An Efficient Synthesis of Substituted Quinolines

The addition of substituted anilines to ”vinamidinium" bis-tetrafluoroborate salt 1 [2-dimethylaminomethylene-1,3-bis(dimethylimmonio)propane bis-tetrafluoroborate], followed by cyclization of the resulting imino-eneamine salt and hydrolysis of the masked aldehydes 2, provide the corresponding 3-formyl quinolines 3. While the condensation of both 1 and its analogous bis-perchlorate salt and amidines are known to provide pyrimidines, we believe this is the first example of a quinoline annulation sequence with ”vinamidinium" bis-tetrafluoroborate salt 1 and anilines.