Niobium Pentachloride Promoted Conversion of Carboxylic Acids to Carboxamides: Synthesis of the 4-Aryl-1,2,3,4-tetrahydroisoquinoline Alkaloid Structures - Nery, Marcelo S; Ribeiro, Renata P; Lopes, Claudio C; Lopes, Rosangela S C (Synthesis, 2003)