الفهرس 
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Abstract
English Summary
This study involving the synthesis of various new hetrerocyclic compounds during reaction of N-substituted hydrazinecarbothioamides (thiosemicarbazones) and N,N’-disubstituted hydrazinecarbothioamides (disubstituted 2,5-dithioureas) as electron donors with selected electron deficient compounds. The structure of the isolated products, were proved by NMR (including 2D-NMR), mass, IR spectra and elemental analyses. The mechanism of the products formation was also discussed.
i) The electron donors used in this study are:
a) Thiosemicarbazones 1a-f
• (E)-2-Benzylidenehydrazinecarbothioamide (1a)
• (E)-2-(4-Methylbenzylidene)hydrazinecarbothioamide (1b)
• (E)-2-(4-Methoxybenzylidene)hydrazinecarbothioamide (1c)
• (E)-2-(Benzo[d][1,3]dioxol-5-ylmethylene)hydrazinecarbothioamide (1d)
• 2-Cyclohexylidenehydrazinecarbothioamide (1e)
• (E)-2-(4-Chlorobenzylidene)hydrazinecarbothioamide (1f)
b) 1,6-Disubstituted 2,5-dithioureas 2a-d:
• N1,N2-Diphenylhydrazine-1,2-bis(carbothioamide) (2a)
• N1,N2-Di-p-tolylhydrazine-1,2-bis(carbothioamide) (2b)
• N1,N2-Dibenzyl-hydrazine-1,2-bis-(carbothioamide) (2c)
• N1,N2-Diallylhydrazine-1,2-bis(carbothioamide) (2d)
ii) The electron acceptors used in this study are:
a) Activated nitriles 3a,b and 4a,b
• (Z)-Ethyl 2-cyano-3-phenylacrylate (3a)
• 2-Benzylidenemalononitrile (3b)
• Ethyl 2-cyano-3,3-bis-(methylthio)acrylate (4a)
• 2-Bis-(methylthiomethylene)malononitrile (4b)
b) 2-Bromoacetophenones 5a,b:
• 2-Bromo-1-phenylpropan-1-one (5a)
• 2-Bromo-1,2-diphenylethanone (5b)
The present work consists of three parts:
2.1. Reactions of thiosemicarbazones 1a–e with activated nitriles 3a,b or arylaldehydes
In this part, we reacted the electron donors 1a-e with activated nitriles 3a,b or aldehydes in dimethyl formamide (DMF) as a solvent and catalyzed by triethyl amine (Et3N), aiming to prepare the expected thiazoles 6 (Scheme 1). However the reaction gave the symmetric and asymmetric azines 7a-c and 8b-e as shown in Scheme 1. On repeating the same procedure using microwave (MW) irradiation, the reaction proceeded to give the corresponding azines in very good yields comparing with those in the previous traditional method. The mechanism describes the formation of azines was based upon salt formation 9, which would loss NH3 to give the corresponding isothiocyanates 10. Reaction of 10 with either activated nitriles 3a,b or arylaldehydes furnished various types of azines as shown in Scheme 1 .
In different manner, the reaction of 1f with either 3a or 3b and under MW, produced only the dimer assigned as disulfide 11.
The following compounds were synthesized:
• (1E,2E)-1,2-Dibenzylidenehydrazine (7a)
• (1E,2E)-1-Benzylidene-2-(4-methylbenzylidene)hydrazine (7b)
• (1E,2E)-1-Benzylidene-2-(4-methoxybenzylidene)hydrazine (7c)
• (1E,2E)-1,2-Bis(4-methylbenzylidene)hydrazine (8b)
• (1E,2E)-1,2-Bis(4-methoxybenzylidene)hydrazine (8c)
• Anti-1,2-bis(benzo[d][1,3]dioxol-5-ylmethylene)hydrazine (8d)
• 1,2-Dicyclohexylidenehydrazine (8e)
• Dimer assigned as disulfide 11
2.2. Reactions of bisthioureas 2a-d with either 2-bis(methylthiomethylene) malononitrile (4a) or ethyl 2-cyano-3,3-bis-(methylthio)acrylate (4b)
Bisthioureas reacted with 4a or 4b to give 1,3,4-thiadiazoles 12a-c (Scheme 2). Only,
the reactive allyl derivative of bisthioureas 1d reacted with 4a,b to give 1,3-thiazoles 13a,b (Scheme 2).Our method is a valuable addition to the literature for the synthesis of this class of compound in good yields without requiring the aforesaid hazardous acidic conditions (Scheme 2). X-ray structure analysis of compound 12b was obtained as shown in Figure 1. The mechanism of the products formation was also discussed.
The following compounds were synthesized:
• N,N’-Diphenyl-1,3,4-thiadiazole-2,5-diamine (12a)
• N,N’-Bis-4’-methylphenyl-1,3,4-thiadiazole-2,5-diamine (12b)
• N,N’-Bis-benzyl-1,3,4-thiadiazole-2,5-diamine (12c)
• Z-N-Allyl-2-(3-allyl-4-cyano-5-(methylthio)thiazol-2(3H)ylidene)hydrazine-1- carbothioamide (13a)
• Ethyl (Z)-3-allyl-2-(3-allylcarbamothioyl)hydrazono-5-(methylthio)-2,3-dihydrothiazole-4-carboxylate (13b)
2.3. Reaction of N,N’-disubstituted hydrazinecarbothioamides 2a-d with 2-bromo-2-substituted acetophenones 5a,b
This part described the synthesis of different types of heterocycles (thiazole-, bis-thiazole-, pyrazole- and 1,3,4-thiadiazole derivatives ) during reaction of N,N’-disubstituted-hydrazine-carbothioamides 2a-d with 2-bromoacetophenones 5a,b in ethanol at room temperature (Scheme 3). The structure of the obtained products was proved by NMR (2D-NMR), IR, mass spectra and elemental analyses as well. The mechanism showed the products formation was also fully discussed. The single-crystal X-ray diffraction study was carried out on compounds 18da and 19ab and showing the bis-thiazole and pyrazole system (Figure 2).
The following compounds were synthesized:
• N-Phenyl-2-(3,4,5-triphenylthiazol-2(3H)-ylidene)hydrazine-1-carbothioamide (14cb)
• N-Benzyl-2-(3-benzyl-4,5-diphenylthiazol-2(3H)-ylidene)hydrazine-1-carbothioamide (15bb).
• N-Benzyl-2-(3-benzyl-5-methyl-4-phenylthiazol-2(3H)-ylidene)hydrazine-1-carbothioamide (16ba)
• 2-(4,5-Diphenyl-3-(p-tolyl)thiazol-2(3H)-ylidene-N-(p-tolyl)hydrazine-1-carbothioamide (17db).
• (1E,2E)-1,2-Bis(5-methyl-4-phenyl-3-(p-tolyl)thiazol-2(3H)-ylidene)hydrazine (18da)
• N-Allyl-4,5-diphenyl-1H-pyrazol-3-amine (19ab)
• N,N’-Diphenyl-1,3,4-thiadiazole-2,5-diamine (20a)