Trioxide and Pyridine

C5H5NH" Cr03Cl ). It is made from chromium trioxide and pyridine under acidic conditions in dry dichloromethane (CH2CI2). 

The cis- 1,2-glycols, obtainable from the parent aromatic hydrocarbon by osmium tetroxide hydroxylation, can be converted to the corresponding trans-1,2-glycols by oxidation-reduction, using a mixture of dimethyl sulfoxide, sulfur trioxide, and pyridine, followed by lithium aluminum hydride reduction. The trans- 1,2-glycols can be dehydrated to arene oxides using DMF-DMA as mentioned above. Benzo[a]pyrene 4,5-oxide (28) and 7,12-dimethylbenz[a]anthracene 5,6-oxide (30) have been prepared by this method in 68 and 80% yields, respectively.18... 

Many other reagents and procedures have been developed for oxidizing alcohols. Some are simply modifications of the procedures we have seen. For example, the Collins reagent is a complex of chromium trioxide and pyridine, the original version of PCC. The Jones reagent is a milder form of chromic acid a solution of diluted chromic acid in acetone. 

Chromium trioxide and pyridine have been used to form amides and lactams from tertiary amines. The yields are however only impressive for the preparation of formamides (equation 19). ... 

Peptide aldehydes can be synthesized by backbone attachment of the corresponding amino acetal to a BAL resin 30.b A modification of this method involves the preparation of a peptide alcohol (with the free alcohol group) by side-chain attachment, and after elongation of the peptide chain the alcohol is converted into the aldehyde using sulfur trioxide and pyridine.t l... 

Another modification made off the C-2 position of 1 is the trichloroacetimidate derivate (104), which was prepared by treating 57 with trichloroacetonitrile and DBU in C1CH2CH2C1 at 0 °C to yield product 104 in a 37% yield (Scheme 16) [39], Efforts were also made to remove the C-2 hydroxyl of 57 entirely. Hydroxyl 57 was treated with 1,1-thiocarbonyldiimidazole and catalytic DMAP in CH2C12 to afford imidazole 105 in 64% yield [50], Imidazole 105 was then refluxed with 2,2 -azobis (2-methylpropionitriIe) (AIBN) and tributyltin hydride in toluene to bestow C-2 dehydroxylated 57 in a C-8 epimeric mixture of C-8 a-H and p-H in 13 and 27% yield (106 and 107), respectively [50], Additionally, dilactone 108 was obtained by treating 57 with a mixture of chromium trioxide and pyridine in CH2C12 in a 37% yield [50],... 

B.i. Chromium Trioxide—Pyridine. In 1948, Sisler and co-workers isolated and characterized a stable complex from the reaction of chromium trioxide and pyridine. Sisler did not use this reagent for the oxidation of organic molecules but Sarett and co-workers recognized its utility in the synthesis of steroids. In this connection, alcohol 24 was oxidized to 26 in 89% yield. The reagent, which probably has the trigonal bipyramidal structure shown in 25, proved useful for the general oxidation of primary and secondary alcohols, even in the presence of double bonds and thioethers,. The oxidation usually requires pyridine as a solvent and... 

A modification was introduced by Collins et al., and when applied to the oxidation of alcohols it has come to be known as Collins oxidation. This modification was developed to circumvent the danger inherent in preparing the reagent, deal with the problem of poor yields in the oxidation of primary alcohols to aldehydes, and facilitate isolation of the carbonyl products. The Sisler-Sarett reagent formed by reaction of chromium trioxide and pyridine was first removed from the pyridine solvent and added to dichloromethane, and this mixture was then treated with the alcohol. The oxidation typically required a 5 1 or 6 1 ratio of complex/alcohol, and reaction occurred at ambient temperatures. Cyclohexanol was oxidized to... 

Jones s oxidation of a primary alcohol leads to a carboxylic acid in most cases. A mixture of chromium trioxide and pyridine gives a reagent that can oxidize a primary alcohol to an aldehyde. This is called Collins s oxidation. The reaction of chromium trioxide and pyridine in aqueous HCl leads to pyridinium chlorochromate, called PCC. The reaction of chromium trioxide and pyridine in water leads to pyridinium dichromate (PDC). Both PCC and PDC can oxidize a secondary alcohol to a ketone or a primary alcohol to an aldehyde. 

Draw the products expected when 4,5-diphenyl-8-oxo-nonanol reacts with chromium trioxide and pyridine. 

Form Supplied in crystalline white solid widely available. Preparative Methods reaction of chlorosulfonic acid and pyridine in CHCls or reaction of sulfur trioxide and pyridine. Handling, Storage, and Precautions corrosive reacts quantitatively with hot H2O to give pyridine and sulfuric acid. Use in a fume hood. 

Collins reagent is an adduct of chromium trioxide and pyridine used for diverse... 

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