4-Chloro-2,3-disubstituted-2-cyclobutenones

Chloro-2,3-disubstituted 2-cyclobutenones undergo a Pd-assisted cross-coupling reaction with 2-stannylated iiirans to give 4-hydroxybenzofurans <93JOC3SSO>. 

Tin Derivatives. A regiocontrolled method for construction of substituted benzofurans, dibenzofurans, benzothiophenes, and dibenzothiophenes uses 4-chloro-2,3-disubstituted-2-cyclobutenones as reactants together with a heterocycle (Scheme 17). In the construction... 

Pd(PhCN)2Cl2-catalyzed reaction of 4-chloro-2,3-disubstituted-2-cyclobutenones with aryl or 1-alkenylstannane reagents afforded substituted benzannulated heteroaromatics (eq 19). This process was designed to provide 4-vinylic- (or arylic- or heteroarylic-) cyclobutenones via a palladium catalyzed cross-coupling reaction. The cross-coupled products, in turn, would be transformed to substituted phenols upon thermolysis. 

Disubstituted 4-chloro-2-cyclobutenones 75 undergo the palladium-catalyzed cross-coupling reaction with vinyl- and arylstannanes 76 or vinylzir-conium reagents to give the 4-R sa,-2-cyclobutenones 77. Without isolation, these cyclobutenones 77 are rearranged to the substituted phenols 78 on thermolysis [38], Application of this method to the stannylated heteroaromatics 79 provides a synthetic route to the aromatic benzoheterocycles 80 [39]. (Scheme 27 and 28)... 

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