Reduction of quinolines to 1,2,3,4-tetrahydro derivatives employing a combination of NaCNBH<SUB>3</SUB> and BF<SUB>3</SUB>·OEt<SUB>2</SUB>

A regiospecific reduction of quinolines (and 1,10-phenanthroline) into the corresponding 1,2,3,4-tetrahydro derivatives using a combination of sodium cyanoborohydride and boron trifluoride etherate in refluxing methanol is described. Under the same conditions indole and acridine reduced to the corresponding dihydroderivatives, whereas acyl group transfer from oxygen to nitrogen atom is also noticed in the case of 8-acyloxyquinolines