Phosphorus pentoxide/DMSO

In a typical example, 10 mmol of an alcohol, 11 mmol of oxalyl chloride, and 24 mmol of DMSO in 40 mL of dichloromethane react at -60 °C. The mixture is then made alkaline with 50 mmol of triethylamine [1023] (equation 262). In other instances, the molar ratios of the alcohol to DMSO and to the activator (benzoic anhydride) were 1 47 and 1 17, respectively with phosphorus pentoxide as the activator, the respective molar ratios were 1 47 and 1 1 [1009], and with pyridine-sulfur trioxide, they were 1 70 and 1 3 [1018]. Dichloromethane and toluene [1012] are the best solvents. 

Hydrolysis of MA-1,3-Dioxepin Copolymers. IA-MA copolymer (2.00g) was combined with 50ml deionized water and stirred at room temperature for A8 hr. After 12 hr. the dispersion became a homogeneous solution. Evaporation of the water and prolonged drying in vacuo over phosphorus pentoxide at room temperature gave a 2.25g yield of white polymer soluble in THF, MEK, DMF and DMSO. 

IB-MA and ID-MA copolymers (3.0g) were combined with 0.1N hydrochloric acid (80ml). The polymer suspensions were stirred and heated for 12 hr. at 50°C and A hr. at 70°C. Isobutyraldehyde odor was detected coming from the IB-MA system. The polymers were collected, washed with deionized water and dried in vacuo over phosphorus pentoxide at room temperature to obtain slightly yellow colored materials soluble in DMF and DMSO. The IR spectrum of each copolymer exhibited absorptions at 3350, 2650, 1760 (with a shoulder at 1720-1700), 1630, 1165 and 1120 cm-1, with no anhydride absorptions at 1855 and 1775 cm-1 and no cyclic acetal absorptions in the 1200-1000 cm-1 region. The 13C NMR spectra, though not well resolved, clearly showed no methyl protons for the recovered IB-MA and ID-MA copolymers. 

Alcohol oxidations using acid anhydrides, such as acetic anhydride and benzoic anhydride, and phosphorus pentoxide with DMSO, have also been found to proceed in mild conditions to give the corresponding carbonyl compounds in good yields.27-29 The method is general and is especially useful for sterically hindered hydroxyl groups however, the reactions often suffer from concomitant formation of methylthiomethyl ether by-products. 

Onodera et al. developed a reagent for the oxidation of alcohols that used DMSO and phosphorus pentoxide. It is very efficient for the oxidation secondary alcohols, particularly those found in carbohydrates. " The alcohol moiety in 69, for example, was converted to ketone 70 in 65% yield. " The... 

This reaction has been modified using the mixture of DMSO and one of the following reagents benzoic anhydride, polyphosphoric acid, and phosphorus pentoxide. However, it seems that the mixture of acetic anhydride and DMSO is still the best combination for this... 

Other oxidation reactions using DMSO as an oxidant include the Pfitzner-Moffatt Oxidation (DMSO/dicyclohexylcarbodiimide), Swem oxidation (DMSO/oxalyl chloride or trifluoroacetic anhydride), Onodera oxidation (DMSO/phosphorus pentoxide), Parikh-Doering Oxidation (DMSO/pyridine-sulfur trioxide), Corey-Kim Oxidation (dimethyl sulfide/Ai-chlorosuccinimide), and Liu oxidation (DMSO/phenyl dichlorophosphate). 

Other reagents that have been found capable of activating DMSO toward nucleophilic attack include acetic anhydride and phosphorus pentoxide. ... 

An improved synthesis of 1,2-0-cyclohexylidene-myo-inositol in 45 -50% yield utilized the reaction of 1,1-dimethoxycyclohexane with myoinositol in DMSO catalyzed by Nafion-H, a perfluorinated strongly acidic ion exchange resin. Minor products were the 1,2 3 4- 1 2 4,5- and 1,2 5t6-diacetals. The acidic reagent systems, phosphorus pentoxide-trimethylsilyl triflate and phosphorus pent-oxide-boron trifluoride etherate, have proved effective for 0-methoxymethylation of carbohydrate and nucleoside derivatives with dimethoxymethane noteworthy is the compatibility of the reagents... 

Claus and Yycudilik have reported the details of the dehydration reaction catalysed by phosphorus pentoxide between DMSO and aryl amines to afford iminosulphuranes in good yield. Lerch and Moffatt have reported that the DMSO-DCC oxidation reaction could be applied to iminosulphurane synthesis simply by the addition of an aryl amine to the reaction mixture rather than the usual alcohol. In both instances the mechanism probably involved displacement from sulphur by the amine of an oxy-leaving group (a pyrophosphate or a urea). The latter workers found that hydrazines could not be used in the place of the aryl amine, probably because of subsequent intramolecular eliminations by the iminosulphuranes. 

The (—)-menthyl ester group has been employed as a chiral auxiliary in electrophilic glycine derivatives. Modified Swem oxidation of (—)-menthyl glycolate 1879 using phosphorus pentoxide for activation of DMSO instead of oxalyl chloride gave... 

SPIs (in their acidic form) in DMSO solution containing 5 wt. % of phosphorus pentoxide are cast into films which are thermally cured at high temperature and under vacuum [121]. 

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