A Facile One‐Pot Access to Dibenzo[b,e]oxepines by a Lewis Acid Catalysed Tandem Reaction

Abstract

Dibenzo[b,e]oxepine derivatives have been constructed efficiently by one‐pot tandem carbon–carbon bond formation reactions. First, 2‐(3,5‐dimethoxybenzyloxy)benzaldehydes were treated with various nucleophiles under I2 catalysis and then 1‐(3,5‐dimethoxybenzyloxy)‐3,5‐dimethoxybenzene was treated with several aromatic as well as heteroaromatic aldehydes under BF3·Et2O catalytic conditions to provide dibenzo[b,e]oxepines in good yields.

Recent Advances on the Development of Synthetic Strategies to Access Dibenzoxepine Derivatives

“…In 2011, Reddy and co-workers demonstrated an acidcatalyzed tandem reaction for the construction of 11substituted dibenzo [b,e]oxepines 15 and 18 via a nucleophilic addition/Friedel-Crafts-type cyclization reaction (Schemes 4 and 5). 13 They reported two ways for the construction of the 11-substituted dibenzo [b,e]oxepines. Firstly, O-(benzyloxy)salicylaldehyde 13 was reacted with various nucleophiles 14 in the presence of iodine catalyst to afford dibenzo [b,e]oxepines 15 in moderate to good yields (Scheme 4); the nucleophiles were electron-rich aromatics and 1,3-dicarbonyl compounds.…”

“…A plausible mechanism for the formation of 15 is depicted in Scheme 6. 13 Initially, iodine reacts with aldehyde 13 followed by nucleophilic addition of 14 on to the aldehyde to form intermediate II. Subsequently, intermediate II undergoes intramolecular Friedel-Crafts-type cyclization via the formation of a benzylic cation III leading to dibenzoxepine 15.…”

“…Scheme 4 Iodine-catalyzed Synthesis of Dibenzo[b,e]oxepine DerivativesSimilarly, based on the development for the synthesis of dibenzoxepine 15 via the tandem method, they performed another reaction with a strong electron-rich substrate 16 and external aldehydes 17 to access a library of 11-substituted dibenzo[b,e]oxepines 18 in the presence of BF3.Et2O catalyst in good to excellent yields (Scheme 5) [13]. …”

Pd/C and TFA‐promoted One‐pot, Two‐step Cascade Reaction: An Effective Synthesis of Oxepines

“…successfully developed FeCl 3 ‐catalyzed alkyne‐aldehyde metathesis process for the synthesis of acylated dibenzo[ b,f ]oxepines from 2‐(2‐(phenylethynyl)phenoxy)benzaldehyde derivatives. Recently, synthesis of bioactive oxepines were reported by Nishino et al ., [15] Guy et al ., [16] Heo et al [17] . and Mohapatra et al [18] …”

Efficient Synthesis of 4,7-Dihydro-1H-oxepino[2,3-c]pyrazoles by Potassium Carbonate Promoted [4+3] Annulation of Crotonate-Derived Sulfur Ylides with Benzylidenepyrazolones

“…They are found in many natural products, ranging from the well-known radulanins 1 and heliannuol D, 2 in liverwort and sunflower extracts, to the sneezewood-derived oxepino[3,2-g]chromones karenin, ptaeroxylin and ptaeroxylinol, 3 and some of the most interesting members of the epidithiodiketopiperazine family as represented by aranotin ( Figure 1). 4 A variety of synthetic methods have been developed to construct the seven-membered oxepines, such as cycloaddition, 5 transition-metal-catalyzed olefin metathesis, 6 ring-closing metathesis, 7 and acid-catalyzed cyclization, 8 among others. 9 Despite such progress, the synthesis of related natural products, in which the dihydrooxepine unit is highly functionalized, remains challenging, in part because the scope and generality of existing methods are rather limited.…”