Phosphorus pentoxide, in methanesulfonic

Carboxy-l-organoethen-l-yl tellurium compounds are converted to 4-oxo-4H-1-benzotellurins by treatment with phosphorus pentoxide in methanesulfonic acid1. 

Phosphorus pentoxide in methanesulfonic acid has been used as substitute for polyphosphoric acid . N-Tosylimidazole, a new reagent, has been used in sugar chemistry for a clean 2-tosylation and a one-step preparation of anhydrosugars ... 

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°. 

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 the preparation of the linear analogues, solvents such as nitrobenzene [478] and methylene chloride [479] were used. A new method capable of creating poly(ether ketone) and polyfthioether ketone) was recently disclosed by Ueda et al. [480-482]. Here, the dehydrating power of a mixture of phosphorus pentoxide and methanesulfonic acid (MSA) is the driving force for the direct polycondensation of aromatic dicarboxylic acids with aryl compounds contain-... 

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). 

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). 

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. 

Ueda et al. established a modified method for the synthesis of PBOs (Figure 5.25) from 4,4 -oxydibenzoic acid and 3,3 -dihydroxybenzidine-dihydrochloride by using phosphorus pentoxide/ methanesulfonic acid (PPMA) as the condensing agent in place of PPA [54]. 

High lEC and high molecular weight linear SPIs can be easily cross-linked in the presence of phosphorus pentoxide/methanesulfonic acid (PPMA) or phosphorus pentoxide. Two different ways were recently described by Okamoto and his group ... 

Ueda et al. reported that in some cases, PBIs could be synthesized by polymerization of dicarboxyUc acids and tetraamine hydrochloride salts in Eaton s reagent (a solution mixture of phosphorus pentoxide [P2O5] in methanesulfonic acid [MSA] at the weight ratio of P205/MSA= 1/10, it is also denoted as PPM A) [6]. They also... 

---