Access to Substituted Propenoic Acids via Rh(III)-Catalyzed C–H Allylation of (Hetero)Arenes with Methyleneoxetanones

Abstract

An efficient synthesis of disubstituted acrylic acids has been realized via Rh(III)-catalyzed C-H activation of (hetero)arenes and coupling with four-membered methyleneoxetanones under redox-neutral conditions. In most cases, the reactions are silver-free, and the products are exclusively E-selective with a broad substrate scope. The transformation proceeds via ortho C-H activation followed by selective olefin insertion and β-oxygen elimination.

A comprehensive overview of directing groups applied in metal-catalysed C–H functionalisation chemistry

“…Li reported the use of both 4- and 6-membered rings as allylic precursors in Rh-catalysed reactions ( Scheme 140A and B ). 824 , 825 While in the first case the driving force is the opening of the strained 4-membered lactone, the release of CO 2 facilitates the opening of the 6-membered ring. Importantly, both reactions proved to be selective for the E isomer.…”

Rh(III)‐catalyzed C6‐selective Acylmethylation and Carboxymethylation of 2‐Pyridones with Diazo Compounds

“…For instance, direct C6‐alkylation of 2‐pyridones with alkenes at the C6 position under Ni/Al cooperative catalysis were reported by the groups of Nakao [8a,b] and Cramer [8c,k] . Notably, introducing an easily attachable and detachable pyridine‐based directing group on the nitrogen atom of the 2‐pyridone skeleton enabled efficient C6−H alkylation of 2‐pyridones with diazomalonates, [8d] alkyl trifluoroborates, [8e] 3‐bromo‐2,2‐difluoropropene, [8f] alkenes, [8g,l] methyleneoxetanones, [8h] allenes, [8i] α‐carbonyl sulfoxonium ylides, [8j] 2‐carboxyl allylic alcohols, [8k] both enones and aldehydes [8m] and alkyl carboxylic acids [8n] in the presence of Ni(0), Mn(II), Rh(III), Co (III) or Rh(I) catalysts. Despite these advancements, new methods with improved catalytic efficiency, substrate scope and functional group tolerance are still in high demand.…”

Transition metal-catalyzed coupling of heterocyclic alkenesviaC–H functionalization: recent trends and applications

“…Li and co-workers showed the redoxneutral allylation of arenes (Scheme 137). 199 This silver-free protocol is compatible with a wide range of substrates. The procedure is extended to 2-pyridone and isoquinolone.…”