Abdalla Mohamed Negm

REACTIONS WITH 6-METHYL-2-THIOURACIL SYNTHESIS OF DIPYRIMIDINO[2,1-b:1′,2′-c]THIAZINE. A NEW RING SYSTEM

Abstract Bromination of 6-methyl-2-thiouracil (I) gave the 5-bromo analogue II. Alkylation of each of I and II yielded the S-alkyl derivatives IIIa-g. Cyclisation of IIIa,c gave the 3,7-dimethylthiazolo[3,2-a]pyrimidines VIIa,b. The 2-arylmethylenethiazolo[3,2-a]pyrimidines VIa-i were synthesized via the reaction of either I or II with a mixture of chloroacetic acid and aromatic aldehydes. The 2-methylthiopyrimidine analogue VIII reacted with aromatic amines to produce the 2-arylamino derivatives IXa,b. Condensation of the 2-hydrazino analogue X with aromatic aldehydes formed the Schiffs bases XIa-e. The analogue XIb could be cyclised by bromine into the 6-bromo-s-triazolo[4,3-a]pyrimidine derivative XIII. The reaction of X with each of carbon disulphide and chloroacetyl chloride gave the s-triazolo[4,3-a]pyrimidine XVII and pyrimido[2,1-c]-as-triazine XIX derivatives, respectively. Also, compound X reacted with either 2,4-pentanedione, 3-chloro-2,4-pentanedione or 1,1,1-trifluoro-2,4-pentanedione to for...

STUDIES WITH POLYFUNCTIONALLY SUBSTITUTED HETEROAROMATICS: NEW ROUTES FOR SYNTHESIS OF BENZOAZINES

Abstract Pyridazine (I) reacts with dimethyl acetylenedicarboxylate and with N-phenyl-maleimide yielding phthalazine (II) and pyrrolophthalazine (III), respectively. Pyridine IV reacts with benzylidene malononitrile to give compound VI. Compounds VIa–c could be successfully converted into the isoquinolines XIa–c on treatment with acrylonitrile. In contrast to the behavior of arylidene malononitrile, compound IV react with N-phenylmaleimide to yield the pyrroloisoquinoline XIII. Similarly, the reaction of compound IV with each of tetracyanoethylene and dimethyl acetylenedicarboxylate gave compounds XIV and XV respectively.

Pyrimidine Derivatives and Related Compounds, IX / Preparation of 5-Aminopyrazolo[1,5-a]pyrimidines and of Oxazino[4,5 : 5,6]pyrazolo[1,5-a]pyrimidines, a New Ring System

Whereas the 5-aminopyrazole derivatives (1 a, b) react with ethyl β-amino-β-trichloro-methylmethylenecyanoacetate (2) in basic media to yield the corresponding 5-aminopyrazolo[1,5-a]pyrimidine derivatives (3a, b), the reaction of la, b with 2 in refluxing acetic acid has afforded oxazino[4,5:5,6]pyrazolo[1,5-a]pyrimidine derivatives. 5-Amino-3-phenyl-4-phenylazopyrazole (12) reacted with 2 in refluxing pyridine to yield the 5-amino-2-phenyl-3-phenylazopyrazolo[1,5-a]pyrimidine derivative (18). On the other hand, the reaction of 12 and 2 in refluxing acetic acid has afforded a mixture of the oxazino[4,5:5′,6′]pyrazolo[1,5-a]pyrimidine derivatives (14) and the pyrazolo[3,4-d]-astriazine derivatives (15). The mechanism of the formation of reaction products is discussed.

Heterocyclic synthesis with nitriles: new routes for synthesis of pyridazines, pyridines and their fused derivatives.

Phenylazocyanothioacetamide1 reacts with malononitrile to afford the pyridinethione4 which reacts with phenacylbromide to yield the pyridine-S-phenacyl derivative6. 1 reacts with ethyl cyanoacetate to yield the pyridazine derivative,8, and with phenacyl bromide to afford the N-phenacyl derivative11, instead of the thiazole10. Compound11 afforded the pyrazolopyridine13 on reaction with malononitrile while10 was obtained on coupling of the thiazole14 with diazotised aniline. Compound10 reacts with malononitrile to afford the thiazolyl pyridazine15. Compound1 reacts with malononitrile dimer to afford the pyridopyridazine derivative17a. 1 reacts also with active methylene heterocycles to afford the pyrazolo and thiazolo-fused pyridazines20 and23, respectively.