Chromic anhydride-Pyridine

Oxidation of O-methyldeacetyllythramine (75) with chromic anhydride-pyridine complex yielded the ketone (79) which exchanged four hydrogens on treatment with sodium deuteroxide in deuterium oxide and deutero-methanol (12). 

The Wittig reaction of dialdehyde 175, prepared by chromic anhydride-pyridine oxidation of diol 94 (53), with 176 in dilute methylene chloride solution produced cyclophane 177 in 86% yield. Epoxidation of 177 with m-chloroperbenzoic acid followed by hydrogenolysis over Pd/C, acetylation, and PtOz-Raney Ni-catalyzed hydrogenation afforded the cis-substituted piperidine derivative (178). 

A4 -Cholestcne-3-one, 269 As-Cholestene-3-one, 380 A4-Cholestenyl acetate, 265 A9( 1 )-Cholestenylacetate, 265 Cholesteryl acetate, 51 Cholesteryl phosphorodichtoridate, 390 Cholic add, 252,416 Chromic acid, 95-96 Chromic anhydride, 96-97 Chromic anhydride in graphite, 97 Chromic anhydride-Pyridine, 96, 304 Chromium(II)-amine complexes, 97 Chromium(lll) chloride, 162 Chromium hexacarbonyl, 346 Ouomium(II) perchlorate, 97 Chromous acetate, 97-98 Chromous chloride, 506 Chromyl chloride, 98-99 Qnnamaldehyde, 97,269,406 Cinnamic alcohol, 97 Cinnamyl acetate, 322... 

Chlorotrifluoromethylcarbene, 223 N-Chlorourethane, 60, 61 AM-Cholestadiene-3,6-dione, 60 5a-Cliolestane-3,6-dione, 60 5oCholestane-2a , 3a-oxide, 135 5CfrCholestane-2j3,3(3-oxide, 135 5(3-Cholestanone-3,6-dione, 60 A4-Cholestene-3,6-dione, 60, 65 Al-5/3-Cholestene-3,6-dione, 60 A4-Cholestene-3-one, 98 A4-Cholestene-4-one, 60 -Cholestene-a-epoxide, 116 A5-Cholestenone, 65 Cholesteryl acetate, 35, 171 Cholesteryl acetate dibromide, 40 Chromic acid, 54, 246 Chromic anhydride, 54-57, 150 Chromic anhydride-Acetic acid, 56 Chromic anhydride-Dimethylformamide, 56 Chromic anhydride-Pyridine complex,... 

Deoximation. Jones reagent and chromic anhydride-pyridine (3,55-56 4, 96) have been added to the known reagents for oxidative deoximation. The former reagent was used in acetic acid rather than acetone for solubihty reasons. Periodic acid also can be used, but it sometimes gives rise to iodinated products. ... 

Chromic anhydride-pyridine, 70 Chromium hexacarbonyl, 71 Chromones, 423 Chromous chloride, 73 Chrysanthemic acid, 49, 50, 207-208 Chrysanthemic esters, 183-184 Cinnamic esters, 362 CitroneUol, 5, 308, 309 Claisen rearrangement, 2, 372 Clemmensen reduction, 426 Cocaine, 384 Codeine, 236, 347, 348 Conjugate addition, 86, 102, 119-120, 133, 226-227, 253, 353, 400 Cope rearrangement, 66, 397 Copper, 73-74 Copper(I) acetate, 80 Copper(II) acetate, 39, 117, 126, 186 Copper(I) bromide-Lithium trimethoxy-aluminum hydride, 80 Copper(I) bromide, 79-80 Copper(I) chloride, 50, 80-81 Copper(II) chloride, 126, 79 Copper(l) cyanoacetate, 74 Copper halide nitrosyls, 73 CopperO) iodide, 81-82 Copper(I) methyltrialkylborates, 4,75 CopperGD perchlorate. 79 COpper(I) phenylacetylide, 237 Copper(II) sulfate, 117 CopperO) trifluoiomethanesulfonate, 75-76... 

The relationship between dihydrofurospongin-2 (74) and furospon-gin-1 (70) was established by converting the latter to the former, using chromic anhydride-pyridine complex. 

Attempts at mild oxidation of dimethyldecodine (14) to the lactam with neutral potassium permanganate in acetone or chromic anhydride in pyridine were unsuccessful and only the starting material was recovered. 

Hofmann degradation of 0,7V-dimethyllythranidine (77) methiodide followed by catalytic hydrogenation gave a product whose methiodide underwent the same sequence of reactions yielding de-iV-product 80 (mp 133.5-135°). Oxidation with chromic anhydride in pyridine afforded a diketone 81 (mp 116-118°). 

Hydroxymethylation of ketone (155) was followed by protection of the aliphatic hydroxy group (2-methoxypropyl ether) and addition of an a-benzyloxymethylene group at C-4. Acidic workup at the last stage of the reaction sequence produced (156). Its transformation to aldehyde (157) was carried out by successive treatment with methoxypropyl ether, acetic anhydride and pyridine, hydrochloric acid and methanol, and finally chromic acid, pyridine and hydrochloric acid. Dehydration of (157) led to the formation of (158) in 20% yield. Reagents other than the mentioned produced appreciable quantities of the cis A/B isomer. The butenolide (159) was finally synthesized by oxidation and hydrogenolysis. In order to complete the synthesis of triptolide it was necessary to introduce the... 

OXIDATION, REAGENTS Dimethylsulf-oxide-Acetic anhydride. /-Amyl hydroperoxide. N-Bromosuccinimide. Ceric ammonium nitrate. Chloramine. o-Chlo-ranil. 1-Chlorobenzotriazole. N-Chloro-succinimide-Dimethyl Sulfide. Chromic acid. Chromic anhydride. Chromyl chloride. Cobalt(II) acetate. Cupric acetate monohydrate. Cupric nitrate-Pyridine complex. 2,3-Dichloro-5,6-dicyano-l, 4-benzoquinone. Dicyclohexyl-18-crown-... 

The preparation of the complex calls for comment. The directions call for adding 1 part of chromic anhydride in portions with swirling or stirring to 10 parts of pyridine. The first phase of the reaction, particularly if the pyridine is colder than 15°, appears to consist in slow solution of the anhydride without complex formation. After a few minutes the red anhydride is transformed exothermally into a yellow solid, which dissolves rapidly on swirling (below 30°). After about one third of the anhydride has been added and mostly dissolved, the yellow complex begins to precipitate. When the pyridine was added to the chromic anhydride, the mixture usually inflamed. 

A reexamination of this plant established the presence of no less than 10 alkaloids and of these the structures of three were determined. Details of the isolation were not recorded but the data leading to the structures are largely documented. The three alkaloids are spirodane-A, C20N25O2N (mp 281° methiodide, mp 330°) spirodane-B, C20H27O2N (mp 259°) and spirodane-C, C22H29O3N (mp 248°). Spirodane-A upon sodium boro-hydride reduction generates spirodane-B, which can be reconverted to the former by means of chromic anhydride in pyridine. Hydrolysis of... 

The synthesis of racemic bacterioruberin (456), reported in 1979, was the first synthesis of a Cso-carotenoid [28,30]. Oxidation of lavandulol (150) with chromic anhydride and pyridine gave lavandulal (151) which was elongated with the Cs-phosphonate 28 in a Horner-Emmons reaction to provide the ester 152. The regioselective diepoxidation with MCPBA resulted in the ester 153. Opening of both epoxides and simultaneous reduction of the ester group with LiAlH4 led to the triol 154 which was converted, with triphenylphosphine hydrobromide, into... 

Trialkylstannyl-lithium reacts with secondary alkyl halides (substitution) and with a/S-unsaturated carbonyl compounds (conjugate addition) to give alkyl tin derivatives which may be oxidized with chromic anhydride in pyridine to give a saturated ketone. Applying the procedure to a cycloalkenone, an efficient dialkyl-ative enone transposition can be realized (Scheme 68). ... 

The 6a-hydroxyl group in ty-muricholic and hyocholic acid was verified by the identification of hyodeoxycholic acid derived from these trihydroxy acids. After acetylation in a mixture of acetic anhydride and pyridine at room temperature, hyocholic acid yielded a diacetate whereas cy-muricholic acid yielded both a diacetate and a triacetate. The diacetates were oxidized with chromic anhydride and an ethylenedithioketal was prepared, which after desulfuration with Raney nickel yielded hyodeoxycholic acid [Hsia et al. (45)]. 

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