42348-04-9Relevant articles and documents
Synthesis of (E)-α,β-unsaturated carboxylic esters derivatives from cyanoacetic acid via promiscuous enzyme-promoted cascade esterification/Knoevenagel reaction
Wilk, Monika,Trzepizur, Damian,Koszelewski, Dominik,Brodzka, Anna,Ostaszewski, Ryszard
, (2019/02/25)
A new enzymatic protocol based on lipase-catalyzed cascade toward (E)-α,β-unsaturated carboxylic esters is presented. The proposed methodology consists of elementary organic processes starting from acetals and cyanoacetic acid leading to the formation of desired products in a cascade sequence. The combination of enzyme promiscuous abilities gives a new opportunity to synthesize complex molecules in the one-pot procedure. Results of studies on the influence of an enzyme type, solvent, and temperature on the cascade reaction course are reported. The presented methodology provides meaningful qualities such as significantly simplified process, excellent E-selectivity of obtained products and recycling of a biocatalyst.
Synthetic and mechanistic studies of metal-free transfer hydrogenations applying polarized olefins as hydrogen acceptors and amine borane adducts as hydrogen donors
Yang, Xianghua,Fox, Thomas,Berke, Heinz
experimental part, p. 852 - 860 (2012/02/05)
Metal-free transfer hydrogenation of polarized olefins (RR′ CCEE′: R, R′ = H or organyl, E, E′ = CN or CO2Me) using amine borane adducts RR′NH-BH3 (R = R′ = H, AB; R = Me, R′ = H, MAB; R = tBu, R′ = H, tBAB; R = R′ = Me, DMAB) as hydrogen donors, were studied by means of in situ NMR spectroscopy. Deuterium kinetic isotope effects and the traced hydroboration intermediate revealed that the double H transfer process occurred regio-specifically in two steps with hydride before proton transfer characteristics. Studies on substituent effects and Hammett correlation indicated that the rate determining step of the HN transfer is in agreement with a concerted transition state. The very reactive intermediate [NH2BH2] generated from AB was trapped by addition of cyclohexene into the reaction mixture forming Cy2BNH2. The final product borazine (BHNH)3 is assumed to be formed by dehydrocoupling of [NH2BH2] or its solvent stabilized derivative [NH2BH2]-(solvent), rather than by dehydrogenation of cyclotriborazane (BH2NH 2)3 which is the trimerization product of [NH 2BH2].
Novel, efficient, and green procedure for the Knoevenagel condensation catalyzed by diammonium hydrogen phosphate in water
Balalaie, Saeed,Bararjanian, Morteza,Hekmat, Shohreh,Salehi, Peyman
, p. 2549 - 2557 (2007/10/03)
Knoevenagel condensation of various aromatic and heteroaromatic aldehydes with active methylene compounds like methyl and ethyl cyanoacetate, malononitrile, and cyanoacetamide proceeds smoothly with stirring in water in the presence of 4 mol% of diammoniu