Rh(iii)-catalyzed C–H activation/cyclization of benzamides and diazo compounds to form isocoumarins and α-pyrones

Abstract

Rhodium-catalyzed intermolecular cyclization of benzamides and diazo compounds via C-H activation has been achieved to construct C-C/C-O bonds for the first time. The process provides a facile approach for the construction of isocoumarins and α-pyrones without the need for high temperature or adding oxidants.

Rh(III)- and Ir(III)-Catalyzed C–C Bond Cross Couplings from C–H Bonds

“…Asymmetric version was subsequently reported by Cramer [105]. Besides, carbonyl-containing diazo precursors (Scheme 8b, c) or diazotized Meldrum's acid (Scheme 8d), used as "two-carbon components," enables tandem C-H activation/cyclization/condensation reaction sequence delivering valuable heterocyclic skeletons like isoquinolines and pyridine N-oxides [106], isocoumarins and α-pyrones [107], cinnolin-3(2H )-one derivatives [108], or Nmethoxyisoquinolinediones [109]. Finally, C-H activation/[4+3] cycloaddition cascade transformations could be envisioned in the presence of vinylcarbenoids, hence enabling the expedient construction of generally difficult-to-prepare sevenmembered azepinone scaffolds (Scheme 8e) [110].…”

Isocoumarins: General Aspects and Recent Advances in their Synthesis

“…Furthermore, Liu and co‐workers reported a Rh(III)‐catalyzed C–H activation and annulation reaction of benzamides with diazo compounds for the synthesis of 3,4‐disubstituted isocoumarins [Scheme , Eq. (1)] . Shang and co‐workers developed a Rh(III)‐catalyzed reaction of benzoic acids and cyclic diazo‐1,3‐diketones which proceeds via domino intermolecular C–H activation and intramolecular esterification reactions for the synthesis of isocoumarins [Scheme , Eq.…”

Rhodium(III)‐Catalysed Carbenoid C(sp2)–H Functionalisation of Aniline Substrates with α‐Diazo Esters: Formation of Oxindoles and Characterisation/Utility of an Intermediate‐Like Rhodacycle

“…Following the seminal work of Rovis et al, Cui and co‐workers developed a protocol for the synthesis of azepinone derivatives through the Rh III ‐catalysed C–H activation of benzamides with vinyl carbenoids . More recent reports of Rh III ‐catalysed C–H functionalisation using diazo compounds as coupling partners have come from the groups of Glorius, Wang, Chang, Xu and Yi, Liu, Zhou, Kim, Lee, Zeng, and Samanta . Although decent progress has been made in this area, we believe that such an interesting topic is worthy of further exploration.…”