bond Character of Amide Bond while Retaining trans-Conformation and Planarity.
Chemistry, 2019/8/01;25(43):10118-10122.
Yamasaki R[1], Morita K[1], Iizumi H[1], Ito A[1], Fukuda K[1], Okamoto I[1]
Affiliations
PMID: 31050845DOI: 10.1002/chem.201901451
Impact factor: 5.02
Abstract
Activated amide bonds have been attracting intense attention; however, most of the studied moieties have twisted amide character. To add a new strategy to activate amide bonds while maintaining its planarity, we envisioned the introduction of an alkynyl group on the amide nitrogen to disrupt amide resonance by nN→Csp conjugation. In this context, the conformations and properties of N-ethynyl-substituted aromatic amides were investigated by DFT calculations, crystallography, and NMR spectroscopic analysis. In contrast to the cis conformational preference of N-ethyl- and vinyl-substituted acetanilides, N-ethynyl-substituted acetanilide favors the trans conformation in the crystal and in solution. It also has a decreased double bond character of the C(O)-N bond, without twisting of the amide. N-Ethynyl-substituted acetanilides undergo selective C(O)-N bond or N-C(sp) bond cleavage reactions and have potential applications as activated amides for coupling reactions or easily cleavable tethers.
Keywords: acylation; alkynes; amides; conformational analysis; ynamides
More resources
EndNote: Download