Dimethyl sulfoxide-acetic anhydride groups

The use of dimethyl sulfoxide-acetic anhydride as a reagent for the oxidation of unhindered steroidal alcohols does not appear to be as promising due to extensive formation of by-products. However, the reagent is sufficiently reactive to oxidize the hindered 11 j -hydroxyl group to the 11-ketone in moderate yield. The use of sulfur trioxide-pyridine complex in dimethyl sulfoxide has also been reported. The results parallel those using DCC-DMSO but reaction times are much shorter and the work-up is more facile since the separation of dicyclohexylurea is not necessary. Allylic alcohols can be oxidized by this procedure without significant side reactions. 

Useful syntheses of D- and L-lyxose from 1,3-O-benzylidene-D- and L-arabinitol have been achieved through the highly selective oxidation of the primary hydroxyl groups by dimethyl sulfoxide-dicyclohexylcarbodiimide.463 Oxidation of but one of the two (equivalent) hydroxyl groups in 1,3,4,6-tetra-O-benzyl-D-mannitol464 and l,6-di-0-benzyl-2,5-0-methylene-D-mannitol465 was possible with dimethyl sulfoxide-acetic anhydride. 

In an example of the use of this activation method testosterone, with a IT -hydroxy group, was oxidized to A -androstene-3,17-dione very rapidly in high yield, in contrast to the use DMSO-acetic anhydride. During a reaction, when other oxidizing agents were found to be ineffective, sulfur trioxide/dimethyl sulfoxide led to smooth oxidation of the df-diol (16 equation 8) to an o-quinone in 49% yield and the ci.r-diol (17) to (18 equation 9) in 98% yield. - The use of dimethyl sulfoxide-acetic anhydride for this oxidation gave large amounts of the diacetate as the by-product. 

Dimethyl sulfoxide acetic anhydride 2,3-Dihydro-6H-l,3-thiazine ring Oxidative ring closure Protection of alcohol groups as ), ), j -tridilorethyl carbonates Reductive removal of the protective group... 

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... 

Although many oxidizing reagents remove the chromium tricarbonyl group, benzylic alcohols can be oxidized to benzaldehydes using dimethyl sulfoxide with acetic anhydride, trifluoroacetic anhydride, or sulfurtrioxide with minimal decomplexation. Asymmetric oxidation of aUcylthio-substituted complexes can be achieved using titanium tetraisopropoxide and an optically active tartrate ester (Scheme 108). Dimethyloxirane can also be used to oxidize sulfides to sulfoxides. 

The oxidation of diols having alcoholic groups of the same nature, for example, both alcoholic groups are primary, secondary, allylic, or benzylic, is usually carried out at both groups to yield dialdehydes [832] or diketones [552], Such reactions are achieved by chromium trioxide [582], barium manganate [832], dimethyl sulfoxide activated with acetic anhydride [1013], and others (equations 284 and 285). 

Protection of aldoses at the non-anomeric positions makes it possible to use many of the common procedures in organic chemistry for oxidizing lactols as shown with mannofura-nose 1 and glucopyranose 3 (O Table 1). The reactions can be divided into three main categories oxidations mediated by activated dimethyl sulfoxide (DMSO), oxidations with chromi-um(VI) oxides, and oxidations catalyzed by ruthenium oxides. The DMSO-mediated oxidations of alcohols can be promoted by several activators [27]. With the partially protected aldoses the activation has mainly been achieved with acetic anhydride and oxalyl chloride. Competing /3-elimination does usually not occur unless the eliminating group is an ester, e. g., an acetate or a benzoate [27]. 

Horton and Jewell431 examined various reagents for the oxidation to ketones of carbohydrates with isolated secondary hydroxyl groups and concluded that DMSO-Ac20 is the most satisfactory. For a ketone that is water-sensitive, this oxidant has the particular advantage that all reagents can be removed by simple lyophilization. Dimethyl sulfoxide in combination with acetic anhydride effects oxidative re-... 

On the other hand, it has been demonstrated that amylose having the 6-OH group protected by the trityl group reacts with dimethyl sulfoxide in the presence of acetic anhydride to effect oxidation at C-2 and conversion of the 3-hydroxyl group into the methylthiosomethyl ether.2289... 

This reaction was first reported by Albright and Goldman from the American Cyanamid Company in 1965. It is a mild conversion of primary and secondary alcohols into corresponding aldehydes and ketones using the mixture of dimethyl sulfoxide and acetic anhydride as the oxidant. This reaction is particularly useful for the oxidation of the steri-cally hindered hydroxyl groups. In general, the oxidation is carried out by allowing a mixture of 1 mmol primary or secondary alcohol, 3 mL DMSO, and 2 mL (20 mmol excess) acetic anhydride to stand at room temperature for 18-24 h. ... 

A very useful group of procedures for oxidation of alcohols to ketones have been developed that involve dimethyl sulfoxide (DMSO) and any one of a number of electrophilic molecules, particularly dicyclohexylcarbodiimide, acetic anhydride, and sulfur trioxide. The initial work involved the DMSO-dicyclo-hexylcarbodiimide system. The utility of the method has been greatest in the oxidation of molecules that are highly sensitive to more powerful oxidants and therefore cannot tolerate alternative methods. The mechanism of the oxidation involves formation of intermediate A by nucleophilic attack of DMSO on the carbodiimide, followed by reaction of this species with the alcohol. A major portion... 

A mixture of yohimbine, dimethyl sulfoxide, and acetic anhydride allowed to stand 18-24 hrs. at room temp. yohimbinone. Y 80-85%. — This method is particularly useful for the oxidation of sterically hindered hydroxyl groups and compounds, such as indole alkaloids, which are sensitive to non-selective oxidants. F. e. s. J. D. Albright and L. Goldman, Am. Soc. 87, 4214 (1965) carbohydrates s. 289. 

The methylthiomethyl (MTM) group is a related alcohol-protecting group. There are several methods for introducing the MTM group. Alkylation of an alcoholate by methylthiomethyl chloride is efficient if catalyzed by iodide ion. Alcohols are also converted to MTM ethers by reaction with dimethyl sulfoxide in the presence of acetic acid and acetic anhydride or with benzoyl peroxide and dimethyl sulfide. The latter two methods involve the generation of the methylthiomethylium ion by ionization of an acyloxysulfonium ion (Pummerer reaction). 

Dimethyl sulfoxide containing cyclohexylcarbodiimide and an acid, such as phosphoric acid, is increasingly used as a mild selective oxidant . Also a mixture of dimethyl sulfoxide and an acid anhydride, e.g. acetic anhydride, has been found useful for the oxidation of sterically hindered hydroxyl groups and compounds, such ascertain indole akaloids, sensitive to non-selective oxidants . ... 

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