Regioselective Preparation of Benzo[b]furans from Phenols and α-Bromoketones

Abstract

In this paper, a fully regiocontrolled synthesis of either 2- and 3-substituted benzo[b]furans is described. Direct reaction between phenols and α-bromoacetophenones in the presence of neutral alumina yields 2-substituted benzo[b]furans with complete regiocontrol. When a basic salt such as potassium carbonate is used, the corresponding 2-oxoether is obtained. Cyclization of these latter compounds promoted by neutral alumina yields the corresponding 3-substituted benzo[b]furans. Using the former method, Moracin M and other analogues can be obtained from commercial sources in two preparative steps. DFT calculations provide reasonable reaction paths to understand the formation of 2-substituted benzo[b]furans.

Total synthesis of the 2-arylbenzo[b]furan-containing natural products from Artocarpus

“…29 Global deprotection of intermediate 34 conveniently completed the total synthesis of another natural product moracin M (4) with an overall yield of 56.2% (6 steps), which was higher yields than recent synthetic method (2 steps in 6.5% total yield) by Cossío and co-workers in 2012. 27 Moracin D (3) can be obtained from moracin C (1) by using the published procedures, 34 but in view of weaker LOXs inhibitory activities of moracin D, we haven't carry out this reaction in our laboratory. Besides, the reuse of the starting material 18 and the intermediate 33 can get another natural product artoindonesianin B-1 (2) with an overall yield of 11.3% (8 steps, Scheme 3).…”

Facile Synthesis of Natural Moracin Compounds using Pd(OAc)2/P(tBu)3-HBF4as a Sonogashira Coupling Reagent

“…Demethylation of 9 using BBr 3 produced the moracin M in 25% yield as same as literature. 13 The intermediate benzofuran 9 was utilized for the first synthesis of moracin N (13) which was isolated from mulberry 20 and showed tyrosinase inhibitory activity 21 and better antifungal activity 22 than moracin M. Propargylation of 9 with 3-chloro-3-methylbutyne and following reduction using Lindlar catalyst gave the prenyl ether 11. Water-accelerated [3,3]sigmatropic rearrangement 23 of 11 produced 5-propenylbenzofuran 12 in 47% yield regioselectively, and followed demethylation of 12 using BBr 3 gave the moracin N in 21% yield.…”

Di‐tert‐butylneopentylphosphine (DTBNpP): An Efficient Ligand in the Palladium‐Catalyzed α‐Arylation of Ketones

“…[18] The reaction is proposed to proceed through alumina-promoted hemiacetal formation followed by electrophilic aromatic substitution to form the C-C bond. [18] The reaction is proposed to proceed through alumina-promoted hemiacetal formation followed by electrophilic aromatic substitution to form the C-C bond.…”