Rh(III)-Catalyzed C–H Activation/[3 + 2] Annulation of N-Phenoxyacetamides via Carbooxygenation of 1,3-Dienes

Abstract

A unique Rh­(III)-catalyzed C–H activation/[3 + 2] annulation of N-phenoxyacetamides has been developed for the construction of dihydrobenzofurans via carbooxygenation of 1,3-dienes. This transformation features a redox-neutral process with specific chemoselectivity, good substrate/functional group compatibility, and profound synthetic potentials. A preliminary exploration to realize their asymmetric synthesis have been also successfully demonstrated, which further strengthens the practicality of this approach.

Cobalt-Catalyzed Z to E Geometrical Isomerization of 1,3-Dienes

“…Preparation was according to the general procedures to give 2.54 g (17.2 mmol, 86% yield) of the desired product 1s as a colorless oil. For ( E )-isomer: 1 H NMR: (500.0 MHz, CDCl 3 ) δ 7.45–7.50 (m, 1H), 7.15–7.21 (m, 1H), 6.99–7.13 (m, 2H), 6.81–6.89 (m, 1H), 6.71 (d, J = 11.5 Hz, 1H), 6.47–6.58 (m, 1H), 5.36 (d, J = 17.0 Hz, 1H), 5.21 (d, J = 10.0 Hz, 1H); for ( Z )-isomer: 1 H NMR: (500.0 MHz, CDCl 3 ) δ 7.32–7.38 (m, 1H), 7.20–7.26 (m, 1H), 6.99–7.13 (m, 2H), 6.68–6.78 (m, 1H), 6.48 (d, J = 11.5 Hz, 1H), 6.32–6.40 (m, 1H), 5.40 (d, J = 17.0 Hz, 1H), 5.24 (d, J = 10.0 Hz, 1H).…”

“…Preparation was according to the general procedures to give 2.54 g (17.2 mmol, 86% yield) of the desired product 1s as a colorless oil. For (E)isomer: 32 5-(Buta-1,3-dien-1-yl)benzo [d][1,3]dioxole (1t, E/Z = 46/54). Preparation was according to the general procedures to give 2.68 g (15.4 mmol, 77% yield) of the desired product 1t as a colorless oil.…”

Recent advances in transition metal-catalyzed heteroannulative difunctionalization of alkenes via C–H activation for the synthesis of heterocycles

“…Recently, rhodium-catalysed C–H activation and [3 + 2] annulation of N -phenoxyacetamides 86 with 1,3-dienes 87 was developed by Yi and co-workers (Scheme 40). 59 This reaction provided facile access to dihydrobenzofurans 88 with specific regioselectivity under redox-neutral conditions. This protocol tolerated a wide range of functional groups and exhibited the advantages of profound synthetic utility.…”

Rhodium-Catalyzed Annulation of Vinylated Tyrosines with Internal Alkynes to Access Oxepine-Mounted Unnatural Tyrosines and Its Peptide Late Stage Functionalization

“…However, efficient strategies involving mounting a heterocyclic moiety on the aryl moiety of tyrosine are scarce. Recently, one such example was disclosed by Zhou and co-workers when they unveiled the [3+2] annulation of N -phenoxyacetamides with 1,3-dienes, whereby the C­(sp 2 )–H modification of N -Boc-protected tyrosine methyl ester was achieved by its annulation with 1-phenylbuta-1,3-diene to furnish a tyrosine-based dihydrobenzofuran derivative in 53% yield under Rh catalysis (Scheme b) . In addition, several Rh-catalyzed strategies for the C–H functionalization of alkenes have been developed by pioneering scientists in recent years .…”

“…Recently, one such example was disclosed by Zhou and coworkers when they unveiled the [3+2] annulation of Nphenoxyacetamides with 1,3-dienes, whereby the C(sp 2 )−H modification of N-Boc-protected tyrosine methyl ester was achieved by its annulation with 1-phenylbuta-1,3-diene to furnish a tyrosine-based dihydrobenzofuran derivative in 53% yield under Rh catalysis (Scheme 1b). 12 In addition, several Rh-catalyzed strategies for the C−H functionalization of alkenes have been developed by pioneering scientists in recent years. 13 However, the late stage functionalization of tyrosinecontaining peptides by the existing annulation strategies on phenols remains unexplored.…”