Tayseer A. Abdallah

New Routes to Pyridino(2,3-d)pyrimidin-4-one and Pyridino- (2,3-d)triazolino(4,5-a)pyrimidin-5-one Derivatives

2-Thioxopyrimidinyl-5-(N,N-dimethylamino)formamidine (5) and 1,3-diphenyltriazolo[3,4-d]pyrimidinyl-N,N-dimethylformamidine (14) were prepared by condensation of 6-amino-2-thioxo-1,3-dihydropyrimidin-4-one (2) and 7-amino-1,3-diphenyl-1,2,4-triazolo[4,3-a]pyrimidin-4-one (13) with dimethylformamide dimethyl- acetal (DMFDMA). Compound 5 reacts with acetophenone and 2-acetylthiophene to give the 2-thioxo-1,3-dihydropyridino[2,3-d]pyrimidin-4-ones 3a and 3b, respectively. Compounds 3a,b react with hydrazonoyl halides 6,7 to give pyridino[2,3-d]triazolo[4,5-a]pyrimidin-4-ones 11a-d and not the isomeric structures 12a-d. Formamidines of type 14 react with ethyl cyanoacetate, malononitrile and benzoyl acetonitrile to give the 1,3-diphenyl-3a-hydropyridino[2,3-d]1,2,4-triazolo[4,5-a]pyrimidin-4-one derivatives 15a,b and 18, respectively. The structures of the newly synthesized compounds are established on the basis of chemical and spectroscopic evidences as well as their synthesis by alternative methods.

Novel synthesis of 1,2,4-triazolo[4,3-a]pyrimidin-5-one derivatives

Abstract 1,2-Dihydro-2-thioxopyrimidin-4(3H)ones 6 react with C-ethoxycarbonyl-N-arylhydrazonoyl chlorides 1 to give 1,2,4-triazolo[4,3-a]pyrimidines 11 in good yield. The latter products 11 react with benzenediazonium chloride, nitrous acid, acetyl chloride and chloroacetyl chloride to give the corresponding substitution products 16–18. The structures of the newly synthesized compounds are established on the basis of chemical and spectroscopic evidence.

A Novel Synthesis of 1,2,4-Triazolopteridines

Reaction of 1,2-dihydro-2-thioxopteridin-4(3H)-one, 6,7-dimethyl-1,2-dihydro-2-thioxopteridin-4(3H)-one and 6,7-diphenyl-1,2-dihydro-2-thioxopteridin- 4(3H)-one with hydrazonoyl halides affords the title compounds in good yields.

REACTIVITY OF 1-METHYLISOQUINOLINE. ONE POT SYNTHESIS OF BENZO[a]-QUINOLIZINE DERIVATIVES

ABSTRACT 1-Methylisoquinoline 1 reacts with arylidine malononitrile 2 in the presence of piperidine to give the corresponding Michael adducts pyridinoisoquinolines 5. The structures of the products 5 were established on the basis of elemental and spectral analyses and studies of their chemical behaviours.

Reactivity of 1-Methylisoquinoline. Synthesis of 2-(1-Isoquinolinemethylidene)-1,3,4-Thiadiazole Derivatives

1-methyl-3,4-dihydro-6,7-dimethoxyisoquinoline reacts with arylisothiocyanates to give the corresponding thioanilides 2 . Treatment of the latter compounds 2 with hydrazonoyl halides 3 and 10 leads to the formation of thiadiazoles 7 and 12 .

STUDIES ON ORGANOPHOSPHORUS COMPOUNDS VI1–5: Utility of Lawesson's Reagent for Synthesis of Thiaphosphorine, Thioxanthene, and Thiaphosphole Derivatives

Arylidene malonate derivatives 2a–c reacted with Lawessons reagent (1) LR in equimolar ratio to yield the oxathiaphosphorine derivatives 3a–c. The behaviour of LR towards cyclic ketones was also examined and yielded the thioxanthene derivatives 5a,b. On the other hand, arylidene pyrazolone 8 reacted with LR to give the phosphole 10. Aminobenzenethiophene 11 reacted with LR under reflux to produce the corresponding thiazaphosphorine 12.

Synthesis of Tetra- and Pentaheterocyclic Compounds Incorporated Isoquinoline Moiety

7-Amino-2,3-dimethoxy-9-phenyl-5,6,9,6a-tetrahydropyridino[2,1-a]-isoquinoline-8,10-dicarbonitrile 5 was prepared via Michael addition reaction of benzylidenemalononitrile 2 with isoquinoline-1-carbonitrile 1. Reaction of 5 with triethyl orthoformate and formamide led to the formation of the corresponding 4-ethoxymethylene and 4-aminopyrimidine derivatives of benzo[a]quinolizines 6 and 7, respectively. Compound 6 reacted with hydrazine to give imino-amino compound 8. The latter compound reacted with formic acid, triethyl orthoformate, acetic anhydride or benzoyl chloride to give the triazolopyrimidine derivatives 9, 10 and 11, respectively. Compound 8 reacted with hydrazonoyl halides 12, 13 and diethyl oxalate to give triazinopyrimidine and triazolopyrimidine derivatives 16, 17 and 20, respectively.

REACTIVITY OF ETHYL 1,2,3,4-TETRAHYDRO-6,7-DIMETHOXY-1-ISOQUINOLYLIDENE ACETATE TOWARDS NITRILIMINES. SYNTHESIS OF PYRROLO[2,1-a]-5,6-DIHYDROISOQUINOLINE

ABSTRACT Hydrazonoyl halides 3 and 8 react with 3,4-dihydro-6,7-dimethoxyisoquinoline-1-methyleneethoxycarbonyl 2 to give ethyl 2-(1,2,3,4-tetrahydro-6,7-dimethoxyisoquinoline-1-ylidene)-2-(N-phenyl-N′-benzylidene-hydrazine) acetate 7 and pyrrolo[2,1-a]5,6-dihydroisoquinoline 13 respectively. Structures of the new compounds were elucidated on the basis of elemental analysis, spectral data (IR, 1H NMR, MS).

A facile access for synthesis of novel isoquinoline-based heterocycles

Hydrazonoyl halides 2, 7 and 12 react with alkyl 2-(3,4-dihydro-6,7-dimethoxy-2H-isoquinoline-1-ylidene)carboxylate 1 to give 4-(3,4-dihydro-6,7-dimethoxy-2H-isoquinoline-1-ylidene)-2,5-diaryl-2,4-dihydropyrazol-3-one 6, alkyl 2-arylazo-5,6-dihydro-8,9-dimethoxy-3-alkyl(or aryl)pyrrolo[2,1-α]isoquinoline-1-carboxylate 10 and alkyl 2-(2-arylhydrazono)-2,3,5,6-tetrahydro-8,9-dimethoxy-3-oxopyrrolo[2,1-α]isoquinoline-1-carboxylate 15, respectively. The structures of the new compounds were elucidated on the basis of elemental analyses, spectral data and X-ray crystallographic analyses.

Studies With Enamines: Synthesis and Reactivity of 4-Nitrophenyl-1-piperidinostyrene. Synthesis of Pyridazine, Oxadiazole, 1,2,3-Triazole and 4-Aminopyrazole Derivatives

4-Nitrophenyl-1-piperidinostyrene (4) reacts with an aromatic diazonium salt to afford the arylhydrazonal 6. The latter condenses with active methylene compounds to yield pyridazine derivatives, and with hydroxylamine hydrochloride to produce oxadiazole and 1,2,3-triazole derivatives. Compound 12 was reacted with chloroacetonitrile to afford 4-aminopyrazoles 15.