Tosic

TosOH 4-methylbenzenesulfonic acid = p toluenesiilfonic acid, tosic acid X, Y leaving groups. e.g., halogen, RSOj, in substitution and elimination reactions... 

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

Several groups have used the Paal-Knorr reaction to synthesize trialkylfurans. Ballini prepared a series of 3-alkyl-2,5-dimethylfurans (53) in 60-94% yield by treatment of the corresponding diones (52) with tosic acid. Weirsum produced the sterically congested tri-r-butylfuran 55 from dione 54, but was unable to use the same strategy to furnish the tetra-t-butyl derivative. ... 

Treatment of that intermediate with aluminum chloride leads to selective demethylation of that ether para to the carbonyl group (23). Cyclization by means of tosic acid gives the dihydronaphthalene nucleus (24). Alkylation of the phenol with N-(2-chloroethyl)pyrrolidine affords nafoxidine (25). ... 

Nitromifene (85) is such an agent. A Grignard reaction of aryl ether and ketone leads to tertiary carbinol Tosic acid dehydration leads to a mixture of 1 and stilbenes which constitute the antiestrogen, nitromi fene (85)... 

Removal of the nitro group results in an alteration of antimicrobial spectrum leading to a series of antifungal agents. For example, reaction of 2,4-dichloroacetophenone with glycerol and tosic acid leads to dioxolane Under bromin-... 

Spirapril (37) is a clinically active antihypertensive agent closely related structurally and mechanistically to enalapril. Various syntheses are reported with the synthesis of the substituted proline portion being the key to the methods. This is prepared fkim l-carbobenzyloxy-4-oxopro-line methyl ester (33) by reaction with ethanedithiol and catalytic tosic acid. The product (34) is deprotected with 20% HBr to methyl l,4-dithia-7-azospiro[4.4 nonane-8-carboxylate (35), Condensation of this with N-carbobenzyloxy-L-alanyl-N-hydroxysuccinate leads to the dipeptide ester which is deblocked to 36 by hydrolysis with NaOH and then treatment with 20% HBr. The conclusion of the synthesis of spirapril (37) follows with the standard reductive alkylation [11]. 

Chloroethyl)polystyrenes and (iodoethyl)polystyrenes are each prepared from the alcohol by common reagents in a single step without complications, but one-pot procedures fail to produce completely pure bromide, which must be prepared from the tosylate by assisted halide exchange (57). The preparation of (toluenesulfonyloxyethyl)polystyrene itself, if performed in ice-cold pyridine as for the free analogue (64, 65), required a week to complete (67) if quaternary ammonium and other side-products (68) are to be avoided. In contrast, with non-nucleophilic diisopropylamine (69) as acid acceptor instead of pyridine, (hydroxyethyl)polystyrene and toluene-sulfonyl chloride need only be refluxed in carbon tetrachloride for a few hours to give the desired tosic ester as sole product in quantitative yield (57). 

In much the same vein, acetylation of optically active cf-norgestrel by means of acetic anhydride and tosic acid gives the 17-acetate (72). Reaction with hydroxylamine hydrochloride in pyridine affords the orally active progestin dexnorgestrel acetime (73). ... 

The scheme required to prepare the potent tri-fluoro corticoid cormethasone acetate (292) illustrates the synthetic complexities involved in some of this work. Sequential acetylation of the pregnenolone derivative 278 with first acetic anhydride in pyridine and then acetic anhydride in the presence of tosic acid affords diacetate 279. Reaction of that intermediate with nitrosyl fluoride results initially in addition of the reagent to the 5,6-olefin moiety to afford the fluoro oxime reaction with a second mole of reagent at nitrogen gives the nitroimine derivative 280 passage over alumina serves to hydrolyze the imine function to the corresponding 6-ketone (281). 

As noted previously, a wide variety of aromatic systems serve as nuclei for arylacetic acid antiinflammatory agents. It is thus to be expected that fused heterocycles can also serve the same function. Synthesis of one such agent (64) begins with condensation of indole-3-ethanol (60) with ethyl 3-oxo-caproate (61) in the presence of tosic acid, leading directly to the pyranoindole 63. The reaction may be rationalized by assuming formation of hemiketal 62, as the first step. Cyclization of the carbonium ion... 

A number of new conditions and catalysts have been used for the synthesis of quinazolinones 50 from anthranilic acids, amines and ortho esters, including bismuth trifluoroacetate with an ionic liquid <06TL3561>, lanthanum nitrate or tosic acid under solvent-free conditions at room temperature <06TL4381> and Nafion-H <06SL2507>. 

Hegedus synthesis of ( )-clavicipitic acid //-acetyl methyl ester culminated in the Pd-induced cyclization of 238 to 239, the latter of which was reduced to the target mixture [251], Substrate 238 was prepared via a Heck reaction with the corresponding 4-bromo compound 223 and 2-methyl-3-buten-2-ol (83%). The cyclization also occurs with tosic acid (97%). 

The GC/MS spectra were used to estimate the % depolymerization of TBMS under various conditions (see Table IV). The % depolymerization of polymer samples containing 2-nitrobenzyl tosylate is dependent upon the solvent used to cast films. When xylene is used, a higher % depolymerization is observed than with cyclohexanone. Moreover, the ratio of depolymerization products also varies with casting solvent. Specifically, the indan thermolysis product is more predominant when films were cast from xylene. The reaction with tosic acid hydrate resulted in a high degree of depolymerization this is most likely a consequence of depolymerization occurring during sample preparation. 

---