Cyclic Thiocarbonates Research Articles

ChemInform Abstract: Potential Anti‐AIDS Drugs. 2′,3′‐Dideoxycytidine Analogues.

Abstract5‐Azacytidine (Ia) is transformed via the protected derivatives (Ib) into the cyclic thiocarbonate (Ic).

The Treatment of Some Cyclic Thiocarbonates With Methyl Halide/Propylene Oxide

Treatment of thiocarbonates (OCSO) with methyl iodidelpropylene oxide at 80� can lead smoothly to the carbonate. In some cases, a competing process is the formation of iodo thiocarbonates ( OCOSMe ), and an explanation is provided for the product distributions observed. The corresponding reactions with methyl bromide and methyl chloride (as methyl chloroformate ) are much less efficient.

ChemInform Abstract: The Deoxygenation of Some Carbohydrate Diols via the Derived Cyclic Thiocarbonate.

AbstractThe thiocarbonates (III) react with (IV) in the presence of "proton sponge" (V) to give the isomers (VI) and (VII).

The Deoxygenation of Some Carbohydrate Diols Via the Derived Cyclic Thiocarbonate

The treatment of methyl 2,6-di-O-methyl-3,4-O-thiocarbonyl-β-D-galactoside with methyl iodide gives mainly the 3-deoxy-3-iodo-D-guloside , whereas the α- anomer of the above and methyl 2-O-methyl-3,4- O- thiocarbonyl-β-L-arabinoside give mainly the 4-deoxy-4-iodo-D- glycosides. An explanation is given for these and some previously reported results. As well, two of the above cyclic thiocarbonates (β-D-galacto and β-L- arabino), together with two cyclic thiocarbonates derived from methyl α-D- mannopyranoside, when treated with tributyltin hydride, gave mixtures (nearly 1:1) of products resulting from deoxygenation . Single-crystal X-ray diffraction structure determination of the β-D- galacto and the β-L- arabino cyclic thiocarbonates showed both pyranose rings to be in the 4C1 conformation.

Regioselectivity in the free radical deoxygenation of diol thiocarbonates involving the tertiary hydroxy group of branched chained sugars

The cyclic thiocarbonates 1 to 3 react with tri(n-butyl)tin hydride under formation of the deoxygenation products 10 , 11 , 12 , and 14 . The unexpected regioselectivity of this reaction with the compounds 2 and 3 will be discussed in the following.

The conversion of some carbohydrate diols into cyclic carbonates and thiocarbonates by means of N-dichloromethylene-N,N-dimethylammonium chloride (Viehe's salt)

Various carbohydrate cis and trans vicinal diols have been treated with N-dichloromethylene-N,N- dimethylammonium chloride (Viehe's salt), and the resulting cyclic salts quenched with water or sodium hydrogen sulfide to form, in the main, cyclic carbonates and thiocarbonates. These results are discussed in light of the 'orbital-assist' proposal by Deslongchamps.

Dithiols. Part XXVII. Conversion of aliphatic and alicyclic carbonates and thiocarbonates into trithiocarbonates

Reaction of the carbonates of ethane-1,2-, propane-1,2-, meso-butane-2,3-, DL-butane-2,3-, and cyclohexane-cis-1,2-diol with sodium (or potassium)O-ethyl xanthate gave the corresponding trithiocarbonates with (when detectable) a net inversion of configuration at one of the carbon atoms concerned; better yields were obtained from thioncarbonates. The carbonate and the thioncarbonate from cyclohexane-trans-1,2-diol reacted by a different mechanism and gave the trans-trithiocarbonate. High yields of trithiocarbonates were obtained, with retention of configuration, from several dithiolcarbonates. Reactions on carbonate, thioncarbonate, and dithiol-carbonate analogues in the trans-decalin system proceeded less readily. The transformations into trithiocarbonates involve various mechanisms, some of which require attack on the carbonyl (or thiocarbonyl) carbon atom; others proceed with attack on the ‘alkyl’ carbon atom of the cyclic ester.Mass spectral and i.r. parameters for some cyclic thiocarbonates are tabulated, and the significance of the low-frequency bands is discussed.

The nickel-catalysed carbonylation of 2-mercaptoethanol

Abstract 2-Mercapthoethanol undergoes carbonylation in pyridine solution in the presence of oxygen and of [Ni(CO) 3 Pyl as a catalyst to give cyclic O , S -ethylelnethiorcarbonate. The isolation of thiolatonickel compound [Ni(SCH 2 CH 2 OH) 2 ] by the oxidation of a solution containing [Ni(CO) 3 Py] and 2-mercaptoethanol, and its reaction with carbon monoxide to give the cyclic thiocarbonate and [Ni(CO) 3 Py] prove that the reaction proceeds in at least two steps.

Composés Oléfiniques et Acétyléniques. IV. Nouvelles Synthèses du 1,3,5‐Hexatriene; Électrodimérisation de L'Acroléine sur un Couple Zinc‐Cuivre

AbstractThe electrodimerisation of acroleine on a zinc‐copper couple in the presence of acetic acid gives 1,5‐hexadiene‐3,4‐diol 5 in 76% yield, the ratio meso/dl being 60/40. Gas chromatographic analysis of the reaction mixture reveals the presence of threo‐ and erythro‐1‐hexene‐3,4‐diol and of the mono‐ and di‐acetates (meso/dl) of 4, especially when large quantities of acetic acid are used. Optimum conditions are described in order to minimize these side‐reactions. Starting from 4, two new routes to 1,3,5‐hexatriene 1 has been developped, namely by treating the bistosylate derivative of 4 with sodium iodide in 2‐(2‐ethoxy‐ethoxy) ethanol (adaptation of Linstead's reaction) and by a modification of Corey's method, where 4 is treated with N′, N′‐thiocarbonyl‐diimidazole and the resulting cyclic thiocarbonate decomposed in triphenylphosphite. Hexatriene is obtained respectively in 52 and 47% overall yield, the cis/trans ratios being 10/90 and 20/80. Although these reaction schemes appear to be non‐stereospecific, they constitute two new valuable methods to cis‐1,3,5‐hexatriene.

228. Dithiols. Part XXII. Isopropylidene derivatives and cyclic thiocarbonates from trans-dithiols and from trans-mercapto-alcohols

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