Methanesulfonic acid, with phosphorus

NaNC>3 and cone. H2SC>4 gave 5-chloro I-nitrobenzo[2,l,3]selenadiazole 142 in 90% yield (Equation 7) <2004RJC428>. An improved method for nitration of fluorine-substituted benzo[2,l,3]selenadiazoles was also reported. Treatment of a variety of benzo[2,l,3]selenadiazoles with commercially available 90% nitric acid dissolved in a mixture of methanesulfonic acid and phosphorus pentoxide at room temperature gave 4-nitrobenzo[2,l,3]sclc-nadiazoles in 81-94% yield <2004JHC1023>. The obtained 2,1,3-benzoselenadiazoles were used as precursors to o-phenylenediamines (see Section 6.12.5.8). 

Analogously, 2-ethynyl-2-methylcyclobutanone (24) was obtained in 83% yield from the corresponding alcohol 23 upon treatment with methanesulfonic acid and phosphorus pentoxide in diethyl ether at 25 °C. 

In contrast to phosphorus esters, sulfur esters are usually cleaved at the carbon-oxygen bond with carbon-fluorine bond formation Cleavage of esteri nf methanesulfonic acid, p-toluenesidfonic acid, and especially trifluoromethane-sulfonic acid (tnflic acid) by fluoride ion is the most widely used method for the conversion of hydroxy compounds to fluoro derivatives Potassium fluoride, triethylamine trihydrofluoride, and tetrabutylammonium fluoride are common sources of the fluoride ion For the cleavage of a variety of alkyl mesylates and tosylates with potassium fluoride, polyethylene glycol 400 is a solvent of choice, the yields are limited by solvolysis of the leaving group by the solvent, but this phenomenon is controlled by bulky substituents, either in the sulfonic acid part or in the alcohol part of the ester [42] (equation 29)... 

However, when an electron-withdrawing group, e.g., a trifluoromethyl group, is attached to the anilines this procedure is not applicable. A way to circumvent this problem was enlightened by Glasnov et al. [53] who treated the malondianilide 14 with Eaton s reagent, a 7.7% solution of phosphorus pen-toxide in methanesulfonic acid (a. Scheme 6) [54]. This reaction is, however, sensitive to time, temperature, and concentration. More reactive malondian-... 

A powerful and efficient method for the preparation of poly(ketone)s is the direct polycondensation of dicarboxylic acids with aromatic compounds or of aromatic carboxylic acids using phosphorus pentoxide/methanesulfonic acid (PPMA)16 or polyphosphoric acid (PPA)17 as the condensing agent and solvent. By applying both of these reagents to the synthesis of hexafluoroisopropylidene-unit-containing aromatic poly(ketone)s, various types of poly(ketone)s such as poly(ether ketone) (11), poly(ketone) (12), poly(sulfide ketone) (13), and poly-... 

Methanesulfonyl chloride has been prepared by the chlorination of methyl thiocyanate, S-methylthiourethan, sodium methyl thiosulfate or S-methylisothiuronium sulfate from sodium methanesulfonate by the action of phosphorus penta-chloride, phosphorus oxychloride, or benzotrichloride from methanesulfonic acid by the action of phosphorus pentachloride or by the reaction of methylmagnesium iodide with sulfuryl chloride. ... 

Vinylcyclobutanones may be converted to cyclohex-2-enones 1 on treatment with Eatons reagent (methanesulfonic acid/phosphorus pentoxide).69 The yields are usually only moderate due to a side reaction leading to cyclopentenones. This side reaction is especially important for 2,2-disubstituted cyclobutanones (R3 4 H).69 In all cases the carbonyl group migrates to the /(-position of the double bond. 

The same mode of migration is found if the rc-bond needed for rearrangement is part of an aryl ring in the 2-position. Usually only the substituted C3 of cyclobutanones (Table 5)71 74,140 or cyclobutanols (Table 6)75 migrates on treatment with trifluoroaeetic acid,73 methanesulfonic acid,71 trifluoromethanesulfonie acid, 140/ -toluenesulfonic acid,74 phosphorus pentoxide,71-74 and tin(IV) chloride,72 generally with diethyl ether or benzene as the solvent. 

Only resinous products and methyl 6-acetamidopyridine-3-carboxylate were obtained when methyl 6-aminopyridine-3-carboxylate was reacted with ethyl 2-acetoxyacetoacetate by heating in phosphorus pentoxide, methanesulfonic acid, or polyphosphoric acid in the absence or presence of a solvent such as toluene, xylene, or methylene chloride. However the desired methyl 3-acetoxy-2-methyl-4-oxo-4//-pyrido[ 1,2-a]pyrimidine-7-carboxylate 93 was obtained when the above components were reacted in N, A-dimethylacetamide in the presence of polyphosphoric acid at 100°C for 48 hours (84FES837). 

Another reported synthesis of symmetrical spiro-1,3-dithietanes 163a-d substituted with an adamantyl moiety is based on the [2+2] cycloaddition of two molecules of variously substituted adamantane-2-thiones <1997BCJ509>. With methanesulfonic acid as an acidic catalyst, the reaction provided 1,3-dithietanes 163a-d in high yields at ambient temperature. A similar reaction was performed with phosphorus pentachloride as the catalyst (Equation 22 Table 8) <2002AXCo231>. 

Methoxy-4-oxo-4//- 1-bcnzotellurinh 1.20 g (3.92 mmol) of 2-carboxyethenyl 3-methoxyphenyl tellurium are added to a solution of 1 g of phosphorus pentoxide in 10 ml] of distilled methanesulfonic acid and the resultant mixture is stirred at 20° for 4 h. 250 ml] of saturated aqueous sodium hydrogen carbonate solution are then added dropwise, the mixture is extracted with three 50 ml] portions of dichloromethane, and the combined extracts are dried with anhydrous sodium sulfate, filtered, and concentrated. The residue is recrystallized from methanol yield 0.76 g (67%) m.p.103°. 

The indanone oximes (7) gave the aryl- and alkyl-migrated products (8) and (9) (equation 6), with the proportion of (9) itKteasing with increasing steric demand of arenc substituents at the 4- and 7-positions. Exposure of the ( )-oxime (10) to phosphorus pentoxide and methanesulfonic acid gave the product (11) of migration of the yn-alkyl group, presumably via the (Z)-isomer (equation 7). 

Carboxy-l-organoethen-l-yl tellurium compounds are converted to 4-oxo-4H-1-benzotellurins by treatment with phosphorus pentoxide in methanesulfonic acid ... 

Conventional condensation of 1,2-diaminobenzene 16 with 6-fluoro-3,4-dihydro-2H-chroman-2-carboxylic acid 17 under Phillips conditions or using Eaton s reagent (1 10 mixture of phosphorus pentoxide/methanesulfonic acid) yielded 2-(6-fluorochroman-2-yl)-lff-benzimidazole 18 (Scheme 4) [30]. However, irradiating the reaction mixture containing polyphosphoric acid as a catalyst with microwaves afforded the compoimd 18 in comparable yields in a matter of three minutes [30]. 

Multi-walled carbon nanotubes can be functionalized with PBI via a Friedel-Crafts acylation reaction in a phosphorus pentoxide/methanesulfonic acid medium [23]. The composites have been used as reinforced fillers in 100% acidified poly(hydroxyamino-ether) to prepare mixed composites. The acid-base interaction between the PBI chains attached on multi-walled carbon nanotubes plays a crucial role with regard to good dispersion and effective reinforcement. 

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