Addition of novel benzylmagnesium "ate" complexes of BnR2MgLi type to 2-(thio)pyridones and related compounds

Abstract Novel benzylation reagents BnR 2 MgLi were obtained by mixing benzylmagnesium chloride (BnMgCl) and appropriate organolithium compounds (RLi). As BnR 2 MgLi complexes are more nucleophilic than the parent Grignard compound they enabled regioselective C6-addition to electrophilic N-substituted 2-(thio)-pyridones and C4-addition to poorly reactive NH 2-(thio)pyridones in high and good yields, respectively. Thus, the application of these new reagents in efficient synthesis of 6-benzyl-3,6-dihydro- and 4-benzyl-3,4-dihydropyridin-2(1 H )-ones is described. The prospect of wider application of BnR 2 MgLi in 1,4-addition to other electrophiles, comprising six-membered α,β-unsaturated systems is also presented.