Palladium-catalysed regio- and stereoselective arylative substitution of γ,δ-epoxy-α,β-unsaturated esters and amides by sodium tetraaryl borates
作者:Yasemin Bilgi、Melih Kuş、Levent Artok
DOI:10.1039/d0ob01226b
日期:——
Palladium-catalysed reactions of γ,δ-epoxy-α,β-unsaturated esters and amides with NaBAr4 reagents proceeded regio- and stereoselectively, producing allylic homoallyl alcohols with aryl-substituents in the allylic position for a wide range of substrates. AsPh3 was found to be a competent ligand for the arylation reaction, whereas phosphine ligand/Lewis acidic organoboron combinations favoured the substitution
Palladium-catalyzed stereospecific epoxide-opening reaction of γ,δ-epoxy-α,β-unsaturated esters with an alkylboronic acid leading to γ,δ-vicinal diols with double inversion of the configuration
A palladium-catalyzed stereospecific epoxide-opening reaction of gamma,delta-epoxy-alpha,beta-unsaturated esters with an alkylboronic acid leading to gamma,delta-vicinal diols is described, which proceeds with retention of the configuration, i.e., via two consecutive S(N)2 processes, to afford the corresponding gamma,delta-cyclic boronates in high yields.
The unprecedented, stereospecific interconversion of cis- and trans-gamma,delta-epoxy alpha,beta-unsaturated ester systems has been realized, which involves the palladium-catalyzed stereospecific alkoxy or hydroxy substitution reaction with double inversion of configuration at the gamma-position as the key step. The new methodology is not only applicable to various disubstituted and trisubstituted epoxy unsaturated esters, but also these interconversions proceed with an extremely high degree of stereoselectivity and efficiency. (C) 2008 Elsevier Ltd. All rights reserved.