Oxidation with Dimethyl Sulfoxide

To a refluxing solution of 4 g (0.033 mol) of 4,6-octadiyn-l-ol and 21 g (0.10 mol) of dicyclohexylcarbodiimide in 200 mL of absolute ether, a solution of 1.7 g of crystalline phosphoric add in 100 mL (110 g, 1.41 mol, 43 x molar excess) of dimethyl sulfoxide is added dropwise. After an additional heating for 4 h, 100 mL of 4 N sulfuric acid is added. The precipitated crystals of A/,A/ -dicyclohexylurea are filtered with suction and washed with ether. The filtrate is washed until neutral with a solution of sodium hydrogen carbonate. The dried ether solution is evaporated, and the residue is distilled at 60 °C at 0.001 mm of Hg to give a 73% yield of 4,6-octadiynal as a colorless oil. 

A solution of 15.98 g (0.065 mol) of p-bromophenacyl bromide in 100 mL (110 g, 1.41 mol, 38.5 equiv) of dimethyl sulfoxide is kept at room temperature for 9 h. It is then poured into an ice-water mixture and extracted with ether. The extracts are washed with water, dried with anhydrous magnesium sulfate, and evaporated in vacuo. The residual pasty pale-yellow solid is recrystallized from butyl ethyl ether to give 11.2 g (84%) of p-bromophenylglyoxal hydrate, mp 123-124 °C. 

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Cholane-24-ol, oxidation with dimethyl sulfoxide, dicyclohexylcarbo-di-imide, and pyridinium trifluoro-acetate, 47, 25... 

The reaction of the aldehyde 174, prepared from D-glucose diethyl dithio-acetal by way of compounds 172 and 173, with lithium dimethyl methyl-phosphonate gave the adduct 175. Conversion of 175 into compound 176, followed by oxidation with dimethyl sulfoxide-oxalyl chloride, provided diketone 177. Cyclization of 177 with ethyldiisopropylamine gave the enone 178, which furnished compounds 179 and 180 on sodium borohydride reduction. 0-Desilylation, catalytic hydrogenation, 0-debenzyIation, and acetylation converted 179 into the pentaacetate 93 and 5a-carba-a-L-ido-pyranose pentaacetate (181). 

The phenyl 1-thioparatoside 145 was activated with TV-iodosuccinimide and silver triflate and reacted with a convenient derivative of the disaccharide (1-d-GalpNAc-(l ->4)-p-D-GlcpNAc. After removal of the pivaloyl-protecting group with sodium methoxide, isomerization of paratose to tyvelose was performed in a one-pot reaction by oxidation with dimethyl sulfoxide and acetic anhydride, followed by reduction with L-Selectride. Selectivity of the reduction was better... 

J.l Oxidation with Dimethyl Sulfoxide 4.422 Oxidation with Selenoxides... 

The maiin domain of oxidation with dimethyl sulfoxide is the conver-sionofprimary alcoholsinto aldehydes andofsecondaryalcoholsintoketones. These reactions are accomplished under very mild conditions, sometimes at temperatures well below 0 °C. The reactions require the presence of acid catalysts such as acetic anhydride [713, 1008, 1009], trifluoroacetic acid [1010], trifluoroacetic anhydride [1011, 1012, 1013], trifluorometh-anesulfonic acid [1014], phosphoric acid [1015, 1016], phosphorus pentox-ide [1006, 1017], hydrobromic acid [1001], sulfur trioxide [1018], chlorine [1019, 1020], A -bromosuccinimide [997], carbonyl chloride (phosgene) [1021], and oxalyl chloride (the Swem oxidation) [1022, 1023, 1024], Dimethyl sulfoxide also converts sufficiently reactive halogen derivatives. into aldehydes or ketones [998, 999] and epoxides to a-hydroxy ketones at -78 °C [1014]. 

A modification of alcohol oxidation with dimethyl sulfoxide is the reaction of DMSO with alkyl chloroformates, which are formed from alcohols and phosgene (equations 220 and 221) [1021]. 

In more recent works, the use of dicyclohexylcarbodiimide has been abandoned because the reaction works satisfactorily with acid catalysts alone, followed by bases such as triethylamine or diisopropylethylamine, which gives, sometimes, even better yields than triethylamine [1012,1023. Several activators are being used, and the best seems to be oxalyl chloride (theSwern oxidation) [1023,1149]. Other activators are mentioned in the section Oxidation of Primary Alcohols to Aldehydes. The advantages of oxidations with dimethyl sulfoxide lie in the mildness of the reagent and in the low temperatures, sometimes -45 °C [1020] or -60 °C [1023], at which the reactions are run. 

The disadvantages of oxidations with dimethyl sulfoxide are the large excess of the oxidant needed and the obnoxious smell of the dimethyl sulfide formed. Therefore, oxidations with this reagent should be carried out in hoods. 

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