Synthesis of Polysubstituted Phenols by Rhodium‐Catalyzed C−H/Diazo Coupling and Tandem Annulation

Abstract

The rhodium(III)-catalyzed CÀ H/diazo coupling and tandem annulation of 3-oxopent-4enenitriles have been proposed for the synthesis of polysubstituted phenols. Most products of phenols are obtained in good yields. Several preliminary mechanistic studies and derivatization reactions of phenol products were also performed. This method offers an alternative approach for the synthesis of useful diverse phenols.

Transition‐Metal‐Catalyzed C−H Bond Functionalization of Arenes/Heteroarenes via Tandem C−H Activation and Subsequent Carbene Migratory Insertion Strategy

“…oxopent-4-enenitriles with α-diazocarbonyl compounds (Scheme 25c). [71] The methodology being the first example of its kind requires easily accessible and cost-effective substrates where the directing group acts as a part of the cyclization process, thereby generating tetra-and penta-substituted phenols in one step.…”

Rhodium‐Catalyzed Regioselective C—O and C—C Bonds Formation of 3‐Oxopent‐4‐enenitriles with Alkynes for the Synthesis of Polysubstituted 2H‐Pyrans

“…Based on the above mechanism research experiments and referring literatures, [14][15][16] a possible mechanism is thereby proposed (Scheme 4). At the beginning, the depolymerization product of [Cp*RhCl 2 ] 2 is likely to be treated by -OAc to generate the active catalyst Cp*Rh(OAc) 2 .…”

“…Previously, we developed 3‐oxopent‐4‐enenitriles and sequentially achieved their rhodium(III)‐catalyzed C—H bond activation and annulation with diazo compounds leading to polysubstituted phenols, which also underwent the C—C/C—C coupling pathway (Scheme 1a). [ 16 ] As a continuation of our ongoing exploration on metal catalyzed reactions and the construction of heterocycles, [ 17 ] and based on recent reports on chelation‐assisted alkenyl C—H functionalization, [ 18 ] we herein seek to investigate the reaction profile of 3‐oxopent‐4‐enenitriles with alkynes under rhodium catalysis. The experimental results showed that polysubstituted 2 H ‐pyran derivatives were displayed through regioselective C—O and C—C bonds formation originating from O—Rh bond coupling (Scheme 1b).…”

Water as an oxygen source in I2-mediated construction of highly functionalized maleimide-fused phenols

“…In addition, other methods mainly involve basic reactions, which include benzannulation, 8 Diels–Alder cycloaromatization, 9 cyclocondensation of enones with 1,3-dicabonyl compounds 10 and others. 11 Although great progress has been made in the synthesis of phenols, a number of notable limitations exist: introducing additional directing groups, requiring transition-metal catalysis, focusing on special functional substrates, or the synthesis of multi-substituted phenols being difficult, particularly heterocycle-fused phenols. Therefore, the development of efficient and straightforward strategies for functionalized phenol construction is still a desirable and challenging issue.…”