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Fly-ash:H2O Assisted Aldol Condensation: Effect of Solvents on the Synthesis of Some Aryl (E) 2-propen-1-ones

100%

Thirunarayanan G.

Annales Universitatis Mariae Curie-Skłodowska, sectio AA – Chemia

2012

tom 67

nr 1-2

79-121

Some series of aryl (E) 2-propen-1-ones have been synthesized by Fly-ash:H2O catalyzed aldol condensation of aryl methyl ketones and substituted benzaldehydes at reflux condition in atmospheric pressure. The yields of chalcones are higher than 60%. These chalcones were characterized by their physical constants and spectral data, for known compounds their purities were checked with the physical constants and spectral data earlier published in the literature. The effects of solvents on the product have been studied.

Role of water in determining organic reactivity in aqueous binary solvents

88%

Salmar S. , Järv J. , Tenno T. , Tuulmets A.

Open Chemistry

2012

tom 10

nr 5

1600-1608

Kinetic data for organic reactions in various binary water-organic solvent mixtures were collected and quantitatively analysed in terms of linear-free-energy relationships by using tert-butyl chloride (2-chloro-2-methylpropane) solvolysis as the reference system. Linear similarity plots for these kinetic data were determined for solvent systems ranging from pure water mixtures up to considerable amount of cosolvent, and 161 similarity coefficients were calculated from slopes of these plots. The existence of these linear plots demonstrated that the solvent effects are of some common nature in all analysed reaction mixtures independent of the reaction type and the cosolvent used. Therefore it was concluded that the observed effects could be connected to the specific solvating properties of water, which govern reactivity even in significant dilution of water by an organic cosolvent. This conclusion was supported by the linear interrelationship between the slopes of similarity plots of different reactions, and hydrophobicity parameters log P of the reacting compounds. The relative solvent effects observed in binary water-organic solvent mixtures were for the first time directly related to the structure of reacting compounds. [...]

Solvent-controlled diastereoselectivity in tryptophan-catalyzed Mannich reactions

63%

Valero G. , León C. M. , Moyano A.

Asymmetric Catalysis

2015

tom 2

nr 1

Solvent effects in the L-tryptophan-catalyzed Mannich reaction between hydroxyacetone and glyoxylate imines have been examined. The use of a DMSO/1-butanol (4:1 v/v) mixture as solvent at rt provided the expected Mannich adducts in good yields, high anti-diastereoselectivity (up to 10.3:1 anti/syn ratio) and excellent enantioselectivities (up to >99.9% ee for the anti isomer).