Nitrosobenzene: Reagent for the Mitsunobu Esterification Reaction

Abstract

Nitrosobenzene has been demonstrated to participate in the Mitsunobu reaction in an analogous manner to dialkyl azodicarboxylates. The protocol using nitrosobenzene and triphenylphosphine (1:1) under mild conditions (0 °C) provides the ester derivatives of aliphatic and aromatic acids using various alcohols in moderate yield and with good enantioselectivity, giving the desired products predominantly with an inversion of configuration. The proposed mechanism, which is analogous to that observed using dialkyl azodicarboxylates, involves a nitrosobenzene–triphenylphosphine adduct and an alkoxytriphenylphosphonium ion and was supported by density functional theory calculations, 31 P NMR spectroscopy, and experiments conducted with isotopically labeled substrates.

Efficient Buchwald–Hartwig and nitrene-mediated five-membered ring closure approaches to the total synthesis of quindoline. Unexpected direct conversion of a nitro group into a phosphazene

“…26 Further, their formation has been recently demonstrated by low temperature 31 P NMR spectroscopy, 27 and they were also proposed as key intermediates during the Mitsunobu esterification of alcohols mediated by nitrosobenzene. 28…”

“…26 Further, their formation has been recently demonstrated by low temperature 31 P NMR spectroscopy, 27 and they were also proposed as key intermediates during the Mitsunobu esterication of alcohols mediated by nitrosobenzene. 28 The formation of the betaine intermediate from i through the TSi involves an activation energy of 15.46 kcal mol −1 , with an endothermic balance for ii of 0.55 kcal mol −1 . Aerwards, the ring closure of ii to obtain iii shows that the balance of these two intermediates has a thermodynamic penalty of 8.53 kcal mol −1 through iii.…”