Reagents methanesulfonic acid

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. 

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

A mixture of methanesulfonic acid and P Oj used either neat or diluted with sulfolane or CH2CI2 is a strongly acidic system. It has been used to control the rcgiosclcctivity in cydization of unsymmetrical ketones. Use of the neal reagent favours reaction into the less substituted branch whereas diluted solutions favour the more substituted branch[3]. 

The deterruination of amino acids in proteins requires pretreatment by either acid or alkaline hydrolysis. However, L-tryptophan is decomposed by acid, and the racemi2ation of several amino acids takes place during alkaline hydrolysis. Moreover, it is very difficult to confirm the presence of cysteine in either case. The use of methanesulfonic acid (18) and mercaptoethanesulfonic acid (19) as the protein hydroly2ing reagent to prevent decomposition of L-tryptophan and L-cysteine is recommended. En2ymatic hydrolysis of proteins has been studied (20). 

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-... 

DCC has also been used. The most common catalyst for aliphatic R is concentrated sulfuric acid. The reaction is an equilibrium and is driven to the right by removal of water or by the use of excess reagents. For aromatic R the best catalyst is methanesulfonic acid, which is also used as the solvent. 

Asymmetric reduction of dialkyl ketones. The borohydride 1 reduces dialkyl ketones with low enantioselectivity. However, treatment of the lithium dihydri-doborate 2 with methanesulfonic acid provides Reagent I, which consists of 1 equiv. of R,R-1 and 0.2 equiv. of 2,5-dimethylborolanyl mesylate, which serves as a... 

Classically, Bronsted acids are the promoters of the Fischer glycosylation. Though substrate complexity is still limited in scope, recent developments in these reagents more commonly allows for disaccharide synthesis (Scheme 3.3). For instance, Koto et al. have reported that the combination of methanesulfonic acid (30 mol%) and... 

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-... 

Cyclizations can also be carried out with an esterified oligomer of phosphoric acid called polyphosphate ester. This material is soluble in chloroform.49 (See entries 11 and 12 in Scheme 11.4.) Another reagent of this type is trimethylsilyl polyphosphate.50 Neat methanesulfonic acid is also an effective reagent for intramolecular Friedel-Crafts acylation.51 (See entry 13 in Scheme 11.4.)... 

Silver(I) acetate, 396 Silver hexafluoroantimonate, 467 Silver imidazolate, 467 Silver nitrite-Mercury(II) chloride, 467-468 Silver(l) oxide, 468-469 Silver(II) oxide, 469 Silver perchlorate, 469-470 Silver tetrafluoroborate, 471 Silver(I) trifluoracetate, 471 Simmons-Smith reagent, 210-211, 472, 598 Sinularene, 246 Slaframine, 114, 115 Sodium amalgam, 473-475 Sodium-Ammonia, 472 Sodium benzeneselenoate, 475 Sodium bicarbonate, 476 Sodium bis(methoxyethoxy)aluminum hydride, 93, 476-477 Sodium borate, 322 Sodium borohydride, 477-479, 499 Sodium borohydride-Cobalt(IF) chloride, 479 Sodium borohydride-Methanesulfonic acid,... 

Reduction of amides. Sodium borohydride combined with methanesulfonic acid in DMSO reduces amides to the corresponding amines in 60-90% isolated yield. I he system also reduces acids and esters to primary alcohols. These reductions have been conducted with lithium aluminum hydride and with borane-tetrahydrofurane (5,48),2 hut with somewhat different selectivities. This new reagent, however, appears to be less hazardous than the latter reagent. 

Hydroxylation of arenes.1 Sodium perborate in combination with trifluoro-methanesulfonic acid is an attractive reagent for electrophilic oxidation of arenes to phenols. 

The idea of a spin center shift as an extension of the synthetic scope of the Norrish-Yang reaction was already discussed twice in this chapter. A third example applies to the preparation of six-membered rings. Thus, by treating (3-ketoamides 42 (Sec. 3.4.2.1, Ih) with hypervalent iodine(III) reagents the oc-methanesulfonyloxy-(3-ketoamides 59 are obtained in excellent yields. On irradiation, the 1,5-biradicals 60 are formed, which are converted into the biradicals 61 by elimination of methanesulfonic acid. 

Materials. Sulfolane (99%purity) (Aldrich) was treated with calcium hydride and distilled under reduced pressure. The freshly prepared solvent had a specific conductivity of 1.0 X 10 7 O"1 cm"1 and a residual water content of 8 X 10"3M as determined by Karl Fisher titration. Conductivity water and reagent grade ether (Baker) were used. Glacial acetic acid (CIL), trifluoroacetic acid (Baker), and trifluoro-methanesulfonic acid (3M) were used as received. All these acids had a minimum purity of 99.5% as determined by titration with standard sodium hydroxide. Methanesulfonic acid (Eastman), distilled under reduced pressure, had a purity of 99.6%. Sulfolane solutions of these acids were prepared by weight, and the acid concentrations were checked by acidimetry after the samples were flooded with water. The solutions... 

Dinitroperoxybenzoic acid, (N02>2C6H3C000H. Mol. wt. 228.12, m.p. 113-115°. Caution All peroxyacids are potentially explosive when heated. Prepared by reaction of the carboxylic acid in methanesulfonic acid with 90% H2O2 at 50° (caution The reaction is exothermic at temperatures >53°) yield 93.5%. The reagent is stable for about a year at — 10°. 

Asymmetric Reduction of Ketones. A reagent system consisting of (/ ,/ )-2,5-dimethylborolane (1.0 equiv) and the corresponding borolanyl mesylate (0.2 equiv) reduces a variety of prochiral ketones with asymmetric induction in the range of 80-100% ee. The reagent system is prepared in situ by addition of 1.4 equiv of Methanesulfonic Acid to a solution of the lithium dihydridoborate, prepared as in eq 5 above (eq 7). 

A stronger and more rapid deprotection reagent for Boc groups is made by adding a very low concentration of methanesulfonic acid (MsOH) to TFA.t ... 

Ozone-mediated nitration (Kyodai nitration) of imidazole under neutral condition gave poor yields of 4-nitroimi-dazole. However, the yield improved dramatically with the addition of methanesulfonic acid. The combination NO2-O3 is a much more reactive electrophilic reagent since a reaction temperature of 0°C was sufficient (Scheme 56), <1996JCM244>. The 4-nitro product 238 could also be converted into 1,4-dinitroimidazole 239 over a long period. 

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