Ethyl tosyl derivative

A thiol, usually under basic catalysis, can undergo Michael addition to an activated double bond, resulting in protection of the sulfhydryl group as a substituted S-ethyl derivative. Displacement of an ethyl tosylate by thiolate also affords an S-ethyl derivative. 

Phenethyl tosylate solvolyzes in CF3C02H orders of magnitude faster than ethyl tosylate (Figure 2.25). Because the neighboring phenyl ring can make a -electron pair available, a phe-nonium ion intermediate is formed. Phenonium ions are derivatives of the spirooctadienyl... 

TTte A-tosyl derivative of verruculotoxin (294) was prepared by cyclization of the (S),(S)-enantiomer of amino acid 293 on the action of ethyl chloroformate in the presence of A-methylmorpholine (91TL1417). 2-tert-Butylperhydropyrido[l,2-a]pyrazin-3-one was prepared by reacting 2-(N-... 

Ozonolysis of tosyl derivative 295a led to the corresponding protected azonane-3,8-dione in 50% yield (Equation 41). Ruthenium-catalyzed oxidation was found to be more efficient, resulting in an increased 70% yield of the product, which is consistent with the result obtained for dialkyl-substituted systems (Scheme 32, Section 14.10.6.3) <1995J(P1)1137>. Similar ozonolysis of pyrrolo ethyl carboxylate 295c led to 75% of cyclic amino acid derivative <20010L861>. 

Aza Diels-Alder reactions. The p-tol-BINAP ligand is used to promote asymmetric condensation between the IV-tosyl derivative of ethyl glyoxylate and Danishefsky s diene at -78°. 

Polyamine chain extension, 48-56 by acrylamide 51, 52. 53 by aziridine 48,49 by l-bromo-3-chloropropane, 55 by (2-bromoethyl)phthalimide, 51 by 3-bromopropylphthalimide, 53 by chloroacetonitrilc, 51 by chloroacetyl chloride. 50 by lV-(2-chloroethyl)acetamide, 52 by derivatives of chloroacetic acid. 50 by dichloro(o)-bromoalkyl)boranes. 56 by IV-ethylchloroacetamide, 52 by 3-phthalimidopropyl tosylate, 54 by /V-tosyl-2-bromoethylamine, 49 by 2-(N-tosylamino)ethyl tosylate. 49 by Af-tosylaminoacetyl chloride, 50 Polyamino diols. 59 Polyaza-crown macrocycles. 349-367 alkyl-substituted. 364.365 from bis-sulfonamides, 358-361 from diacid dichlorides, 352-357 from diesters, 352-357 from dihalides, 362-366 from diols, 366 from ditosylates. 362-366 Polyaza-crown macrocycles (miscellaneous), table. 392... 

Pyrazoles.—Formation. 3-Amino-4-ethylthio-5-methylpyrazole (311) is formed by the action of hydrazine on the nitrile MeBrC=C(SEt)CN. Acetylenic hydrazones R C=C-C(R )=NNHTos (R = H, Pr, or Ph R = H or Me) cyclize in the presence of potassium carbonate to the pyrazoles (312) via the iV-tosyl derivatives. Treatment of the (p-chlorophenyl)hydrazone (313) of ethyl 2-furylpyruvate with sulphuric acid affords only 10% of the expected ethyl 3-(2-furyl)indole-2-carboxyIate the main product is the pyrazole (314), formed presumably by way of the spiro-intermediate shown. ... 

The solvolysis of trityl derivatives in strongly acidic aqueous media has also been examined. Rates of hydrolysis were correlated to Hr acidity function and theX excess acidity scale. The solvolysis and substitution reactions of 2-(4-methylphenyl)ethyl tosylate have also been studied. " In trifluoroethanobwater (50 50) solution, the corresponding phenonium ion is generated. The kinetics of azide trapping has been studied and compared with results from an analogous system 2-(4-methoxyphenyl)ethyl tosylate. Owing to electronic effects, the methyl-substituted phenonium ion is a more reactive electrophilic species. 

With Af-acyl or Af-sulfonyl hydrazines as nucleophiles, Zincke salts serve as sources of iminopyridinium ylides and ylide precursors.Reaction of the nicotinamide-derived Zincke salt 8 with ethyl hydrazino urethane 42 provided salt 43, while the tosyl hydrazine gave ylide 44 (Scheme 8.4.14). ° Benzoyl hydrazines have also been used in reactions with Zincke salts under similar conditions.Af-amino-1,2,3,6-tetrahydropyridine derivatives such as 47 (Scheme 8.4.15), which showed antiinflammatory activity, are also accessible via this route, with borohydride reduction of the initially formed ylide 46. ... 

An interesting stereochemical situation was found for the lithium-)—)-sparteine complex derived from o-ethyl-A,A-diisopropylcarboxamide 267 (equation 65) . Control experiments, involving lithiodestannylation experiments and the Hoffmann test, led to the conclusion that 268/ep/-268 are configurationally unstable at —78 °C and the e.r. in 269 is determined by a dynamic kinetic resolution of the rapidly interconverting intermediates . It is noteworthy that the configuration is inverted by using tosylates . 

Some difficulty has been encountered with the TV-alkylation (e.g. with ethyl bromoacetate) of 2,3,4,5-tetrahydro-l//-l-benzazepin-5-one (31 R = H) (74JCS(P1)1828). The pharmacological activity (Section 5.16.5) of TV-substituted 5H-dibenz[6,/]azepine and its 10,11-dihydro derivatives has resulted in an intensive study of the TV-alkylation of these ring systems (74CRV101). Generally, alkylation is effected with an alkyl halide or tosylate in the presence of base. Phase transfer TV-alkylations of 5H- dibenz[6,/]azepine have been reported. The method, however, is less successful with the 10,11-dihydro derivatives (79MI51600). 

One Sanofi synthesis of enantiomerically pure (-i-)-clopidogrel (2) utilized optically pure (R)-(2-chloro-phenyl)-hydroxy-acetic acid (20), a mandelic acid derivative, available from a chiral pool. After formation of methyl ester 21, tosylation of (/ )-21 using toluene sulfonyl chloride led to a-tolenesulfonate ester 22. Subsequently, the Sn2 displacement of 22 with thieno[3,2-c]pyridine (8) then constructed (-i-)-clopidogrel (2). Another Sanofi synthesis of enantiomerically pure (-i-)-clopidogrel (2) took advantage of resolution of racemic a-amino acid 23 to access (S)-23. The methyl ester 24 was prepared by treatment of (S)-23 with thionyl chloride and methanol. Subsequent Sn2 displacement of (2-thienyl)-ethyl para-toluene-sulfonate (25) assembled amine 26. 

When acrylonitrile or ethyl acrylate was used as the dipolarophile, the azomethine adducts (134) and (135) were formed no thiocarbonyl ylide addition products were isolable in refluxing toluene or xylene, although the isoindoles (136a) and (136b) derived from them were isolated. In contrast to the reactions with fumaronitrile or AT-phenylmaleimide, the azomethine adducts (134) and (135) were still present at higher reaction temperatures — almost 50% in toluene and 4-5% in xylene. Under the same reaction conditions other electron-deficient dipolarophiles like dimethyl fumarate, norbornene, dimethyl maleate, phenyl isocyanate, phenyl isothiocyanate, benzoyl isothiocyanate, p-tosyl isocyanate and diphenylcyclopropenone failed to undergo cycloaddition to thienopyrrole (13), presumably due to steric interactions (77HC(30)317). 

The TOSMIC anaiog -(tosyl)benzyl isocyanide readily reacts with simple acceptors (ethyl acrylate, acrylonitrile, etc.) to give 4-substituted 2-arylpyrroles. Extension to 2,3-diaryl derivatives by use of styryl acceptors required the use of n-butyllithium as a base. <95SC795>... 

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