Direct Stereoconvergent Allylation of Chiral Alkylcopper Nucleophiles with Racemic Allylic Phosphates

Abstract

Copper‐catalyzed stereoconvergent allylation of chiral sp3‐hybridized carbon nucleophiles with a racemic mixture of acyclic secondary allylic phosphates is reported. In the presence of a copper‐catalyst complexed with chiral BenzP* ligand, tandem coupling reaction of vinyl arenes, bis(pinacolato)diboron, and racemic allylic phosphates provided β‐chiral alkylboronates possessing (E)‐alkenyl moiety through a direct stereoconvergent allylic coupling with concomitant generation of a C(sp3)‐stereogenic center. A range of vinyl (hetero)arenes and secondary allylic phosphates bearing 1°, 2°, 3° alkyl and phenyl α‐substituents were suitable for the reaction, forming products with high enantioselectivities up to 95 % ee. Density functional theory calculations were conducted in detail to elucidate the origin of the observed regioselectivity of borylcupration and stereoconvergent (E)‐olefin formation from racemic allylic phosphates.

Copper-Catalyzed Enantiotopic-Group-Selective Allylation of gem-Diborylalkanes

“…Furthermore, using 7 and 2c as substrates also gave the products 8 and 9 with ratios of 3:1 (Scheme b) with good optical purity. These experimental results suggested that both S N 2′ and S N 2-like processes could be involved at the C–C bond formation event by the attack of the chiral α-borylalkyl-copper species C to the 3- or 1-position of the allyl bromide …”

Copper-Catalyzed Borylative Difunctionalization of π-Systems

“…However, asymmetric borylcuprations initially generating a stereocenter have also been demonstrated, with the first report by the Yun group (Scheme , 102a , 102b ) . This strategy was recently extended to racemic allylic phosphates leading to 1,2-disubstituted alkenes ( 102c ) . The borylallylation was largely limited to styrenes, though some success was found with vinylsilanes.…”

“…9 The skipped diene products were generated in 86 This strategy was recently extended to racemic allylic phosphates leading to 1,2-disubstituted alkenes (102c). 87 The borylallylation was largely limited to styrenes, though some success was found with vinylsilanes. DFT studies revealed S N 2′ oxidative addition between the benzylic copper and allylic phosphate as the most likely reaction pathway.…”

Cooperative Cu/Pd-Catalyzed 1,5-Boroacylation of Cyclopropyl-Substituted Alkylidenecyclopropanes

“…These reactions were initiated by a borylcupration of alkene with Cu–Bpin species and terminated using an electrophilic reagent. Several groups including Brown, Hoveyda, Yun, and others have made significant contributions in this field.…”