Alcohols methanesulfonic anhydride

NaHCOs, and methanesulfonic anhydride.Dimethyl sulfoxide in 48% HBr oxidizes benzylic alcohols the aryl aldehydes.Note that Swern oxidation of molecules having alcohol moieties, as well as a disulfide, leads to the ketone without oxidation of the sulfur. Sulfoxides other than DMSO can be used in conjunction with oxalyl chloride for the oxidation of alcohols,including fluorinated sulfoxides and a polymer-bound sulfoxide. ... 

There are many methods for the cleavage of 4,5-dihydrooxazoles once they have served their purpose. An effective method for hydrolyzing them back to carboxylic acids employs trifluoro-methanesulfonic anhydride <92SC13>. Intermediate ring-opened esters (100) are A(-methylated, then saponified to the acids (Scheme 34). The oxazoles may also be converted into aldehydes or nitriles. In a one-pot, two-step procedure, 4,5-dihydrooxazoles are transformed into alcohols (101) <93TIj4893>. Chloromethyl methyl ether converts the dihydrooxazoles into ring-opened amides in the first step, and these are reduced with diisobutylaluminum hydride (Scheme 35). 

Butyl alcohol t-Butyl alcohol, Isopropyl alcohol, Methanesulfonic acid Silica gel Succinic anhydride dehydrating agent, paints Slllporite ... 

Glycosyl mesylates can be converted to glycosides by treatment with alcohols, and have also been used as intermediates in the synthesis of oxyglycals. Preparation of methyl ethers by solvolysis of mesylates in methanol has been reported. Treatment of glycidols with methanesulfonic anhydride yields the epoxy mesylate which can then be treated with tellurium to produce the aUyl alcohol (eq 3). ... 

Sulfonate Formation. The preparation of an alkyl methane-sulfonate from an alcohol can be achieved by treatment of an alcohol with methanesulfonic anhydride in the presence of pyridine or 2,4,6-collidine (eq 1). The use of methanesulfonic anhydride rather than methanesulfonyl chloride eliminates the formation of small amounts of alkyl chlorides which occurs when... 

Oxidation of Alcohols. Primary and secondary alcohols can be oxidized to aldehydes and ketones in good yields via treatment with methanesulfonic anhydride and dimethyl sulfoxide in HMPA (eqs 8 and 9). Dichloromethane can be substituted as the solvent, but the use of HMPA leads to cleaner products. Methanesulfonic anhydride works especially weU for the conversion of primary alcohols to aldehydes. Benzylic aldehydes can also be formed using this method. 

The synthesis of key intermediate 12, in optically active form, commences with the resolution of racemic trans-2,3-epoxybutyric acid (27), a substance readily obtained by epoxidation of crotonic acid (26) (see Scheme 5). Treatment of racemic 27 with enantio-merically pure (S)-(-)-1 -a-napthylethylamine affords a 1 1 mixture of diastereomeric ammonium salts which can be resolved by recrystallization from absolute ethanol. Acidification of the resolved diastereomeric ammonium salts with methanesulfonic acid and extraction furnishes both epoxy acid enantiomers in eantiomerically pure form. Because the optical rotation and absolute configuration of one of the antipodes was known, the identity of enantiomerically pure epoxy acid, (+)-27, with the absolute configuration required for a synthesis of erythronolide B, could be confirmed. Sequential treatment of (+)-27 with ethyl chloroformate, excess sodium boro-hydride, and 2-methoxypropene with a trace of phosphorous oxychloride affords protected intermediate 28 in an overall yield of 76%. The action of ethyl chloroformate on carboxylic acid (+)-27 affords a mixed carbonic anhydride which is subsequently reduced by sodium borohydride to a primary alcohol. Protection of the primary hydroxyl group in the form of a mixed ketal is achieved easily with 2-methoxypropene and a catalytic amount of phosphorous oxychloride. 

An example of an alcohol that can undergo rapid skeletal rearrangement is 3,3-dimethyl-2-phenyl-2-butanol (Eq. 29). Attempts to reduce this alcohol in dichloromethane solution with l-naphthyl(phenyl)methylsilane yield only a mixture of the rearranged elimination products 3,3-dimethyl-2-phenyl-l-butene and 2,3-dimethy 1-3-phenyl-1 -butene when trifluoroacetic acid or methanesulfonic acid is used. Use of a 1 1 triflic acid/triflic anhydride mixture with a 50 mol% excess of the silane gives good yields of the unrearranged reduction product 3,3-dimethyl-2-phenylbutane, but also causes extensive decomposition of the silane.126 In contrast, introduction of boron trifluoride gas into a dichloromethane solution of the alcohol and a 10 mol% excess of the silane... 

On another front, the mixture of allylic alcohols 512 and 513 was converted by reaction with methanesulfonic acid anhydride in the presence of triethylamine to a mixture of the corresponding mesylates, which were subjected collectively to methanolysis to afford 514, and none of the allylic ether epimeric at C-3 was isolated. N Debenzylation of 514 followed by a classic Pictet-Spengler cyclization then afforded ( )-buphanisine (361) (208). 

Conversion of alcohols to sulfonate esters is a way of labilising them to nucleophilic substitution and elimination. The common leaving groups are arenesulfonates, particularly p-toluenesulfonate (tosylate), methanesulfonates (mesylate) and trifluromethanesulfonate (triflate) they are introduced by reaction of the acid chlorides (or, in the case of the trifluoromethanesulfonates, acid anhydrides) in a basic solvent such as pyridine. Traditionally, the reactions are carried out in pyridine as solvent, but both this solvent and the liberated... 

Isoindoles can be produced by eliminations from A-substituted isoindolines (1,3-dihydro-isoindoles), themselves readily produced by the reaction of a nitrogen nucleophile and a l,2-bis(bromomethyl)-benzene examples are the pyrolytic eUmination of acetic acid from the cyclic hydroxylamine acetate,or, at a much lower temperature, of benzyl alcohol from an A-hydroxy-isoindoline benzyl ether, or of methanesulfonic acid from a corresponding mesylate. A-substituted isoindoles, too, have generally been made from an isoindoline by elimination processes, thus A-oxides can be made to lose water by pyrolysis," or better, by treatment with acetic anhydride. ... 

The desired sulfonate ester is usually prepared by reaction of the alcohol in pyridine with the appropriate sulfonyl chloride, that is, methanesulfonyl chloride (mesyl chloride) for a mesylate, y)-toluenesulfonyl chloride (tosyl chloride) for a tosylate, or trifluoromethane-sulfonyl chloride [or trifluoromethanesulfonic anhydride (triflic anhydride)] for a triflate. Pyridine (C5H5N, pyr) serves as the solvent and to neutralize the HCI formed. Ethanol, for example, reacts with methanesulfonyl chloride to form ethyl methanesulfonate and with yj-toluenesulfonyl chloride to form ethyl /-toluenesulfonate ... 

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