Silicon-assisted ethoxycarbonylmethylation of N-methylquinolinium and isoquinolinium iodides

A new regioselective route to 2-ethoxycarbonylmethyl- 1,2-dihydro-N-methylq uinolines and 1-ethoxycarbonylmethyl-1,2-dihydro-N-methylisoquinolines is d escribed starting from methylquinolinium or -isoquinolinium iodides and com mercially available ethyltrimethylsilyl acetate (ETSA). The methylene carba nion was generated by fluorodesilylation using caesium fluoride. On exposur e to air, the ethoxycarbonylmethyl adducts were oxidised, leading to the co rresponding alkylidene derivatives 4 and 5, whereas 2a in solution led slow ly to its regioisomer 6a.