Enantioconvergent Reductive C(sp)−C(sp³) Cross‐Coupling to Access Chiral α‐Alkynyl Phosphonates Under Dual Nickel/Photoredox Catalysis

Abstract

Transition-metal-catalyzed asymmetric carbonÀ carbon bond formation to forge phosphonates with an α-chiral carbon center through C(sp 3 )À C(sp 3 ) and C(sp 2 )À C(sp 3 ) couplings has been successful. However, the enantioselective C(sp)À C(sp 3 ) coupling has not yet been disclosed. Reported herein is an unprecedented enantioconvergent cross-coupling of alkynyl bromides and α-bromo phosphonates to deliver chiral α-alkynyl phosphonates.

Nickel/photoredox-catalyzed carbonylative transformations of α-phosphorus-, α-sulfur-, and α-boron-substituted alkyl halides

“…7), based on the above mechanistic studies and related literature. 20 First, blue light irradiation of the photoredox catalyst would generate the excited-state PC*, which will oxidize the NiI species via a SET process to generate Ni II species. Subsequently, the α-phosphonate alkyl radical A was delivered from α-bromophosphate through a SET reduction process.…”

Dual Nickel- and Photoredox-Catalyzed Asymmetric Reductive Cross-Couplings: Just a Change of the Reduction System?

“…The synthesis of related structures typically relies on noble metal catalysis and complicated chiral ligands, with strict requirements on substrate skeletons, which makes the development of an efficient, simple, and modular synthetic method highly rewarding . Through systematic condition optimizations, we ultimately achieved this transformation to deliver the products in good yields (Figure A) . Despite the occurrence of significant background reactions under ligand-free conditions, these products still exhibited good enantioselectivity under the dual Ni/photoredox-catalyzed RCC system (Figure B).…”

“…Subsequently, we outline various chiral carbon− carbon bond-forming types obtained by this dual Ni/photoredox catalysis system and their mechanisms. In terms of chiral C(sp 3 )− C(sp 2 ) bond formation, extensive discussion focuses on the asymmetric arylations of α-chloroboronates, α-trifluoromethyl alkyl bromides, α-bromophosphonates, and so on. In the realm of chiral C(sp 3 )−C(sp) bond formation, asymmetric alkynylations of αbromophosphonates and α-trifluoromethyl alkyl bromides have been presented herein.…”

“…In the realm of chiral C(sp 3 )−C(sp) bond formation, asymmetric alkynylations of αbromophosphonates and α-trifluoromethyl alkyl bromides have been presented herein. Regarding C(sp 3 )−C(sp 3 ) bond formation, we take the asymmetric alkylation of α-chloroboronates as a compelling example to illustrate the great efficiency of this dual catalysis system. This summary would enable a better grasp of the advantages of this dual catalysis system and clarify how the photocatalysis regime facilitates enantioselective transformations.…”

“…Ed . 2023 , 62 , e202218299 Lu, S.; Hu, Z.; Wang, D.; XU, T. Halogen-Atom Transfer Enabled Catalytic Enantioselective Coupling to Chiral Trifluoromethylated Alkynes via Dual Nickel and Photocatalysis.…”