Sequential one-pot method for oxy-Michael addition, Heck coupling, and degradation followed by condensation: facile synthesis of 2-benzoxepin-3(1H)-ones

Exciting progress in the transition metal‐catalyzed synthesis of oxepines, benzoxepines, dibenzoxepines, and other derivatives

“…The synthesis of functionalized 2‐benzoxepin‐3‐(1 H )‐ones 119 is reported via a sequential one‐pot process by Reddy et al in 2013 (Scheme 32). [ 73 ] In this procedure, C–O and C–C bond formation occurred due to the oxy‐Michael addition and palladium‐catalyzed Heck coupling reaction. The final benzoxepine product is resulted through a retro‐oxy‐Michael addition followed by condensation reaction (Scheme 33).…”

Concise Three-Step Strategy for the Synthesis of 2-Benzoxepin-3(1H)-ones

“…11 As a part of our interest in transition-metal catalysis, we previously developed a onepot method for the synthesis of cinnamate diesters via intermolecular oxy-Michael addition and subsequent intermolecular Heck coupling of 2-bromobenzyl alcohols with Michael acceptors; 12 this method was successfully applied to the synthesis of 2-benzoxepin-3(1H)-ones. 13 In this method, the base-promoted condensation of cinnamate diesters to give 2-benzoxepin-3(1H)-ones involves an interesting reaction path: (1) retro-oxy-Michael addition, 14 (2)…”

“…To begin with o-bromobenzaldehydes or o-bromoacetophenones 1 were identified as suitable starting materials. 16 Since, ethyl cinnamates 13 undergo smooth condensation to give 2-benzoxepin-3(1H)-ones 7, the palladium-catalyzed intermolecular Heck coupling using 1a and 1aa as model substrates with ethyl acrylate was examined under different conditions (Table 1). 17 Performing the reaction of 1a with ethyl acrylate with palladium(II) acetate (5 mol%) as the catalyst and triphenylphosphine (10 mol%) as the ligand in acetonitrile with cesium carbonate as the base gave the aldol product 3 exclusively, albeit in poor yield (entry 1).…”

“…The 2-bromobenzaldehydes 1a-h were synthesized using the reported procedure for the bromination of the corresponding benzaldehydes. 16 Compounds 1aa, 22 1cc, 23 1gg, 24 1hh, 25 4g and 6a-hh, 13 3, 26 2a, 2c, 4a, and 2aa, 27 2g and 2f, 28 2cc and 4cc 17a are known in the literature.…”