Pd(II)-Catalyzed Synthesis of Alkylidene Phthalides via a Decarbonylative Annulation Reaction

Abstract

An unprecedented Pd­(II)-catalyzed decarbonylative C–H/C–C activation and annulation reaction, which proceeds via intramolecular cyclization, is reported. This reaction of hydroxynaphthoquinones with disubstituted alkynes provides good yields of substituted alkylidene phthalides, which are the key intermediates for the synthesis of bioactive natural products.

Copper/Iodine‐Cocatalyzed C‐C Cleavage of 1,3‐Dicarbonyl Compounds Toward 1,2‐Dicarbonyl Compounds

“…On the basis of the present results and the precedent results, we propose that the reaction is initiated by coordination of the Cu catalyst with 1,3‐diketone 1a to form the enol‐[Cu] complex A (Scheme ). Oxidative reaction of the complex A with iodine by DMSO affords the 2‐iodo‐substituted 1,3‐diketone‐[Cu] complex intermediate B , followed by replacement of the intermediate B with DMSO to deliver the intermediate C . Decomposition of the intermediate C produces the 1,2,3‐triketone‐[Cu] complex intermediate D , which would sequentially undergo intramolecular C‐C bond cleavage to generate the carbonyl cation intermediate E .…”

Preparation of 3‐Alkylidenephthalides: Recent Advances

“…Gogoi et al described recently a novel Pd(II)-catalyzed decarbonylative alkyne insertion reaction (Scheme 42). [49] The proposed mechanism proceeds via CÀ H/CÀ C activation, alkyne insertion, intramolecular cyclization, and decarbonyla-tion, affording good yields of alkylidene phthalides (Scheme 43).…”

C—H Activation, a New Strategy for Synthesis of 3-Substituted Phthalides

“…Almost in the same time, Gogoi et al [11] reported a novel decarbonylative alkyne insertion reaction to synthesize sixmembered compounds with Pd(II) as the catalyst (Scheme 7). According to the proposed mechanism, the cyclization reaction of hydroxynaphthoquinones and disubstituted alkynes was carried out through C-H/C-C activation, acetylene insertion,…”