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

Abstract

Asymmetric Pd II -catalyzed intramolecular aminotrifluoromethoxylation of unactivated alkenes using readily accessible and stable CsOCF 3 as at rifluoromethoxide source has been developed, which affords aw ide variety of enantiomerically enriched b-substituted OCF 3 -containing piperidines in good yields.I ntroducing as terically bulky group into pyridine-oxazoline (Pyox) ligands is crucial to increasing both reactivity and enantioselectivity for the reaction. Additionally, the reaction features good functional group compatibility and mild reaction conditions. Scheme 1. Catalytic asymmetric trifluoromethoxylation.

Efficient Synthesis of Bulky 2,2’‐Bipyridine and (S)‐Pyridine‐Oxazoline Ligands

“…We desired to prepare a series of tetra‐arylated ligands with different steric parameters. Six aryl bromides, therefore, were chosen (Table 2, 2 b – 2 g) bearing one or two methyl or tert ‐butyl groups, as aryl groups with methyl [8b] and tert ‐butyl [4g,15] substituents are often incorporated in ligands for enhanced reactivity. The corresponding products ( 3 ab – 3 ag ) were obtained in good to excellent yields (86–93%).…”

“…While many transformations have been introduced with commercially available bidentate 2,2’‐bipyridine derivatives (bpy), the use of bulky NN’ ‐bidentate ligands [4] has been gaining attention. For example, bulky N , N ’‐bidentate ligands derived from 2,2′‐bipyridine and enantioenriched pyridine‐oxazolines have been used in metal‐catalyzed carbon dioxide reduction [4c,d] (Scheme 1a), enantioselective alkene difunctionalization reactions [4e–g,i] (Scheme 1b) and enantioselective electrochemical homocoupling reactions [4h] (Scheme 1c) with enhanced catalytic activity. In these reactions, the bulky ligands were implemented to prevent undesirable catalyst dimerization [4c,5] or to increase the metal center's electrophilicity toward binding olefin substrates [4f] .…”

Nucleophilic trifluoromethoxylation of alkyl halides without silver

“…For example, tris (dimethylamino)sulfonium trifluoromethoxide (TASOCF 3 ) was used as a trifluoromethoxylation reagent by Ritter's group to achieve the direct trifluoromethoxylation of aryl stannanes and aryl boronic acids with equivalent silver 25 . Liu group reported a palladium-catalyzed intramolecular aminotrifluoromethoxylation of alkenes with AgOCF 3 or CsOCF 3 as the trifluoromethoxylation reagent 26,27 . The catalytic C(sp 2 )-H trifluoromethoxylation of arenes with the new N-OCF 3 reagents under photocatalytic conditions had been reported by Ngai and Togni, respectively [28][29][30] .…”

Enantioselective Benzylation and Allylation of α-Trifluoromethoxy Indanones under Phase-Transfer Catalysis

“…We developed a strategy for the synthesis of chiral, non-racemic α-OCF 3 -ketones with a tetrasubstituted carbon center via a Pd-catalyzed enantioselective Tsuji-allylation reaction with high enantioselectivity (Scheme 1c) [45,46]. Very recently, Liu and co-workers reported the Pd-catalyzed enantioselective intramolecular trifluoromethoxylation reaction of alkenes using CsOCF 3 to furnish OCF 3 -compounds with a chiral stereogenic center (Scheme 1d) [47]. While these methods have broad substrate scopes with high enantioselectivity, all the methods require transition metal catalysts.…”