New synthesis of 2,4-diamino-10-(4-bromo-phenylamino)-10H-9-oxa-1-aza-anthracene-3-carbonitrile, 2,4- diamino-10-p-tolylamino-10H-9-oxa-1-anthracec-3-carbonitrile and 2-(2-amino-3-cyano-4H-chromen-4-yl)- malononitrile