Mechanisms of tetrazole formation by addition of azide to nitriles.
It is well-known that azide salts can engage nitriles at elevated temperatures to yield tetrazoles; however, there is continued debate as to the mechanism of the reaction. Density functional theory calculations with the hybrid functional B3LYP have been performed to study different mechanisms of tetrazole formation, including concerted cycloaddition and stepwise addition of neutral or anionic azide species. The calculations presented here suggest a previously unsuspected nitrile activation step en route to an imidoyl azide, which then cyclizes to give the tetrazole. The activation barriers are found to correlate strongly with the electron-withdrawing potential of the substituent on the nitrile.
Himo
Fahmi
F
Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
Demko
Zachary P
ZP
Noodleman
Louis
L
Sharpless
K Barry
KB
D001386:Azides / Q000737:chemistry*; D003500:Cyclization; D008958:Models, Molecular; D009570:Nitriles / Q000737:chemistry*; D013777:Tetrazoles / Q000138:chemical synthesis*; D013816:Thermodynamics
D001386:Azides; D009570:Nitriles; D013777:Tetrazoles