Palladium-Catalyzed Carboxylation of Allyl Stannanes and Carboxylative Coupling of Allyl Stannanes and Allyl Halides Abstract

摘要

The reaction of allyl stannanes with CO2 to form stannyl carboxylates (esters) is catalyzed by Pd(PR3)4 complexes. Thus, R3SnCH2CH=CH2 [R=Me and Ph]are converted to R3SnO2 CCH2CH=CH2 and R3SnO2CCH=CHCH3 under 33 atm of CO2 (70°C, THF) in moderate to excellent yield in the presence of 8 mol% Pd(PPh3)4 ; polycarboxylation of diallyldibutyltin and tetraallyltin also is effected, producing the respective di- and tetracarboxylates, Bu2Sn(O2CCH2CH=CH2)2 and Sn(O2CCH2 CH=CH2)4 , along with the corresponding isomeric crotyl derivatives. In the presence of allyl halides, allyl stannanes and CO2 undergo carboxylative coupling to produce allyl esters. Under these conditions other Sn-C (Sn-alkyl, -aryl, -vinyl) and Si-C (Si-allyl, -alkyl, -aryl, -vinyl) bonds are inert to carboxylation and carboxylative coupling with allyl halides. A tentative mechanism is proposed to account for this catalytic carboxylation of a main group metal-carbon bond.