Pyridinium chlorochromate Corey

Other oxidation procedures were used, e.g., pyridinium chlorochromate (Corey s reagent), and dipyridine Cr(VI) oxide (Collins ... 

The Collins/Sarett oxidation (chromium trioxide-pyridine complex), and Corey s PCC (pyridinium chlorochromate) and PDC (pyridinium dichromate) oxidations follow a similar pathway as the Jones oxidation. All these oxidants have a chromium (VI), normally yellow, which is reduced to Cr(IV), often green. 

These authors also described a three-step synthesis of 13Z-retinoic acid [56], The obtained hydroxydihydropyrane (66%) was oxidized either by Jones s reagent (CrC>3, water, H2SO4, 90%) or Corey s reagent (pyridinium chlorochromate (PCC), 65%). Finally, the dihydropyranone was transformed into retinoic acid (as a mixture of 9E, 13Z, and 9Z,13Z), by /BuOK, according to a known procedure [57], Fig. (26). 

Corey, E. J. and W. Suggs (1975) Pyridinium chlorochromate. An efficient reagent for oxidation of primary and secondary alcohols to carbonyl compounds. Tetrahedron Letters 16,2647-2650. 

Pyridinium chlorochromate (PCC) Corey and Suggs prepared PCC by mixing CrOs with pyridine in HCl. PCC is used for the oxidation of primary and secondary alcohols in CH2CI2. This reagent is less efficient than Collins reagent for the oxidation of allyl alcohols. 

Pyridinium chlorochromate [26299-14-9] M 215.6, m 205 (dec). Dry it in a vacuum for Ihour. It is not hygroscopic and can be stored for extended periods at room temperature without change. If the purity is very suspect, it can be readily prepared. [Corey Scuggs Tetrahedron Lett 2647 1975, Piancatelli et al. Synthesis 245 1982 ] (Possible CARCINOGEN.)... 

Pyridinium Chlorochromate. The need for improved oxidation of primary alcohols and greater ease for isolation of products prompted further research into the nature of Cr(VI) reagents. Corey found that addition of pyridine to a solution of chromium trioxide in aqueous HCl allowed crystallization of a solid reagent characterized as 31, pyridinium chlorochromate (PCC). This reagent was superior for the conversion of primary alcohols to aldehydes in dichloromethane but less efficient than the Collins oxidation when applied to allylic alcohols. Oxidation of 1-heptanol with PCC in dichloromethane gave 78% of heptanal, for example. As stated by Corey, PCC is an effective oxidant in dichloromethane although aqueous chlorochromate species are not very effective oxidants. Oxidation of secondary alcohols to ketones is straightforward, as in Banwell s synthesis of y-lycorane, in which 32 was oxidized by PCC to the ketone (33). ... 

Citronellol added to a suspension of pyridinium chlorochromate in dry methylene chloride, stirred 36 hrs. at 25°, the resulting isopulegone dissolved in ethanol, and heated 1 hr. with NaOH -> (-)-pulegone. Y 71%. - Pyridinium chlorochromate is sufficiently acidic to cause the above ring closure. E. J. Corey, H.E.Ensley, and J.W. Suggs, J. Org. Chem. 41, 380 (1976). 

The Collins oxidation, Jones oxidation, and Corey s PCC (pyridinium chlorochromate) and PDC (pyridinium dichromate) oxidations follow a similar pathway. 

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