Thio-oxalates

Chelate-forming ligands are widely represented amongst oxygen- and sulfur-containing donors [1, vol.2 112,934]. On their basis the following complexes have been isolated monothiocarboxylates 537 [1, vol.2], thio-oxalates 538 [934], and monothio-p-diketonates 539 [1, vol.2 935-937] ... 

The electrochemical behavior of trithio-orthoesters under oxidative conditions is far more complex from the mechanistic point of view than that of thioacetals. Examples, which may be considered as representatives of this class of compounds, are two types of thio oxalates, XXXVI and XXXVII. The oxidation of XXXVI in MeCN was shown to produce well-known tetrathioethylene derivatives, XXXIX and XL [Eq. (93)] [149]. 

Ni(ii) forming 4 coplanar bonds. Planar diamagnetic complexes include the Ni(CN)4 ion, which has been studied in the and other salts (Ni-C, 1-85 A), and molecules such as (a) and (b). The numerous complexes with bidentate ligands include the thio-oxalate ion, (c), molecules of the types (d) ) and (e), and the glyoximes, (0> notable for the short intramolecular hydrogen bonds. Many divalent metals form phthalocyanins, M(ii) replacing 2 H in C32H18N8 (Fig. 27.9). 

The 3-j3-D-arabinofuranosyl pyrazole derivative (33) has been synthesized from D-mannose by the procedure outlined in Scheme 9 on deprotection with ammonia, (33) epimerized to the -D-ribofuranosyl isomer. 2,5-Anhydro-D-allonic acid derivatives have been used to synthesize the C- ym-triazoloribo-nucleosides (34) and (35) by condensation with heterocyclic hydrazine derivatives. The diazoketone (36), prepared conventionally from the acid, has been used to prepare the thiazole analogue (37) of ribavirin via the intermediate a-bromomethyl ketone (38) by condensation with an imido-thio-oxalic acid derivative,and the indazole nucleoside analogue (39) by cyclization with benzyne (Scheme 10). An acyclic diazoketone analogously prepared from D-ribonic acid similarly gave a C-ribonyl-indazole with benzyne, which could be... 

N2H2 is isoelectronic with O2, with two half-filled 7T orbitals that are isolobal with half-filled t2g orbitals on the V(IV) atoms resulting from the electron transfer step. This complex, if it is formed, is too unstable to detect due to the reaction 2N2H2 -> [HN—NH—NH—NH] N2 + N2H4. Similar electron donors to hydrazine (N2H4) are oxalate ( O2C—CO2) and thio-oxalate [OSC—CSO] , which, when oxidized, break the C-C bond, which forms the gases CO2 and CSO. 

A convenient synthesis of medium-sized keto-thiolactones has been developed. The key step is a photosensitized oxygenation of bicyclic thioenol ethers (Scheme 35). A study of thio-oxalates as dithiabutadienes has been carried out, and some unusual sulphur heterocycles have been prepared (Scheme 36). 

In the previous paragraph we have noted two different systems in which metal-ion catalysis of co-ordinated ester hydrolysis has respectively a lower and a higher activation enthalpy than that for hydrolysis of the free ester. In the case of metal-ion-catalysed hydrolysis of ethyl thio-oxalate ( 02CC0SEt) it is noteworthy that whereas hydrolysis in the presence of lead(n) has a higher activation enthalpy than hydrolysis of the free ester, hydrolysis in the presence of magnesium(n) has a lower activation enthalpy (Table I). ... 

Os forms many complexes with nitnte. oxalate, carbon monoxide, amines, and thio ureas. The latter arc important analytically Osmium forms the interesting aromatic sandwich" compound, osmocene. A metallocene is described under Ruthenium. See also Chemical Elements and Platinum and Platinum Group. 

Benzo[6]thienylethylenes are readily obtained by elimination of water from the appropriate alcohol. For example, 3-vinylbenzo[6]-thiophene is conveniently prepared by heating l-(3-benzo[6]thienyl)-ethanol with potassium hydrogen sulfate469,471 or by heating 2-(3-benzo[6]thienyl)ethanol with molten alkali.470 2-Vinylbenzo[fe]thio-phene is obtained by pyrolyzing the acetate of l-(2-benzo[6]thienyl)-ethanol.466,620 Other benzo[6]thiophene alcohols have been dehydrated by heating them with oxalic acid,483 iodine,358,465,467,528 or potassium hydrogen sulfate,465,467 or alone.349,485... 

In very dilute solution the intensity of colour produced is not quite proportional to the amount of iron present—indeed, the more concentrated solution becomes decolorised on dilution, as also by addition of oxalates, tartrates, etc. The decoloration on dilution is usually explained on the assumption that the water hydrolyses the red undissociated salt into yellow colloidal ferric hydroxide and free thio-cyanic acid —... 

These two compounds are readily available by condensation of o-amino (thio)phenol with oxalic acid derivatives. 2,2 -Bibenzoxazole (80) was first prepared more than 70 years ago, but was incorrectly formulated as a benzoxazinobenzoxazine (25HCA16). It is readily prepared by oxidation. 

The ceroid hydroxides are somewhat soluble, and wet La(OH)3-aq turns red litmus blue the yttroid hydroxides are less soluble. For both Groups the caibon-ates are insoluble, and the oxalates (distinction from many M ), fluorides and phosphates are insoluble and more or less insoluble even in (cold) dilute HsO. The nitrates, sulfides and sulfates are soluble the basic nitrates are distinctly less so, but those of Ytd ate more soluble than those of Ced However, the oxalates, double nitrates and double sulfates of Ced are more soluble than those of Ytd. The stable chlorides (La-PrlCfi-THiO and (Y,Nd-Lu)Cl3"6H20, and the bromides and iodides, ate soluble. The perchlorates dissolve easily the bromates [Ln(H20)9](Br03)3 dissolve in the molar range, but the solubilities of hydrated Ln(103)3 are only about 1 mM. 

Synthesis of EDOT from oxalic acid ester and thio-diacetic add ester. 

According to the classical definition. Barton esters are mixed anhydrides of carboxylic acids with thio-hydroxamic acid such as I (Scheme Ij. This class of compound was originally developed to allow the transformation of carboxylic acids to a convenient source of radicals for synthetic application. Even now, they are one of the most important entries to C-radicals. Over time, the scope of the reaction was broadened, allowing the generation of heteroatom-centered radicals, particularly oxyl-, aminyl-, and iminyl radicals of synthetic interest. For these transformations, carbonates and carbamates (II), acetates (IV), and ethers (V) were developed (Scheme 1). Finally, oxalates (III) were used for deoxygenation of secondary and tertiary alcohols. The radical fragmentation reaction of these compounds can be carried out either by irradiation or by thermal activation. Both methods are discussed here briefly. 

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