Synthesis of tetracyclic dibenzo[b,f][1,4]oxazepine-fused β-lactams via visible-light-induced Staudinger annulation

Abstract

An efficient visible-light-induced Staudinger [2+2] annulation reaction between α-diazo ketones and dibenzo[b,f][1,4]oxazepine/thiazepine-imines under catalyst-free conditions has been developed. This protocol provides a facile method to synthesize tetracyclic dibenzo[b,f][1,4]oxazepine/thiazepine-fused β-lactams bearing...

Recent Progress in Transformations of Azepine/Oxazepine/Thiazepine Derivatives

“…In 2023, a Staudinger reaction between dibenzo[ b , f ][1,4]oxa‐/thiazepines 1 , 11 and α‐diazo ketones 51 was carried out under visible light irradiation (Scheme 19). [43] In this procedure, a series of dibenzo[ b , f ][1,4]oxa‐/thiazepine‐fused β‐lactam frameworks 52 , 53 were synthesized under catalyst‐free conditions. The desired product was also achieved under solar light in 97 % yield.…”

“…In 2023, a Staudinger reaction between dibenzo[b,f][1,4]oxa-/thiazepines 1, 11 and α-diazo ketones 51 was carried out under visible light irradiation (Scheme 19). [43] In this procedure, a series of dibenzo…”

Photoinduced arylative formal 4-endo-dig cyclization of propargyl alcohols/amines to access strained heterocycles

“…Formation of a 4-membered ring via intramolecular Michael addition has not been reported to date because of the obvious fact that such small ring closure requires passing a high transition state energy. Note that azetidines are usually formed from imines through aza-Paternò–Büchi cyclization (and some other approaches 18,19 ), whereas, herein, we demonstrate a complementary approach utilizing propargyl amines, the normal Paternò–Büchi reaction, and a ring opening/closing cascade. This annulation cyclization was equally extendable to 5-membered oxa/aza cycles (oxolanes and pyrrolidines) 20 through an appropriate disposition of a nucleophile in precursors (homo propargylic systems).…”