PS-TsA

Chemical Designations - Synonyms Methylbenzenesulfonic acid Tosic acid p-TSA Chemical Formula CH3CjH4S03H. 

A synthesis of 2-alkyl-2,3-dihydro-y-pyrones (187) from methoxybutenyne and aldehydes has been described (83TL4551). The condensation of lithiomethoxy-butenyne (184) with aldehydes at -78°C leads to the secondary alcohols 185, which form the dihydropyrones 187 via hydration of the acetylenic bond and hydrolysis of the methoxyethenyl group to the ketoenol 186 (0°C, p-TSA, THF, H2O or 30% HCIO4, 20 min) folowed by intramolecular cycloaddition. 

Polycondensation At room temperature, 0.4% mass of Sn(II) chloride dihydrate (SnCl2-2H20) and 0.4% mass of p-toluenesulfonic acid monohydrate (p-TSA) are introduced into the mixture. The mixture is heated to 180°C under mechanical stirring. The pressure is reduced stepwise to reach 13 mbar, and file reaction is continued for 20 h. The reaction system becomes gradually viscous, and a small amount of L-lactide is formed and refluxed through the reflux condenser. At file end of the reaction, the flask is cooled down, file product is dissolved in chloroform and subsequently precipitated into diethyl ether. The resulting white fibrous solids are filtered and dried under vacuum (average yield 67%). 

When file polymerization is earned out in the same experimental conditions but without addition of p-TSA (S11CI2 2H20 = 0.4% mass, 180°C and 20 h), the resulting polymer is amorphous with Mw = 40,000 and a degree of racemization equal to 75% (determined from 13C NMR measurements). 

A general problem during the syntheses of A9-THC is the formation of the thermodynamically more stable A8-THC, which reduces the yield of A9-THC. It is formed from A9-THC by isomerization under acidic conditions. While the usage of strong acids such as p-TSA or TEA leads mainly to A8-THC, the yield of A9-THC can be increased by employment of weak acids, e.g., oxalic acid [70]. 

Reagents and conditions i, p-TSA, heat ii, n-Bu3SnH, AIBN, heat iii, TiCI4 iv, Me2AICI... 

A novel reaction for the synthesis of 4-amino-substituted quinolines 80 or 4-quinolones 81 was reported. Reaction of various ketones, such as 82 and 83, with o-oxazoline-substituted anilines 84 and 85 in the presence of a catalytic amount of /Mol ucncsul tonic acid (p-TSA) in dry w-butanol led to 80 and 81, respectively <06T9365>. To the authors surprise, the reaction of acetophenones 82 lead to a different outcome than that of the cyclic or acyclic ketones 83 containing more than one carbons a to the ketone. 

Catalysts were "Fascat 4100 a soluble tin catalyst supplied by M T Chemical said to be 95% HgC Sn(0)0H and p-toluenesulfonic acid monohydrate (p-TSA, Lancaster). 

Analogous oligomers were made from dodecanedioic acid (DDA, n=10) and for brassylic acid (BA, n=ll) for comparison studies. Resins made from the oligomeric diols derived from DDA and BA were made into similar coatings in which the diol/HMMM ratio was varied from 68/32 to 53/47 with p-TSA catalyst. The coated panels were baked at 133 °C for 15 min and, in the case of the n = 11 materials at 150 C for 30 min. Results are provided in Tables III and IV. 

Materials. Phthalic anhydride (PA), adipic acid (AA), neopentyl glycol (NPG), p-hydroxybenzoic acid (PHBA), salycilic acid, m-hydroxybenzoic acid (MHBA), xylene, and methyl isobutyl ketone (MIBK) were purchased from Aldrich. p-Toluenesulfonic acid (p-TSA) was purchased from Matheson. "Aromatic 150" solvent and "Resimene 7A6", a hexakis(methyloxymethyl)melamine (HMMM) resin were supplied by Exxon and Monsanto, respectively. "Bonderite 1000" pretreated cold-rolled steel panels 3"x9"x2AGA were purchased from Parker. 

A mixture of the above diol, PHBA, p-TSA and "Aromatic 150" was heated under N2 in a 3-neck flask equipped with stirrer, Dean-Stark trap, condenser and thermometer. The PHBA/diol wt. ratio varied from 20/80 to 60/A0 0.2 wt. % of p-TSA was used. About 10 wt. % of "Aromatic 150" was used the amount was adjusted to maintain the temperature at 230 +/- 3°. Distillate (cloudy H2O) was collected in the Dean-Stark trap during 9 to 11 hr. The reaction mass was cooled to 115°, and MIBK was added to yield a solution (20/80 PHBA/ diol ratio) or dispersion (other PHBA/diol ratios) of the crude polyol. 

Synthesis of a PHBA-benzoic acid adduct. PHBA and benzoic acid in a 1 1.5 mol ratio were heated at 230+/-3° in the presence of 0.2 wt% of p-TSA and "Aromatic 150" as described above. The product mixture was cooled and diluted with an equal volume of a 1 1 mixture of "Aromatic 150" and cyclohexanone. The resulting paste was filtered, dried in an oven, pulverized, washed 5 times with hot water, and dried at 100°. The material was insoluble in hot MIBK. 

Enamel preparation. Solutions or mixtures of polyol, HMMM and p-TSA in a 75/25/0.25 wt. ratio were cast on steel panels and were baked at 175° for the specified time. Dry film thicknesses were 20 to 25 ym. 

Synthesis and characterization of polyols. The procedure described above yields PHBA-modifled oligomers, apparently with minimal side reactions. The odor of phenol was barely detectable in the products, indicating that little phenol had been formed. p-TSA catalyst plays a crucial role. When p-TSA was not used in the 30/70 PHBA/diol reaction only 75% of theoretical distillate was collected, and the product smelled strongly of phenol. Solvent plays an important role by helping control temperature and by facilitating removal of water. If desired, the products can be purified as described to remove small amounts of unreacted PHBA and phenol. 

Direct esterification of PHBA monomer is problematic because the rate of decarboxylation is often comparable to the rate of (co)poly-merlzation (15,16). The problem seems largely overcome by two process refinements introduced here [1] Use of p-TSA apparently catalyzes esterification and more than it catalyzes formation of the undesirable by-product, phenol. [2] "Aromatic 150" solvent helps maintain constant reaction temperature and facilitates water removal. Refluxing solvent also prevents accumulation of sublimed PHBA in the upper parts of the reactor. 

When R2 substituent is flourocontaining alkyl group, the transformation 17 18 becomes hindered and its proceeding requires some special methods. For example, in [48] Biginelli-like cyclocondensations based on three-component treatment of 3-amino-l,2,4-triazole or 5-aminotetrazole with aldehydes and fluorinated 1,3-dicarbonyl compounds were investigated. It was shown that the reaction can directly lead to dihydroazolopyrimidines 20, but in the most cases intermediate tetrahydroderivatives 19 were obtained (Scheme 10). To carry out dehydration reaction, refluxing of tetrahydroderivatives 19 in toluene in the presence of p-TSA with removal of the liberated water by azeotropic distillation was used. The same situation was observed for the linear reaction proceeding via the formation of unsaturated esters 21. 

The first positive results in the synthesis of these heterocyclic compounds by MCR of aminoazoles, aldehydes, and barbituric acids were published in 2008 by Shi et al. [111]. They also used green chemistry methodology and carried out treatment of the starting materials in water under microwave irradiation. The temperature optimization procedure and search for the best catalytic system allowed selecting one equivalent of p-TSA and 140°C as optimum conditions for the synthesis. With application of the procedure elaborated 24 novel pyrazolopyr-idopyrimidines 76 were generated (Scheme 33). 

Cherkupally SR, Mekala R (2008) P-TSA catalyzed facile and efficient synthesis of polyhydroquinoline derivatives through Hantzsch multi-component condensation. Chem Pharm Bull 56 1002-1004... 

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