A Barton nitrite ester-type remote functionalization and cyclization of N-nitrosobenzamides

An efficient Barton nitrite ester-type cyclization reaction of N-ethyl-N-nitrosobenzamides to synthesize benzo[d][1,2]oxazin-1-ones was established. The reaction proceeds via the homogeneous cleavage of N-N bonds to neutrally generate a nitrogen-centered radical with an intramolecular H-atom transfer (HAT) occurring in a highly efficient way. Interestingly, the N-nitrosobenzamides are converted to the corresponding & gamma;-hydroxy oximes in the reaction first, and then a nucleophilic attack occurs to afford the desired benzo[d][1,2]oxazin-1-ones efficiently.