Reduction with chromous chloride

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

In enediones in which two carbonyl groups of a diketone are linked by an ethylenic bond tin [174] and chromous chloride [196] reduce only the double bond, and none of the conjugated carbonyl groups. A double bond conjugated with one carbonyl group only is not reduced. Refluxing cholest-4-ene-3,6-dione with chromous chloride in tetrahydrofuran yielded 49% of 5/S-cholestane-3,6-dione, and a similar reduction of cholesta-l,4-diene-3,6-one gave 5)S-cholest-l-ene-3,6-dione [196]. 

The purity of RDX may be detd by the Chromous Chloride Method of Jamison (Ref 3)- This method consists in the reduction of RDX in an acetic-HC1 soln with chromous chloride and back-titra-... 

Reductive cleavage of 2,4-dinitrophenylhydrazones. Certain 2,4-dinitrophenyl> hydrazones of 3-ketosteroids can be cleaved under mild conditions if the nitro groups are reduced to amino groups by chromous chloride. Thus when the 2,4-DNP of 4,5a-dihydrocortisone 21-acetate in methylene chloride was shaken in a separatory funnel with chromous chloride and dilute hydrochloric acid for 15 min., workup of the organic layer afforded the ketone in 94% yield. Use of a water-immiscible solvent protects the released ketone an inert atmosphere if required can be provided with dry ice. Cortisone 2,4-DNP was cleaved in only 3-5 hrs. and the yield was 60%. DN P derivatives of A -diene-S-ones were completely resistant to hydrolysis. Contributed by Leon Mandell... 

Reduction [1, 150, after formula (4)]. Reduction of a 9 -hromo-l 1/3-acetoxy-A14-3-ketosteroid with chromous chloride does not lead to the expected 1,4,9(11)-triene, but rather to a 5,9-cyclosteroid 103... 

Also obtained from dehydrogriseofulvin by reductive scission with chromous chloride or with zinc in acetic acid [1192],... 

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... 

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). 

Although primary and secondary nitro compounds may be converted, respectively, to aldehydes and ketones by consecutive treatment with alkalis and sulfuric acid (Nef s reaction) the same products can be obtained by reduction with titanium trichloride (yields 45-90%) [565] or chromous chloride (yields 32-77%) [190]. The reaction seems to proceed through a nitroso rather than an aci-nitro intermediate [565] (Scheme 54, route b). 

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)... 

HMX may be detd by the Chromous Chloride Method of Gutmacher Selig (Ref 26b). The method, essentially, consists of the reduction of HMX with CrClj in a di me thy Iform amide ... 

Chromous chloride was used to effect reductive eleavage of the y-lactone (5). In this case reduction with zinc and acetic acid or with calcium and liquid ammonia proceeded very slowly. 

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