Synthesis, Tautomerism, Catalysis

A large-scale, robust enantioselective synthesis of /i-subs(.Hu(.cd-/i-amino esters from aldehydes via imine formation with a chiral amme has been reported.21 

A wide range of kinetic and thermodynamic parameters have been measured for the formation and hydrolysis of Schiff bases derived from pyridoxal S -phosphalc and L-tryptophan over a range of pH and temperature.22 

In a study of imine formation from aldehydes in aqueous solution, formation constants have been correlated with three parameters the pK.d and HOMO energy of the amine and the LUMO energy of the aldehyde.23 

Sodium dodecyl sulfate micelles accelerate condensations of p-di methyl aminocin-namaldehyde with a range of substituted anilines.24 

Indolizidines have been prepared by cyclization of trimethylsilylmethylenecyclo-propylimines.25 

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Jap-KIingermarm reactions, 4, 301 oxidation, 4, 299 reactions, 4, 299 synthesis, 4, 362 tautomerism, 4, 38, 200 Indole, 5-amino-synthesis, 4, 341 Indole, C-amino-oxidation, 4, 299 tautomerism, 4, 298 Indole, 3-(2-aminobutyl)-as antidepressant, 4, 371 Indole, (2-aminoethyl)-synthesis, 4, 278 Indole, 3-(2-aminoethyl)-synthesis, 4, 337 Indole, aminomethyl-reactions, 4, 71 Indole, 4-aminomethyl-synthesis, 4, 150 Indole, (aminovinyl)-synthesis, 4, 286 Indole, 1-aroyl-oxidation, 4, 57 oxidative dimerization catalysis by Pd(II) salts, 4, 252 Indole, 1-aroyloxy-rearrangement, 4, 244 Indole, 2-aryl-nitration, 4, 211 nitrosation, 4, 210 synthesis, 4, 324 Indole, 3-(arylazo)-rearrangement, 4, 301 Indole, 3-(arylthio)-synthesis, 4, 368 Indole, 3-azophenyl-nitration, 4, 49 Indole, 1-benzenesulfonyl-by lithiation, 4, 238 Indole, 1-benzoyl photosensitized reactions with methyl acrylate, 4, 268 Indole, 3-benzoyl-l,2-dimethyl-reactions... 

A new synthesis of arylmethylene- and arylmethine-pyrroles [25 R = CH2C6H4X and CH(C02H)CH2Y] uses 2,5-dimethoxytetrahydrofuran (26). The reaction is subject to acid-base catalysis, and is typically successful only in solvent mixtures of such character, e.g. acetic acid-pyridine. A mechanistic investigation has identified a number of iminium ion intermediates [e.g. tautomerism (27a) (27b)] to explain by-products in particular cases. 

Oxidative processes using mild oxidants (e.g., HgO or Mn02) leading to NN bond formation convert /k-hydrazones 538 into the 1-amino-l,2,3-triazole derivatives 539 (Scheme 242) <1967TL3295, 1971JPR882>. A regioselective synthesis of 2,4-disubstituted 1,2,3-triazoles is based on a reaction of aminoacetophenones 540 with hydrazines (Scheme 243) . The reaction with methylhydrazine proceeds well without any catalysis, but that with phenylhydrazine requires cupric chloride as a catalyst. It is assumed that hydrazone 541 that forms in the first step is in a tautomeric equilibrium with its azo form 542 <2003SC3513>. 

Some insight into the nature of these catalyzed cyclizations is provided by the synthesis of benzobicyclo[3.1.0]hexene 17. Intramolecular cycloaddition under base catalysis (from the tosylhydrazone 14) or by heating compound 18 gave the [3.3.0] bicyclic product 16 but, in the boron trifluoride catalyzed reaction, the [3.2.1] bicyclic product 13 was formed. In the base-catalyzed reaction the intermediate 4,5-dihydro-3//-pyrazole 16 suffered tautomerization (to give 19). The diazo compound 13 cannot tautomerize, and gave a quantitative yield of benzobicyclohexene 17 when heated. These boron trifluoride catalyzed addition reactions do not involve the free diazo compound and in this particular case the cyclic A -tosyl intermediate 12 could be isolated from the reaction mixture. ... 

Inspired by the success of intramolecular addition and tautomerization of aldehydes with a pendant alkyne through cooperative catalysis of a secondary amine and an An complex, in 2008, Yang et al. reported a cascade reaction with the combination of a copper complex and an achiral secondary amine catalyst for the synthesis of attractive carbocycles [48]. This chemistry merged a pyrrolidine-promoted Michael addition via iminium ion intermediates and a Cu-catalyzed cycloisomerization protocol (Scheme 9.54). Various ketones and alkyne-tethered active methylene compounds could be converted into densely functionalized cyclopentene derivatives. Although the asymmetric version was not given, the chemistry described here was amenable for the implementation of asymmetric synthesis of such functionalized molecules by a combination of chiral amines and suitable Au complexes. 

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