Stereocontrolled Synthesis of (E)‐β,γ‐Unsaturated Esters via Palladium‐Catalyzed Cross‐Coupling of (E)‐Alkenylboronic Acids with α ‐Bromoacetic Esters

Abstract

The cross-coupling reaction of trans-alkenylboronic acids with α-bromoacetic esters was firstly studied. It was found that using Pd(OAc) 2 as catalyst, a bulky electron-rich phospine, (2-dicyclohexylphospino-biphenyl) as ligand, the reaction can be readily accomplished to give specific (E)-β,γ-unsaturated esters in high yields.

Palladium-Catalyzed Alkynylation of Secondary α-Bromo Carbonyl Compounds via Stille Coupling

“…alkenylmetals, 3,4 and alkylmetals 5,6 have recently been reported, few cases of cross-coupling reactions of alkynylmetals have been reported. 7,8 This is likely due to the sensitivity of the product β,γ-alkynyl carbonyls toward isomerization to conjugated species, processes which have been exploited in their own right.…”

“…Although numerous transition-metal-catalyzed cross-coupling reactions of α-halo carbonyl compounds with arylmetals, , alkenylmetals, , and alkylmetals , have recently been reported, few cases of cross-coupling reactions of alkynylmetals have been reported. , This is likely due to the sensitivity of the product β,γ-alkynyl carbonyls toward isomerization to conjugated species, processes which have been exploited in their own right. − Fu has developed a robust method for the synthesis of achiral 3-alkynoates not involving cross-coupling, while Lei and co-workers demonstrated a coupling reaction between primary α-halo carbonyl compounds and an alkynylstannane. However, secondary α-halo carbonyl compounds have remained elusive as starting materials.…”