Catalytic Oxidative Trifluoromethoxylation of Allylic C−H Bonds Using a Palladium Catalyst

Abstract

A catalytic intermolecular allylic C-H trifluoromethoxylation reaction of alkenes has been developed based on the use of a palladium catalyst, CsOCF as the trifluoromethoxide source, and benzoquinone as the oxidant. This reaction provides an efficient route for directly accessing allylic trifluoromethoxy derivatives with excellent regioselectivities from terminal alkenes via an allylic C-H bond activation process.

Recent Advances and Perspectives of Transition Metal‐Catalyzed Asymmetric Fluorination Reactions

“…Recently, Liu and coworkers developed two novel palladium-catalyzed trifluoromethoxylation reactions of alkenes, generating the C -OCF 3 bond either by reductive elimination of high-valent RPd IV (OCF 3 ) intermediates [43] or by nucleophilic attack of a trifluoromethoxy anion at the allylic-Pd(II)X species (Scheme 13). [44] Thus, introducing a suitable chiral ligand into the palladium catalysts might realize the asymmetric trifluoromethoxylation reactions. [45] In addition, Wang and coworkers recently reported a novel enantioselective transition metal-catalyzed [2,3]sigmatropic rearrangement reaction of sulfonium ylides forming a sp 3 C-SCF 3 bond (Scheme 14), [46] which provides a highly efficient method for the synthesis of chiral trifluoromethylthiolated compounds.…”

Palladium(II)‐Catalyzed Enantioselective Aminotrifluoromethoxylation of Unactivated Alkenes using CsOCF3 as a Trifluoromethoxide Source

“…[13a] However,c ommonly-used nitrogen-containing ligands,s uch as bipyridines, phenanthrolines and bioxazolines,h ave ad etrimental effect on the reactivity of the palladium catalysts.T herefore, designing novel chiral ligands that can accelerate the reaction is essential for accomplishing an asymmetric version. Herein, we communicate am odified Pyox ligand bearing as terically bulky ortho-substituted group,which can remarkably enhance reaction efficiency and enantioselectivity.A dditionally,t he use of the more stable and easily prepared CsOCF 3 reagent derived from inexpensive trifluoromethanesulfonic acid (TfOH), [14] instead of AgOCF 3 ,i sc rucial to the asymmetric aminotrifluoromethoxylation reaction (Scheme 1b).…”

Palladium(II)‐Catalyzed Enantioselective Aminotrifluoromethoxylation of Unactivated Alkenes using CsOCF3 as a Trifluoromethoxide Source

“…[13] For instance,P d II -catalyzed intramolecular aminotrifluoromethoxylation of unactivated alkenes has been developed, in which the alkyl CÀOCF 3 bond was generated from CF 3 O-Pd IV Rs pecies by reductive elimination. Herein, we communicate am odified Pyox ligand bearing as terically bulky ortho-substituted group,which can remarkably enhance reaction efficiency and enantioselectivity.A dditionally,t he use of the more stable and easily prepared CsOCF 3 reagent derived from inexpensive trifluoromethanesulfonic acid (TfOH), [14] instead of AgOCF 3 ,i sc rucial to the asymmetric aminotrifluoromethoxylation reaction (Scheme 1b). Herein, we communicate am odified Pyox ligand bearing as terically bulky ortho-substituted group,which can remarkably enhance reaction efficiency and enantioselectivity.A dditionally,t he use of the more stable and easily prepared CsOCF 3 reagent derived from inexpensive trifluoromethanesulfonic acid (TfOH), [14] instead of AgOCF 3 ,i sc rucial to the asymmetric aminotrifluoromethoxylation reaction (Scheme 1b).…”