Expedient One-Pot Synthesis of Novel Chiral 2-Substituted 5-Phenyl-1,4-benzodiazepine Scaffolds from Amino Acid-Derived Amino Nitriles

An efficient and stereocontrolled synthesis of phenylalanine- and tryptophan-derived 5-phenyl-1,4-benzodiazepines is described. This new methodology involves, as a key step, the synthesis of 5-phenyl-2,3-dihydro-1H-1,4-benzodiazepines by a one-pot cyano reduction and reductive cyclization of the appropriate amino nitrile, which were obtained via a modified Strecker reaction of N-protected alpha-amino aldehydes with 2-aminobenzophenone and trimethylsilyl cyanide. The subsequent reduction of these 2,3-dihydro-1H-1,4-benzodiazepines, followed by regioselective alkylation or acylation at position 4, led to 2,4-disubstituted-5-phenyl-2,3,4,5-tetrahydro-1H-1,4-benzodiazepine.