Stereoselective Cobalt-Catalyzed Cross-Coupling Reactions of Arylzinc Chlorides with α-Bromolactones and Related Derivatives

Abstract

α-Bromolactones bearing a substituent in the β-position undergo a highly trans-diastereoselective arylation with arylzinc chlorides in the presence of 10–20% CoCl2 and 10–20% PPh3 in THF under mild conditions (25 °C, 16 h) leading to optically enriched α-arylated lactones and protected aldol products (99% ee) in 52–96% yield. The synthetic utility of this arylation was demonstrated by the stereoselective preparation of an artificial rotenoid MOM-protected munduserol derivative.

Cobalt‐Catalyzed α‐Arylation of Substituted α‐Bromo α‐Fluoro β‐Lactams with Diaryl Zinc Reagents: Generalization to Functionalized Bromo Derivatives

“…Even an α‐bromo, α,α‐difluoroamide proved to be a suitable substrate as 9 ha was isolated in 81 % yield. Motivated by the robustness of the cross‐coupling conditions, α‐bromo lactones ( 8 a and 8 b ) were subjected to the developed cross‐coupling conditions, and 10 aa and 10 ab were obtained in 74 % and 85 % yield, respectively. Also, α‐bromo esters including an α‐bromo α‐fluoro and an α‐bromo α,α‐difluoro ester were suitable substrates ( 8 c – 8 e ) furnishing the cross‐coupled products 10 ca , 10 da and 10 ea in satisfying yields ranging from 53 % to 61 %.…”

Enantioselective Hydrofunctionalization of Cyclobutenones: Total Synthesis of gem‐Dimethylcyclobutane Natural Products

“…[15] However, the yield dropped significantly when more electron-rich arylzinc halide was used (Table S8). The cobalt catalytic system (CoCl 2 , PPh 3 ) [16] turned out to be the optimal choice, and an excellent substrate-controlled diastereoselectivity was observed as well. The reaction of p-MeOC 6 H 4 ZnCl•MgX 2 •LiX 5 b' with 4 a gave product 7 a in 63 % and 99 % ee (Table S9).…”

Preparation and reactions of polyfunctional magnesium and zinc organometallics in organic synthesis

“… 30 For example, highly diastereoselective cross-couplings were achieved with α-bromo lactones (see Scheme 9 ). 31 …”