Reduction of the 1,2,5-thiadiazole ring of 3,6:12,15-di-1,4-benzo[6.6](3,4)-1,2,5-thiadiazolo- and 3,5:11,13-di-1,3-benzo-[6.6](3,4)-1,2,5-thiadiazolocyclophanes. Selective preparation of cis- and trans-[23]cyclophane-1,2-diacetoamide

The effect of the [2.2.2]cyclophane ring structure on the reduction of 1,2,5-thiadiazole ring incorporated in cyclophanes 1a-c and 2a-c was investigated. When reduced by sodium metal in ethanol followed by acetylation, para[2³]cyclophane 1 gave a mixture of the expected cis- and trans-diamides, 3 and 4 , in which 4 was the major product. On the other hand, reduction of 1 with lithium aluminum hydride proceeded in a cis-selective manner and gave 3 as a major product after a treatment of the reduced products with acetic anhydride. The reduction of metacyclophane 2 , which is less strained than 1 , proceeded exclusively in cis-fashion and a subsequent treatment of the reduction product with acetic anhydride gave only cis-diamide 6 .     

The chemistry of 1,2,5-thiadiazoles V. Synthesis of 3,4-diamino-1,2,5-thiadiazole and [1,2,5] thiadiazolo[3,4-b]pyrazines

The o-diamine, 3,4-diamino-1,2,5-thiadiazole ( 2 ), was synthesized from 3,4-dichloro-1,2,5-thiadiazole ( 3 ) hy three methods. Aqueous glyoxal cyclized 2 into [1,2,5]thiadiazolo[3,4–6]-pyrazine ( 14 ). 3,4-Dichloro-1,2,5-thiadiazole 1,1-dioxide ( 18 ) reaeted with 2 to give 1,3-dihydro-bis[1,2,5]thiadiazolo[3,4-b:3′,4′-e]pyrazine 2,2-dioxide ( 19 ). The reaction of 2 with selenium oxyehloride led to [1,2,5]selenadiazolo[3,4-c] [1,2,5]thiadiazole ( 12 ). Ring closure of 2,3-diaminoquinoxaline ( 4 ) with thionyl chloride or selenium oxychloride gave [1,2,5]thiadiazolo-[3,4-b]quinoxaline ( 21 ) and [1,2,5]selenadiazolo[3,4-b]quinoxaline ( 22 ), respectively. Sulfurous acid reduced 21 to the 4,9-dihydro derivative 23 , which was reoxidized to 21 with chloranil. Aqueous hase hydrolyzed 21 to 4 via the hydrated intermediate 24 . Aqueous glyoxal cyclized 4 to the covalent hydrate of pyrazino[2,3-b]quinoxaline ( 26 ), 27 , which was dehydrated to 26 . Compound 26 underwent rapid addition of two alcohols in a process analogous to covalent hydration.     

4-Methyl-1,2,5-oxadiazole-3-carbonitrile in the synthesis of 1,2,5-oxadiazolyl-1,2,4-oxadiazoles

4-Methyl-1,2,5-oxadiazole-3-carbonitrile reacts with hydroxylamine to form 4-methyl-1,2,5-oxadiazole-3-carboxamidoxime, which turned out to be the useful starting compound in the synthesis of 3-(1,2,5-oxadiazol-3-yl)-1,2,4-oxadiazoles.     

1,2,4- and 1,2,5-oxadiazoles

It is shown that the first step in the reduction of the investigated oxadiazoles on a dropping mercury cathode in dimethylformamide corresponds to two-electron cleavage of the N-O bond. The degree of reduction is determined by the nature and position of the substituents in the oxadiazole ring and by the rate of protonation of the intermediately formed particles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 38–40, January, 1979.     

Preparation of 3-methyl-4-vinyl-1,2,5-oxadiazole and 3-methyl-4-vinyl-1,2,5-thiadiazole

Short and high yielding preparations of 3-Methyl-4-vinyl-1,2,5-oxadiazole ( 6a ) and 3-Methyl-4-vinyl-1,2,5-thiadiazole ( 6b ) are described.     

1,2,5-Selenadiazoles. Synthesis and properties

4-Amino-1, 2, 5-selenadiazole-3-carboxylic acid and 4-amino-1, 2, 5-selenadiazole-3-carboxamides have been prepared by ring-cleavage of [1, 2, 5]selenadiazolo[3, 4-d]pyrimidin-7(6H)-one by basic reagents. The primary amide (III), as well as an N-alkyl amide, may be produced by the action of a primary amine. Hydrazine reductively cleaves the selenadiazole ring. The preparation of similar 4-ureido derivatives by ring-cleavage of [1,2,5]selenadiazolo[3, 4-d]pyrimidine-5, 7(4 H, 6H)-dione has been demonstrated with two examples. N-Butyl-4-ureido-1, 2, 5-selenadiazole-3-carboxamide is easily hydrolyzed in aqueous base to the corresponding acid, and it has been shown that this reaction proceeds by way of [1, 2, 5]selenadiazolo[3,4-d]pyrimidine-5, 7 (4H, 6H)-dione. The 4-amino-1, 2, 5-selenadiazole-3-carboxylic acid derivatives have marked cytotoxic, antibacterial, and antifungal activity.     

Preparation of 1,2,5-thiadiazole-3-carboxaldehydes

1,2,5-Thiadiazole-3-carboxaldehydes 1a-c were prepared by the acid-catalyzed decomposition of 3-azido-methyl-1,2,5-thiadiazoles 2a-c in 68-83% yields, respectively. Pyrolysis of 2a and 2b afforded the imidazoles 4a and 4b in low yields. NBS -bromination of 1a and 1b gave the corresponding carboxylic acids 10a and 10b via acid bromides 9. Azides 2a and 2b gave the s-triazines 8a and 8b on treatment with NBS.     

The supramolecular chemistry of 1,2,5-chalcogenadiazoles

1,2,5-Chalcogenadiazoles, in particular the tellurium derivatives, are promising building blocks for the assembly supramolecular structures through the formation of the [E-N]₂ (E = S, Se, Te) supramolecular synthon. This short account summarizes initial experimental and computational investigations in this area.     

The conformation and vibrational spectra of trans-1,4-dihalocyclohexanes: Part III. trans-1,4-Diiodo-, trans-1,4-bromoiodo- and trans-1,4-dibromocyclohexane

The IR spectra of trans-1,4-diiodo- and trans-1,4-bromoiodocyclohexane as solutes in various solvents, as pellets and as solids under high pressure are recorded in the region 4000–30 cm^?1. Additional spectra of the melts, amorphous and annealed crystalline solids at 90 K and dichroic spectra of oriented crystals are recorded above 200 cm^?1. Raman spectra of the amorphous and annealed solids at 90 K and as solutes in various solvents, are obtained, including polarization measurements. IR and Raman spectra of trans-1,4-di-bromocyclohexane in the temperature range 90–250 K are recorded. Equilibrium mixtures of ee and aa conformers of the title compounds are observed in solution, in the melts and in the amorphous solid at 90 K. The ee conformer only is present in the stable crystal, while the aa conformer predominates in apparently metastable crystals annealed to ca. 205 K. The concentration of the aa conformer increases under high pressure (50 kbar). Fundamental frequencies for both ee and aa conformers are assigned. A normal coordinate analysis is carried out, and the force Fields adjusted to nine halogenated cyclohexanes using the overlay technique.     

Reduction of 3,4-bis(4-amino-1,2,5-oxadiazol-3-yl)-1,2,5-oxadiazole 2-oxide

Russian Journal of Organic Chemistry -     

Synthesis of trans-1, trans-2, trans-3, and trans-4 bisadducts of C60 by regio- and stereoselective tether-directed remote functionalization

The double Bingel reaction of fullerene C60 with bismalonates attached to a Tr?ger base derived tether afforded trans-1, trans-2, trans-3, and trans-4 bisadducts with excellent regioselectivity. In particular, enantiomerically pure bisadducts with inherently chiral trans-2 or trans-3 addition patterns were prepared starting from enantiomerically pure bismalonates. The absolute configuration of the trans-2 and trans-3 bisadducts was established from their CD spectra. The excellent diastereoselectivity in the double additions to give the trans-2 bisadducts is particularly remarkable given the large distance between the two reacting bonds in opposite hemispheres of the fullerene that is spanned by the tether. Now, all inherently chiral double addition patterns are readily available by tether-directed functionalization using appropriate chiral, nonracemic spacers.