- Mechanistic Studies on Thiazolidine Formation in Aldehyde/Cysteamine Model Systems
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A mechanism was proposed to elucidate the formation of a thiazolidine in aldehyde/cysteamine model systems. Buffer dramatically promotes thiazolidine formation from formaldehyde and cysteamine. Phosphate tends to stabilize the primary carbocation formed, and this may lead to completion of the cyclization by attack of the amino nitrogen on the activated carbon. Protic solvent, by removing the water molecule, further enhances thiazolidine formation. Redox reaction catalyzed by phosphate ions results in the conversion of thiazolidine to the corresponding thiazoline through hydride transfer.
- Huang, Tzou-Chi,Huang, Lee-Zen,Ho, Chi-Tang
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- Additive-free pd-catalyzed α-allylation of imine-containing heterocycles
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An additive-free Pd-catalyzed α-allylation of different imino-group-ontaining heterocycles is reported. The activation of α-CH pronucleophiles (pKa (DMSO) > 25) occurs without the addition of strong bases or Lewis acids using only the Pd/Xantphos catalyst system. The reaction scope has been studied for various 5- and 6-membered nitrogen-containing heterocycles (yields up to 96%). Mechanistic investigations suggest an initial allylation of the imine-N followed by a Pd-catalyzed formal aza-Claisen rearrangement.
- Kljajic, Marko,Puschnig, Johannes G.,Weber, Hansj?rg,Breinbauer, Rolf
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supporting information
p. 126 - 129
(2017/11/27)
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- A general method for the synthesis of the most powerful naturally?occurring Maillard flavors
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The natural flavors 2-acetyl-1-pyrroline 1a, 2-propionyl-1-pyrroline 1b, 2-acetyl-3,4,5,6-tetrahydropyridine 1c, 2-acetyl-2-thiazoline 1d, 2-propionyl-2-thiazoline 1e, and the artificial flavor 2-acetyl-5,6-dihydro-4H-1,3-thiazine 1f have been prepared by catalytic SeO2 oxidation of the corresponding cyclic imines 6a-c and sulfur cyclic imines 7a-c using TBHP as co-oxidant. The oxidation of the pyrrolines 1a and b is completely regioselective. Professional olfactory evaluation together with the odor threshold of the new flavor 1f is reported.
- Fuganti, Claudio,Gatti, Francesco G.,Serra, Stefano
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p. 4762 - 4767
(2007/10/03)
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- Generation of cyclic ketene-N,X-acetals (X = O, S) from 2-alkyl-1,3-oxazolines and 2-alkyl-1,3-thiazolines. Reactions with acid chlorides, 1,3-diacid chlorides and N-(chlorocarbonyl) isocyanate
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2-Alkyl-1,3-oxazolines, 2-alkyl-1,3-thiazolines, and the corresponding cyclic ketene-N,X-acetals (X = O, S) derived from them were reacted with monoacid chlorides, diacid chlorides, triacid chlorides. A series of these carbon-carbon bond-forming reactions and cyclizations to both substituted 2,3-dihydrooxazolo[3,2-a]pyridine-5,7-diones and 2,3-dihydrothiazolo[3,2-a] pyridine-5,7-diones proceeded under mild reaction conditions. Cyclic ketene-N,X-acetal intermediates play important roles in all these reactions. Related cyclizations with N-(chlorocarbonyl) isocyanate formed substituted 2,3-dihydrooxazolo[3,2-c]pyrimidine-5,7-diones and 2,3-dihydrothiazolo[3,2-c] pyrimidine-5,7-diones. Georg Thieme Verlag Stuttgart.
- Zhou, Aihua,Pittman Jr., Charles U.
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- Research on radioprotective agents: Δ-2 Thiazolines and homologous derivatives
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Compounds derived from Δ-2 thiazoline, Δ-2 thiazolinium iodoalkylate and 4,5-dihydro-1,3 thiazine have been prepared and evaluated as potential antiradiation agents in mice. They generally have a low toxicity and significant radioprotective activity.
- Robbe,Fernandez,Chapat,et al.
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