Chromous chloride preparation

REDUCTION WITH CHROMOUS CHLORIDE Preparation of Chromous Chloride [75 ]... 

Reduction of halides. Chromous chloride (prepared by reduction of chromic chloride with zinc powder) has been used to reduce the exo chlorine atom of (1), prepared by Diels-Alder reaction between cyclopentadiene and thiophosgene followed by oxidation of the sulfide group to the sulfone.2... 

Ghromium(II) Compounds. The Cr(II) salts of nonoxidizing mineral acids are prepared by the dissolution of pure electrolytic chromium metal ia a deoxygenated solution of the acid. It is also possible to prepare the simple hydrated salts by reduction of oxygen-free, aqueous Cr(III) solutions using Zn or Zn amalgam, or electrolyticaHy (2,7,12). These methods yield a solution of the blue Cr(H2 0)g cation. The isolated salts are hydrates that are isomorphous with and compounds. Examples are chromous sulfate heptahydrate [7789-05-17, CrSO 7H20, chromous chloride hexahydrate... 

A nickel-chromium catalyst prepared from chromous chloride and (p-diphenylphos-phinopolystyrene)nickel dichloride mediates the ring-closure of the ene-allene 236 (R = H) to a mixture of 3.4 parts of 237 and 1 part of 238 (equation 120)121. An analogous reaction of the t-butyldimethylsilyl ether of 236 yields solely the (E)-isomer 237 (R = t-BuMeaSi). Cyclization of the ene-allene 239 affords the perhydroindane 240 in 72%... 

Divalent chromium salts show very strong reducing properties. They are prepared by reduction of chromium(III) compounds with zinc [187] or a zinc-copper couple and form dark blue solutions extremely sensitive to air. Most frequently used salts are chromous chloride [7SS], chromous sulfate [189], and less often chromous acetate. Reductions of organic compounds are carried out in homogeneous solutions in aqueous methanol [190], acetone [191], acetic acid [192], dimethylformamide [193] or tetrahydrofuran [194] (Procedure 37, p. 214). 

Repare ferric ammonium sulfate (Fe alum) (0.05N) by dissolving 50g in 800 ml of water in a 2 liter volumetric flask. Add 50 ml coned H2S04 and dilute to volume. Prepare chromous chloride (0.05N) by dissolving 27.5g CrCl3. 

Erythrinadienols have also been transformed to dibenzazonines. Thus, when 93 was heated with HC1 in MeOH, a 50% yield of the pentasubstituted dibenzazonine 94 was obtained (Scheme 24). This compound could also be prepared directly from 92 by chromous chloride reduction (70). Erysodienol (95)... 

Use of the chiral carbon pool for cyclopentenone preparation is also known. The fungal metabolite terrein [88] was selectively monoacetylated and then reduced with chromous chloride to enone [89]. Acetylation and olefin cleavage with ruthenium tetroxide aiwi sodium periodate led to aldehyde [90], which was readily decarbonylated to [65] (51). An alternative route (52) began with the less common S,S-tartaric acid [91], converted in four steps to diiodide [92]. Dialkylation of methyl methylthiomethyl sulfoxide with [92] gave the cyclopentane derivative [93]. Treatment of [93]... 

Dehalooenation Chromous chloride. Copper powder-Benzoic acid. Dimethyl sulfoxide-NaH. Hydrazine-Palladium. Iron pentacarbonyl. Lithium-l-Butanol-THF. Magnesium-Iodine-Ether. Methyllithium. Sodium acetate. Sodium iodide. Zinc dust. Zinc dust-Ethanol (see Allene, preparation. Hexafluoro-2-butyne, preparation). 

Reduction with borohydride, chromous chloride, or zinc and hydrochloric acid then affords the hydroxyamine in high yields. Various D-homo-16,17- and 17a-ketones have been prepared by standard methods. Surprisingly, the displacement of 17aj5-tosyloxy-D-homosteroids by azide occurs with retention of configuration. ... 

The Chemistry of Ringc.—The modification of ring c has centred on making available relays that are suitable for elaboration into more complex diterpenoids, the diterpenoid alkaloids, and triterpenoids. The unsaturated ketone (53) has proved to be a valuable relay for synthesis. It had been prepared previously from neoabietic acid, which is difficult to obtain pure. It has now been obtained from the levopimaric acid-formaldehyde adduct (50). Oxidation of the adduct with potassium permanganate not only formed the glycol but in an unusual step converted the cyclic ether into the (5-lactone (51). Dehydration, ozonolysis of the newly formed double bond, and then treatment of the keto-acetate (52) with chromous chloride afforded the a -unsaturated ketone (53). The last step involved hydrogenolysis, / -elimination. and decarboxylation. 

X 10 ii per cent. C. F. Schonbein, N. Bunge, Z. Roussin, and C. W. Vincent prepared a mercury-chromium alloy or chromium amalgam, by the action of potassium or sodium amalgam on a cone. soln. of chromic chloride and H. Moissan obtained the amalgam by a similar process, as well as by the action of sodium amalgam on chromous chloride, bromide, or iodide. R. Myers obtained it by the electrolysis of a soln. of chromic sulphate in dil. sulphuric acid using a platinum anode, and mercury cathode J. Feree found that with a soln. of chromic chloride the yield is poor. 

C. Poulenc i prepared chromium difluoride, or chromous fluoride, CrFg, by the action of hydrogen fluoride on red-hot chromium and by the action of hydrogen fluoride on chromous chloride at ordinary temp. A. Mourlot obtained it by the action of hydrogen fluoride on chromous sulphide. G. Herrmann did not obtain good yields in the electrolytic reduction of chromic fluoride soln. 

W. Traube and co-workers prepared cone. soln. of chromous chloride by the prolonged electrolytic reduction of aq. sola, of green chromic chloride, using lead plates as electrodes and employing a current desnity of 0-175 amp. per sq. dm. The electrolysis of chromous chloride soln., using an iron cathode, results in the formation of a cathodic deposit of metallic chromium mixed with chromium oxides. 

As indicated above, H. Moissan obtained what he regarded as a hexahydrate by evaporating aq. soln. of chromous chloride but A. Eecoura, G. Bauge, and W. A. Knight and E. M. Eich showed that the product is the tetrahydrate, CrCl2.4H20, and they recommended the following mode of preparation ... 

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