Regioselective addition of Grignard reagents to new lipophilic isoquinolinium salts applied to the synthesis of stable ethyl 1,2-disubstituted 1,2-dihydroisoquinoline-3-carboxylates and derivatives

New and stable ethyl 1,2-disubstituted 1,2-dihydroisoquinoline-3-carboxylates 6 and 12a were synthesized in good yields by regioselective addition reactions of alkyl Grignard reagents to lipophilic and soluble isoquinolinium salts 4 and 11. The salts 4 and 11 were obtained quantitatively and directly from isoquinoline-3carboxylates 1(a,b) with the corresponding alkyl halides 2 or symmetric alkyl dihalides 7 using solventless quaternization reaction conditions and were converted into the corresponding isoquinolinium perfuorobutanesulfonates 4 and 11a by ionic metathesis.