Selective palladium-mediated carbon–oxygen bond and carbon-–sulfur bond forming reactions which involve functionalized Csp2-hybridized halides or triflates and Csp-hybridized halides

(E)- and (Z)-2,3-dibromopropenoates were found to be able to react with Bu(3)SnXR(1) (X = O,S: R(1) = alkyl, aryl) in NMP solution at 20 degrees C in the presence of Pd(PPh(3))(4) to give the corresponding 3-alkoxy, 3-arylthio and 3-alkylthio substituted products. Under similar conditions methyl (E)- and (Z)-3-bromopropenoate, methyl (Z)-3-iodo-2-octenoate, 3-alkoxycarbonyl Substituted (cyclo)alkenyl triflates as well as methyl 3-bromopropionate, were converted into the corresponding 3-methylthio or 3-phenylthio substituted products when compounds Bu(3)SnSR(1) (R(1) = Me. Ph) were used as nucleophiles. On the contrary. 2-bromo substituted alpha,beta-unsaturated esters or lactones as well as a 2-substituted alkyl 3-bromopropenoate did not undergo Pd-mediated substitution reactions by treatment with Bu(3)SnOR(1) and 3-substituted (E)-2,3-dibromopropenoates, and 3-substituted (Z)-3-iodopropenoates afforded the corresponding alpha,beta-acetylenic esters, when reacted with Bu(3)SnOR(1) in the presence of Pd(PPh(3))(4). A selective monosubstitution reaction also occurred when 1,2-dibromobenzene, was reacted with PhSSnBu(3) in toluene in the presence of Pd(PPh(3))(4). Finally. compounds (E)- and (Z)-22a, which were prepared by Pd-mediated C-S bond forming reactions, were used its direct precursors to some natural carboxyamides. Copyright (C) 1996 Elsevier Science Ltd