Pyridinium chlorochromate review

Oxidation of 2,5-dialkylfurans with pyridinium chlorochromate results in high yields of a,(3-unsaturated y-dicarbonyl compounds (Scheme 25) (82S245, 80T661). Similar results are obtained by peracid oxidation of furans (see review (90MI206-01)). The acid most frequently used is MCPBA. It is assumed that the first step involves epoxidation as shown in Scheme 25 (83CL1771). 

Oxidation of a primary alcohol gives an aldehyde, and oxidation of a secondary alcohol gives a ketone. Chromium reagents, such as pyridinium chlorochromate (PCC), are commonly used in the laboratory for this purpose (review Sec. 7.12). 

Provide a retrosynthetic analysis and synthesis for each of the following compounds. Review Problem 12.9 Permitted starting materials are phenylmagnesium bromide, oxirane, formaldehyde, and alcohols or esters of four carbon atoms or fewer. You may use any inorganic reagents and oxidizing agents such as pyridinium chlorochromate (PCC). 

The uses of the versatile oxidant pyridinium chlorochromate have been reviewed. Pyridinium chlorochromate has been used for the oxidation of methyl 5-hydroxypentanoate to the aldehyde, an intermediate useful in the synthesis of leukotrienes, and the same reagent oxidatively cleaves secondary vicinal diols to the corresponding aldehydes. The reactivity of the chlorochromate ion as an oxidant can be influenced by the counter-ion. For example, the 4-dimethylaminopyridinium salt is a mild, selective reagent for the oxidation of allylic and benzylic alcohols. Pyridinium fluorochromate oxidizes primary and secondary alcohols to aldehydes and ketones respectively in dichloromethane solution, and shows a less pronounced acidity compared with the chloro-... 

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