Ahmed Mousaad

Condensed 1,2,4-Triazines: II. Fused to Heterocycles with Six- and Seven-Membered Rings and Fused to Two Heterocyclic Rings

Publisher Summary This chapter deals with condensed ring systems of 1,2,4-triazines with six and seven-membered heterocycles, and condensed ring systems with triazine in the center. The chapter considers the order of increasing number of heteroatoms in the fused ring and each is followed in turn by a heterocycle fused to a benzene ring. Each fused ring system is arrangedaccording to the order of fusion on the triazine ring. Specifically, the chapter describes pyrido[1 ,2,4]triazines, pyrano[ 1 ,2,4]triazines, diazino[1,2,4]triazines, [ 1 ,2,4]triazino-oxazines, [ 1 ,2,4]triazino-thiazines, triazino[ 1 ,2,4]triazines, triazino-oxadiazine, triazino-thiadiazine, triazino-dioxazines, and heterocyclo-triazino heterocycles. With regard to pyrido[l,2,4]triazines, it is observed that there are eight theoretically possible pyridotriazines. Four of them possess bridgehead nitrogen with faces b , c , d , and f common to the triazine ring. The other four isomers have face e in common. Their UV spectral properties are generally dependent on the position of the pyrido N -atom.

2,3,4-Furantriones

Publisher Summary This chapter focuses on the synthesis of heterocycles from 2, 3, 4-furantriones (2, 3-dioxobutyrolactones). It describes the synthesis of the furantriones and also considers their nitrogen derivatives, which retain the furanone ring and are mostly the starting precursors for the heterocycles in the third and fourth parts. The heterocycles that retain the furanone ring and those that are produced by its rearrangement are also dealt with respectively. The synthesis of compounds possessing the furantrione ring is based essentially on the ready oxidation of the hydroxy tetronic acids. The chapter discusses the nitrogen derivatives of furantriones. The heterocycle may be fused to the furanone ring at various positions. Thus, the fusion may be on C-5 and C-4, C-4 and C-3, or C-3 and C-2. Otherwise the heterocycle may be linked to the C-5 of the furanone ring. Heterocycles from rearrangement of the furanone ring are also discussed.

A Novel Approach for the Synthesis of C-Nucleoside Analogs by Constructing Benzoxazine Rings Linked to a Carbohydrate Moiety

Abstract Dehydrative cyclization of the condensation product of 2, 3, 4, 5-tetra-O-acetyl-galactaryl chloride with anthranilic acid gave 1, 2, 3, 4-tetra-O-acetyl-1, 4-bis(4H-benzoxazin-4-one-2-yl)-galacto-tetritol. Its reaction with aniline in the presence of phosphorus trichloride afforded 1, 4-bis (3-phenylquinazolin-4-one-2-yl)-1, 2, 3, 4-tetra-O-acetyl-galacto-tetritol.

Dehydrative Cyclization of Hydrazones: Synthesis of Pyrazolo and Pyrazolyl Quinoxalines

Abstract A number of 3-(l-arylhydrazono-D-erythro-2,3,4-trihydroxybutyl)-6,7-dimethyl-lH-quinoxalin-2-ones (6–8) as well as the semi-and thiosemicarbazones have been prepared. Their periodate oxidation afforded the corresponding 3-(1-arylhydrazono-glyoxal-l-ýl)-6,7-dimethyl-lH-quinoxalin-2-ones (11–13), and their methylation gave 3-(l-arylhydrazono-D-erythro-2,3,4-trihydroxybutyl)-1,6,7-trimethyl-quinoxalin-2-ones (15–17). The action of alkali on the starting hydrazones (6–8) caused a loss of one mole of water to give 1-aryl-6,7-dimethyl-3-(D-erythro-glycerol-l-yl)-flavazoles (18–20) while the action of acetic anhydride afforded 3-(5-acetoxymethyl-l-arylpyrazol-3-yl)-6,7-dimethyl-lH-quinoxalin-2-ones (21–23).

Synthesis of 3-(L-Threo-Glycerol-l-YL)-6,7-Dimethyl-Pyrazolo[3,4-b]Quinoxalines

Abstract Reaction of dehydro-L-ascorbic acid with 1,2-diamino-4,5-dimethylbenzene and arylhydrazines afforded 3-[l-(aryl)hydrazono-L-threo-2,3,4-trihydroxybutyl]-6,7-dimethyl-lH-quinoxalin-2-ones. Their dehydrative cyclization gave 1-aryl-3-(L-threo-glycerol-1-yl)-6,7-dimethylpyrazolo[3,4-b] quinoxalines, whose acetylation and periodate oxidation were studied.

Mode of formation of quinoxaline versus 2[1 H]-quinoxalinone rings from dehydro-d-erythorbic acid

The mode of formation of the quinoxaline versus 2[1H]-quinoxalinone rings by the reaction of o-diamines with dehydro-D-erythorbic acid has been investigated. The study was carried out by using one and two molar equivalents of 1,2-diamino-4,5-dimethylbenzene (3b) to give 6,7-dimethyl-3-(1-oxo-D-erythro-2,3,4-trihydroxybutyl)-2[1H]-quino xalinone (4b) and 2-(2-amino-4,5-dimethylphenylcarbamoyl)-3-(D-erythro-glycerol-1-yl )- 6,7-dimethylquinoxaline (6), respectively. The former product exists predominantly as the two furanosyl anomers. Sequential reaction of 4a with 3b has been studied, and the location of each diamine in the product was deduced by using 1H-n.m.r. spectroscopy. A mechanism for the reaction is proposed. Acetate and acetal derivatives of the compound are prepared.

Isopropylidenation of 1-Aryl-( L -threo-glycerol-1-yl)-6,7-dimethyl-pyrazol[3,4-b]quinoxalline

Abstract The isopropylidenation of 1-aryl-(-threo-glycerol-1-yl)-6,7-dimethyl-pyrazolo[3,4-b] quinoxaline gave regioselectively the corresponding α-threo-dioxolanes. The role of configuration of the glycerolyl residue in directing the location of the isopropylidene ring is discussed. Although the pyrazolo-quinoxaline ring was shown not to affect the regioselectivity, it has a considerable effect on the chemical shift of the methyl groups of the isopropylidene ring.

Synthesis and Dimroth Rearrangement of 6-Cyano-l,2,4-triazolo- [4,3-a]pyrimidin-5- and 7-ones. A Novel Alkylation with Orthoesters and a New Participation of the Cyano Group in the Rearrangement

Abstract The cyclization products of 5-cyano-2-hydrazino-6-phenyl-3,4-dihydropyrimidin-4-one (6) with one carbon inserting agents have been confirmed to be of the 1,2,4-triazolo[4,3-a]pyrimidin- 5(8H)-ones type and not the respective 7-ones, by comparing their alkylated derivatives 10a, 11a, 27 and 28 with the product from the cyclization of the 3-methyl and 3-benzyl derivatives of 6. A novel alkylation process was found when triethyl orthoformate was used as a cyclizing agent. Dimroth rearrangement of 8, 14, 15, 24, 34 and 36 with 2% ethanolic KOH gave the respective triazolo[1,5-a]pyrimidinone 13, 18, 19, 25, 38 and 40, respectively. Using 10% ethanolic KOH led to a novel participation of the cyano group in the rearrangement whereby 8a gave 7-imino-5-phenyl-l,2,4-triazolo[1,5-a]pyrimidine 22

X-Ray Crystallography of 3-(2-0-Acetyl-1, 3-Dibromo-1, 3-DI-Deoxy-L-Erythro-Glycerol-I-YL)-l-Phenyl-2-Pyrazoline-4, 5-Dione 4-(Phenylhydrazone)

Abstract X-Ray crystallography confirmed the L-erythro-config-uration of 3-(2-0-acetyl-1, 3-dibromo-1, 3-dideoxy-glycerol-l-yl)- 1-phenyl-2-pyrazo line-4, 5-dione 4 -(phenylhydrazone) that results from the reaction of hydrogen bromide in acetic acid with the corresponding of L-threo-glycerol-1-yl- analog.

Regioisomeric formation of the linear 1,2,4-triazolo[4', 3' :2,3][1,2,4]triazino[5,6-b]indole from 3-hydrazino-1,2,4-triazino[5,6-b]indole derivatives

Oxidative cyclisation of the ethylidene derivatives of 5-allyl-3-hydrazino-1,2,4-triazino[5,6-b]indole (7) and 8-bromo-3-hydrazino-5H-1,2,4-triazino[5,6-b]indole (8) gave regioselectively the linear isomers, 10-allyl-3-methyl-1,2,4-triazolo[4′,3′:2,3][1,2,4]triazino[5,6-b]indole (15) and 7-bromo-3-methyl-10H-1,2,4-triazolo[4′,3′:2,3][1,2,4]triazino-[5,6-b]indole (16), respectively. They were also obtained by the dehydrative cyclisation of 5 and 6 respectively with acetic acid as well as by the condensation of the N-allyl- (22) or 5-bromo-isatin (23) with 3,4-diamino-5-methyl-4H-1,2,4-triazole (24). The corresponding allyl derivatives 17 and 18 were also synthesised. Some sugar derivatives of 5 were prepared.