The reaction ofN,N-dimethyldichloromethyleniminium chloride (phosgeniminium chloride) with 6-N-arylaminouracils. A new and convenient “one pot” synthesis of l,3-dimethyl-5- dimethylaminopyrimido[4,5-b]quinoline-(1H,3H)-2,4-diones, 1,3-dimethyl-5-chloropyrimido[4,5-b]quinoline-(1H,3H)-2,4-diones and 3-methyl-10-alkyl-5-chloropyrimido[4,5-b]quinoline-(3H,10H)-2,4-diones (3-methyl-10-alkyl-5-chloro-5-deazaflavins)