Reaction of 4-Aryl-2-aminobuta-1,3-diene-1,1,3-tricarbonitriles with CH-Nucleophiles. Part 1. Synthesis of 5-Aryl-2,4-diamino-8,8-dimethyl-6-oxo-6,7,8,9-tetrahydro-5H-chromeno [2,3-b]pyridine-3-carbonitriles (III).