Regio- and Diastereoselective Construction of Functionalized Benzo[b]oxepines and Benzo[b]azepines via Recyclable Gold(I)-Catalyzed Cyclizations

Abstract

The heterogeneous gold-catalyzed cyclization of (oalkynyl)phenoxy-or N-(o-alkynylphenyl)tolylsulfonamidoacrylates with alcohols has been developed by using an MCM-41-anchored diphenylphosphine-Au(I) complex [MCM-41-Ph 2 P-AuNTf 2 ] as the catalyst under mild reaction conditions, yielding diverse functionalized benzo[b]oxepines or benzo [b]azepines with good to high yields and excellent diastereoselectivity. This heterogenized gold(I) catalyst exhibits a comparable activity to homogeneous Ph 3 PAuNTf 2 and can be facilely recovered by a simple filtration of the reaction solution and reused more than seven times with almost a consistent catalytic efficiency.

Dodging the Conventional Reactivity of o-Alkynylanilines under Gold Catalysis for Distal 7-endo-dig Cyclization

“…The 7- endo - dig cyclization is preferred over the 5- endo - dig aza- and 6- exo - dig carba- cyclization modes. During the preparation of this manuscript, Cai and co-workers reported the synthesis of substituted dihydrobenzo­[ b ]­azepines and dihydrobenzo­[ b ]­oxepines from vinylogous carbamates derived from o -alkynylanilines and vinylogous carbonates derived from o -alkynylphenols, respectively, using a heterogeneous gold­(I) catalyst . In our experiments, the substrate vinylogous amides derived from o -alkynylanilines showed a slightly different reactivity and resulted in benzo­[ b ]­azepines.…”

Base-promoted cyclization ofortho-hydroxyacetophenones within situgenerated cyclopropenes: diastereoselective access to spirobenzo[b]oxepines and related precursors

“…This may be due to the unfavorable entropic penalties and the unavoidable transannular interactions during their formation. 6 In view their pharmacological importance and synthetic challenges, chemists have made great efforts to search for straightforward techniques for obtaining a large molecular diversity of functionalized benzo[ b ]oxepines, 1–5,7–18 for example, the intramolecular Mitsunobu reaction of phenols, 8 the Friedel–Crafts cyclization of aryloxybutanoic acid 9 and ring-closing metathesis (RCM) of dienes 10 have been traditionally used for the construction of these hybrid frameworks. However, the described methods have one or more critical shortcomings, such as narrow substrate scope, difficult-to-access starting materials, poor yields, etc ., which limit the progression of the field.…”

“…Alternatively, most innovative routes toward a diverse set of structurally complex benzo[ b ]oxepines rely on transition metal-catalyzed inter- and intramolecular cyclization reactions involving various coupling precursors. 11–18 They include the [5 + 2] annulation of 2-acyl/aroylmethoxyarylboronic acids 11 / ortho -vinylphenols 12 with allenoates/alkynes catalyzed by Pd( ii )-/Rh( iii )-complexes, Fe( iii )-catalyzed alkyne–aldehyde metathesis, 13 Sc( iii )-catalyzed ring-expansion of oxetane, 14 7- endo -heterocyclization of aromatic alkynols using the Os( iv )-catalyst, 15 Au( i )/Ir( i )-catalyzed intramolecular cyclization of ( ortho -alknylaryloxy)acrylates 16 / ortho-O -propargyl-substituted arylenaminones 17 / ortho-O -allyl-substituted arylenaminones, 18 etc . Besides, simple base-assisted formal [4 + 3] annulation for accessing benzo[ b ]oxepines was also well established by taking bromophenylacetonitriles/2-fluorophenylacetylenes as 4C units for oxepine ring synthesis.…”

Recyclable gold(i)-catalyzed heterocyclization of ynamides with benzyl or indolyl azides towards 2-aminoindoles or 3-amino-β-carbolines

“…21 Recently, several ligand-modified MCM-41-grafted gold( i ) or gold( iii ) complexes have found important applications in diverse organic transformations. 22 Compared to MCM-41, SBA-15 possesses thicker framework walls, higher hydrothermal stability, and much bigger pore diameter between 5 and 30 nm, which can facilitate diffusion of organic molecules inside the channels. 23 Although mesoporous SBA-15-supported iridium, palladium, platinum, and rhodium complexes have been successfully applied for some important organic reactions, 24 the synthesis and applications of SBA-15-immobilized gold complexes have not been explored until now.…”