Facile synthesis of axially chiral styrene-type carboxylic acids via palladium-catalyzed asymmetric C–H activation

Abstract

Palladium-catalyzed asymmetric C–H functionalization to yield axially chiral styrene-type carboxylic acids is described, in which axial chirality and sterically hindered group were incorporated in one-step.

Development of Axially Chiral Styrene-Type Carboxylic Acid Ligands via Palladium-Catalyzed Asymmetric C–H Alkynylation

“…We recently reported a novel path for the construction of axially chiral styrene-type CCAs from cinnamic acid derivatives via palladium-catalyzed olefination or arylation of C(sp 2 )−H bonds, which introduced the axial chirality and the sterically hindered group in one step. 4 While such arylated or olefinated CCAs showed inefficiency in recognizing prochiral C−H bonds, further modification of cinnamic acids to construct diverse axially chiral ligands offered a solution to address this issue. Undoubtedly, palladium-catalyzed enantioslective C−H bond functionalization 5,6 represents the most facile and powerful strategy to make such axially chiral styrene-type carboxylic acids, but it still needs to be developed further.…”

“…Although many contributions to the development of new CCAs have been made, there is still limited diversity of the applied CCAs in comparison with that of chiral Cp* ligands. We recently reported a novel path for the construction of axially chiral styrene-type CCAs from cinnamic acid derivatives via palladium-catalyzed olefination or arylation of C­(sp 2 )–H bonds, which introduced the axial chirality and the sterically hindered group in one step . While such arylated or olefinated CCAs showed inefficiency in recognizing prochiral C–H bonds, further modification of cinnamic acids to construct diverse axially chiral ligands offered a solution to address this issue.…”

Pd(II)-Catalyzed C(alkenyl)–H Activation Facilitated by a Transient Directing Group

“…We thus questioned whether using an enantioenriched TDG could be used to develop an atroposelective version of this transformation (Figure 2). [25][26][27][28][29][30][31][32][33][34] In comparison to axially chiral styrenes, synthesis of atropoisomeric 1,3-dienes are less explored owing to synthetic difficulties and facile product racemization (Figure 2A). [35][36][37][38] In one study, a C2-symmetric cyclic 1,3-diene with large alkenyl substituents possessing a chiral axis along the C(alkenyl)-C(alkenyl) bond was synthesized, and the two atropoisomers were separated through chiral resolution.…”

Traditional and sustainable approaches for the construction of C–C bonds by harnessing C–H arylation

“…Very recently Wang and co-workers demonstrated synthesis of styrene-type chiral carboxylic acids (Fig. 4A, iv ) 62 . These types of chiral carboxylic acids are majorly used as chiral ligands in transition-metal catalysis or as organocatalysts, this clearly reveals the importance of this protocol.…”