One-pot synthesis of 2,3-disubstituted dihydrobenzofurans and benzofurans via rhodium-catalyzed intramolecular C–H insertion reaction

Abstract

Intramolecular sp(3) C-H insertion reaction of α-imino rhodium carbene generated from N-sulfonyl-1,2,3-triazoles has been described. A number of 2,3-dihydrobenzofuran and benzofuran derivatives have been obtained in good to excellent yields.

Rhodium(II)‐Catalysed Skeletal Rearrangement of Ether Tethered N‐Sulfonyl 1,2,3‐Triazoles: a Rapid Approach to 2‐Aminoindanone and Dihydroisoquinoline Derivatives

“…Recently, N ‐sulfonyl‐1,2,3‐triazoles, which can be easily prepared by a copper‐catalysed 1,3‐dipolar cycloaddition of terminal alkynes with N ‐sulfonyl azides,7 have received considerable attention to serve as precursors of azavinyl carbenes 8,9. Besides the common reactivity, such as cyclopropanation,8a,9g XH insertion,8g,9c,l,m and ylide formation,9a,b,g α‐imino rhodium carbenes can be employed as three‐atom units to participate in stepwise cycloadditions, giving various N‐heterocycles 8d–g. As part of our interest in N‐heterocycle synthesis via azavinyl metal carbenes,10 we envision that an α‐imino rhodium carbene generated from N ‐sulfonyl‐1,2,3‐triazole 1 which has an ether tether, may undergo tandem transformations, involving cleavage of the CO bond and building up of new CO and CN bonds, and eventually result in the formation of a dihydroisoquinoline 2 .…”

Recent Advances in Synthetic Strategies to 2,3-Dihydrobenzofurans

“…Wan, Chen, and co-workers (2015) reported the reaction of 4-(2-(benzyloxy)aryl)-1-tosyl-1,2,3-triazoles with catalytic Rh 2 (S-PTV) 4 to generate an -imino rhodium carbene that underwent an intramolecular sp 3 C-H insertion reaction to give 3-[(tosylamino)methylene]-DHBs. 100 In this case various DHBs bearing an exocyclic double bond and versatile functional groups were obtained in good to excellent yields (Scheme 34).…”

Catalytic Insertion Reactions of α‐Imino Carbenoids

“…In early 2014, Wang and Chen described a Rh 2 (S-PTV) 4 C8 catalyzed methodology for the efficient synthesis of benzofuran derivatives 29 from 2-(alkoxy)phenyl substituted 1-tosyl-1H-1,2,3triazoles (Scheme 7a). [19] Notably, steric and electronic factors played an important role for illustrating the reactivity, as sterically hindered or electronically poor R 1 containing substrates provided the corresponding products in low yields. In addition, as expected primary CÀ H bond was found to be much inert towards insertion than the secondary CÀ H bond and benzyl CÀ H bonds.…”