Copper‐Catalyzed Aqueous N−O Bond Cleavage of 2‐Oxa‐3‐Azabicyclo Compounds to Cyclic cis‐1,4‐Amino Alcohols

Abstract

The N−O bond cleavage of 2‐oxa‐3‐azabicyclo substrates, which are readily prepared by the hetero Diels‐Alder reaction between nitroso dienophiles and cyclic 1,3‐dienes, was effectively catalyzed by heterogeneous copper‐on‐carbon (Cu/C) under aqueous conditions to give the corresponding cyclic cis‐1,4‐amino alcohol derivatives. The present method was applied to the direct incorporation of the hydroxy and amino groups derived from a nitroso substrate into cyclic 1,3‐dienes with cis‐selectivity by the combination of the in situ formation of 2‐oxa‐3‐azabicyclo compounds and following Cu/C‐catalyzed N−O bond cleavage. The obtained cis‐4‐aminocyclohexenols, derived from cyclohexadiene as a cyclic 1,3‐diene, could be selectively oxidized by using the ruthenium‐on‐carbon (Ru/C) catalyst under oxygen atmosphere to the corresponding 4‐aminocyclohexenones at 50–65 °C or para‐iminoquinones at 100–110 °C as useful reactive synthetic precursors.

Copper-catalyzed synthesis of primary amides through reductive N–O cleavage of dioxazolones

“…Several reductive N-O bond cleavage of isoxazolines and 2-oxa-3-azabicyclic compounds have been studied using copper(0) nanoparticle and heterogeneous copper-on-carbon in the absence of silane. 54,55 It is noteworthy that the reaction without silane gave trace amount of amide, indicating the use of silane is essential (entry 9). To conrm that the reaction was not possible, several control experiments were further performed, which indicated that the copper catalyst was pivotal (entry 12 and 13).…”