Swern—Moffatt oxidation yields

All of the usual chromium-based oxidation reagents that have been used for the oxidation of cyclobutanols to cyclobutanones, for example, chromium(VI) oxide (Jones reagent),302 pyri-dinium chlorochromate,304 pyridinium dichromate,307 and chromium(YI) oxide/pyridine (Collins),303 are reported to do so without any serious problems. Alternatively, tetrapropylam-monium perruthenate in the presence of A-methylmorpholine A -oxide. oxalyl chloride in the presence of triethylamine in dimethyl sulfoxide (Swern),158,309,310 or phenyl dichlorophos-phate in the presence of triethylamine and dimethyl sulfoxide in dichloromethane (Pfitzner-Moffatt),308 can be used. The Pfitzner-Moffatt oxidation procedure is found to be more convenient than the Swern oxidation procedure, especially with respect to the strict temperature control that is necessary to achieve good yields in the latter, e.g. oxidation of 1 to give 2.308... 

In an enantioselective synthesis of a key intermediate for the preparation of poisons from the skin of tropical frogs, a key oxidation was performed under Swern conditions with 77% yield, while PCC provided a 28% yield and Pfitzner-Moffatt oxidation 73% yield. 

But the Pfitzner-Moffatt oxidation is not in much use because the Swern oxidation gives better yield and fewer side products. For example, methyl 12-hydroxydodecanoate (7.11) on treatment with DMSO and oxalyl chloride [(COCl)2] in CF12C12 followed by treatment with triethylamine yields 87% methyl 12-oxododecanoate (7.12). 

Primary alcohols possess a substantially less crowded environment than secondary ones. Thus, in the absence of dominant electronic factors, many oxidants tend to react quicker with primary alcohols. These include many common oxidants, like TPAP,1 PCC,2 Parikh-Moffatt,3 Dess-Martin,4 IBX5 and Swern,6 that are sometimes able to perform selective oxidations of primary alcohols in useful yields, regardless of the fact that they were not devised for this purpose. 

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