Methanesulfonic acid anhydride

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). 

Starting Molecule Lysergic acid monohydrate Reagents Methanesulfonic acid anhydride... 

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. 

Trifluoromethanesulfonic anhydride Methanesulfonic acid, tri-fluoro-, anhydride (8, 9) (358-23-6)... 

Nitrophenol Phenol, p-nitro- (8) Phenol, 4-nitro- (9) (100-02-7) Trifluoromethanesulfbnic anhydride Methanesulfonic acid, trifluoro-, anhydride (8,9) (358-23-6)... 

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... 

Compound 102 is used as the building block for the syntheses of PNU-86093 and its analogues, as described in Scheme 21. Namely, the Friedel-Crafts acetylation reaction of 102 under acetic anhydride, methanesulfonic acid, and methanesulfonyl anhydride [51,65] affords compound 103 (PNU-... 

The third procedure illustrated by this preparation involves the reaotion of ketones with trifluoromethanesulfonic anhydride in a solvent such as pentane, methylene chloride, or carbon tetrachloride and in the presence of a base such as pyridine, lutidine, or anhydrous sodium carbonate.7-11,15 This procedure, which presumably involves either acid-catalyzed or base-catalyzed enolization of the ketone followed by acylation of the enol with the acid anhydride, has also been used to prepare other vinyl sulfonate esters such as tosylates12 or methanesulfonates.13... 

Dibutylboron triflate Methanesulfonic acid, trifluoro-, anhydride with dibutylborinic acid (9) (60669-69-4)... 

The 4-amino group of 31 was selectively acetylated under acidic conditions using acetic anhydride (1 equiv.) and methanesulfonic acid (1 equiv.) in acetic acid and f-butylmethyl ether to give 32. Deallylation of 32 using 10% Pd/C in the presence of ethanolamine in refluxing ethanol proceeded as before to afford 1, which was converted to the phosphate salt in 70% yield with high purity (99.7%). The overall yield of 1 from epoxide 23 was 35-38%. 

A reactor was charged with the step 3 product and mixture (64.9 g), methacrylic anhydride (36.0 g), methanesulfonic acid (5.3 g), and 325 ml toluene and then heated to 90°C for 3 hours. The mixture was then added to aqueous and treated with 500 ml of toluene. The organic layer was isolated and then washed with brine and additized with phenothiazine (0.33 g) and then concentrated and 63.2 g of product isolated as a colorless liquid. Analysis indicated it was a mixture of four isomers in an isomeric ratio of Isomer 1 (preferred) Isomer 2 Isomer 3 Isomer 4 of 38 34 17 11, respectively. 

Treatment of salicylic hydrazide in toluene with a single carbon insertion unit, such as carboxylic acid anhydride, acid chloride, and orthoester, in the presence of an equimolecular amount of methanesulfonic acid gave the l,3,4-benzoxadiazepin-5-ones (530) (43-68% yield), via the O-acylation intermediates (529) (92S929). 

Pyrrole- and indole-carboxylic acid chlorides react with dialkyl- and diaryl-cadmium to yield the ketones and it is noteworthy that the reaction of the anhydride of indole-2,3-dicarboxylic acid with diphenylcadmium produces 3-benzoylindole-2-carboxylic acid and not its isomer (53JCS1889). The ability of l-methylindole-2-carboxylic acid to react with nucleophiles is enhanced by conversion into the mixed anhydride with methanesulfonic acid. The mixed anhydride reacts with carbanions derived from diethyl malonate and from methyl acetate to yield the indolyl (3- keto esters (80TL1957). 

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