Ammonium Acetate: An Efficient Reagent for the One-pot Synthesis of 5-Aryl-7,8,13,14-tetrahydrodibenzo[a,i] phenanthridines, 2,4-Diaryl-6,7-benzo-3-azabicyclo[3.3.1]nonan-9-ones and α,α'-Bis(substituted benzylidene)cycloalkanones