Sulfone-mediated synthesis of polysubstituted pyridines

Base-mediated and/or palladium(0)-catalysed bis(allylation) of alkyl 2-(tolylsulfonyl)acetates gives 1,6-dienes, which upon ozonolytic cleavage of the double bonds and ammonolysis give 2,6-disubstituted pyridine-4-carboxylic esters. Decarboxylation of one of the 1,6-diene intermediates followed by deprotonation–alkylation and ozonolysis–ammonolysis gives a 2,4,6-trisubstituted pyridine.