Self-Condensation of Enaminodiones as a Method for Benzene Ring Construction: Synthesis of Diacyl-Substituted Phenols and Catechols

Abstract

A novel transition metal-free approach for the construction of the benzene core has been developed through self-condensation of available enaminodiones. Functionalized acyl-substituted phenols and catechols were obtained in 29− 97% yields with high chemoselectivity under mild conditions. This base-promoted formal [4+2] annulation proceeds via cyclohexanone formation and involves the cascade transformation based on double Michael addition and aromatization (retro-Claisen cleavage and amine elimination).

Synthesis of Highly Substituted Biaryls by the Construction of a Benzene Ring via In Situ Formed Acetals

“…The requirement of expensive rare-earth element-based catalysts, issues with substituent placements and their influence in the success of the reactions, and the need for a high temperature are definite concern in these methods. The construction of benzene rings from acyclic or cyclic precursors has attracted the synthetic community for quite some time as it offers better prospects for placing multiple substituents . In this regard, the synthesis of biaryls via the construction of a benzene ring has been pursued by different groups in the recent years …”

Aniline assisted dimerization of phenylalanines: convenient synthesis of 2-aroyl-3-arylquinoline in an I2-DMSO system

“…In addition, acyl group elimination during the formation of an aromatic ring is a known process. 13,15 We did not detect the debenzylated by-product, showing good stability of the product under our conditions (Scheme 4f).…”

Copper(II)-Catalyzed [2+2+2] Annulation of Enaminones with Maleimides by a Traceless Directing Group Strategy

“…It could undergo various functionalization reactions and tandem reactions. [4] As a extremely efficient synthon, enaminone has a wide range of applications to build a heterocyclic skeleton [5] or benzene ring [6][7][8][9] in organic synthetic chemistry. Wan's group [6] and Dong's group [7] reported the acid-promoted [2+2+2] trimerization ofN,N -disubstituted enaminone via C-N bond cleavage to build benzene ring.…”

“…Wan and co-workers [8] realized the acid-promoted formal [4+2] cycloaddition for the synthesis of benzaldehyde by means of N,N -disubstituted enaminone and dienals. In 2019, Sosnovskikh et al [9] developed a method for the construction of the benzene core through self-condensation of available enaminodiones.…”