Chiral Carboxylic Acid Enabled Achiral Rhodium(III)‐Catalyzed Enantioselective C−H Functionalization

Abstract

Reported is an achiral Cp Rh /chiral carboxylic acid catalyzed asymmetric C-H alkylation of diarylmethanamines with a diazomalonate, followed by cyclization and decarboxylation to afford 1,4-dihydroisoquinolin-3(2H)-one. Secondary alkylamines as well as nonprotected primary alkylamines underwent the transformation with high enantioselectivities (up to 98.5:1.5 e.r.) by using a newly developed chiral carboxylic acid as the sole source of chirality to achieve enantioselective C-H cleavage by a concerted metalation-deprotonation mechanism.

Cp*CoIII/Chiral Carboxylic Acid‐Catalyzed Enantioselective 1,4‐Addition Reactions of Indoles to Maleimides

“…Using a CCA with a sterically less hindered methoxy group at the 2′ position ( 4 b ), as well as one carrying a 2‐naphthyl group ( 4 c ) at the same location, resulted in decreased selectivity (entries 2 and 3). Unfortunately, the introduction of a substituent at the ortho ‐position of the carboxylic acid moiety ( 4 d ) decreased both the yield and enantioselectivity (entry 4), although a similar modification was effective in our previous work . Dicarboxylic acid 4 e and two CCAs with non‐binaphthyl backbones ( 4 f , 4 g ) that were used in previously reported Cp*Co(III)/CCA‐catalyzed enantioselective C−H functionalization reactions did not afford better results than 4 a (entries 5–7).…”

Introducing the Chiral Transient Directing Group Strategy to Rhodium(III)‐Catalyzed Asymmetric C−H Activation

“…Therefore, it is highly desirable to develop both new chiral catalysts ystems and new transformationst oe nrich the chemistry of the chiral TDG strategy.It is well knownt hat CpRh III -catalyzed CÀHa ctivation has achieved great success, [9] in which Cp is ac yclopentadienyl ligand. Notably,t he asymmetric CpRh III -catalyzed CÀHa ctivation has also been realized by variouss trategies, including designinga rtificial metalloenzyme, [10] employing chiral Cp ligands, [11] combining achiral CpRh III catalyst with an external chirala nion [12] or acid, [13] and using chirals ubstrate. [14] But to the best of our knowledge,a symmetricC pRh III -catalyzed CÀH activation by the chiral TDG strategy is still unknown.…”

Enantioselective C(sp3)–H Amidation of Thioamides Catalyzed by a CobaltIII/Chiral Carboxylic Acid Hybrid System

“…Zuschriften reactivity and selectivity (Scheme 2b). [26] Next, the scope with respect to dioxazolones 2 was examined using thioamides 1a and 1h.B oth electron-withdrawing and electron-donating groups on 2 were well tolerated to afford 63-90 %yields and 91:9-94:6 er (entries [12][13][14][15]. Even as terically hindered dioxazolone worked efficiently as the amidation reagent (entry 15).…”

“…[7][8][9][10][11] We recently demonstrated that an achiral Cp x Rh III catalyst hybridized with an external chiral source realizes enantioselective CÀHf unctionalization reactions (Scheme 1b). [13] These previous studies on group 9m etals, however, only focused on enantioselective C(sp 2 )ÀHf unctionalization reactions,a nd the more challenging C(sp 3 ) À H functionalization reactions remain unexplored. [10c, 14] Furthermore,C p x Co III catalysts have been less investigated for enantioselective reactions despite their ready availability and unique properties.…”