Design and synthesis of cinchona-based chiral hyperbranched polymers and their application in asymmetric reactions
作者:Sadia Afrin Chhanda、Shinichi Itsuno
DOI:10.1016/j.tet.2020.131247
日期:2020.6
(MH) coupling reaction. AB2 and A2B-type chiral monomers were prepared from cinchona squaramide derivatives, where A (vinyl) reacted only with B (iodophenyl) under MH reactionconditions. The chiral HBPs obtained by the MH polymerization contained cinchona squaramide moieties and demonstrated excellent diastereoselectivity and enantioselectivity in asymmetricMichael addition reactions of methyl 2-
Synthesis of cinchona squaramide polymers by Yamamoto coupling polymerization and their application in asymmetric Michael reaction
作者:Sadia Afrin Chhanda、Shinichi Itsuno
DOI:10.1016/j.reactfunctpolym.2021.104913
日期:2021.7
chiral polymers were successfully utilized as polymeric catalysts in asymmetricMichael addition reactions. Good to excellent enantioselectivities were observed for different types of asymmetricMichaelreactions. Using the chiral homopolymer catalyst P4, almost perfect diastereoselectivity (>100:1) with 99% ee was obtained for the reaction between methyl 2-oxocyclopentanecarboxylate 25 and trans-β-nitrostyrene
Functionalized proline with double hydrogen bonding potential: highly enantioselective Michael addition of carbonyl compounds to β-nitrostyrenes in brine
synthetic manipulation of S-proline allows access to prolinamides 5–7 as organocatalysts capable of double hydrogen bonding for enantioselectiveMichaeladdition reactions of carbonyl compounds to β-nitrostyrenes. It is shown that prolinamide catalyst 7 leads to addition products with a high diastereo- as well as enantioselectivity. The transition state structure involving the binding of electrophilic
aromatic π–π/C–H···π interactions. In particular, CD measurements of chiral and racemic Ar-BINMOL 2a in solution and the solid state show a strong Cotton effect, which revealed that ampli-fication of chirality was observed because of the formation of a chiral supramolecular oligomer derived from the racemic monomer. To this end, the Ar-BINMOLs were used as supramolecular auxiliaries to mediate the Michael
Asymmetric organocatalytic anthrone additions to activated alkenes
作者:Alex Zea、Andrea-Nekane R. Alba、Natalia Bravo、Albert Moyano、Ramon Rios
DOI:10.1016/j.tet.2011.02.032
日期:2011.4
Asymmetric organocatalyticadditions of anthrones to activated alkenes are discussed. The reaction between anthrone or dithranol and α,β-unsaturated aldehydes is catalyzed by diphenylprolinol trimethylsilyl ether in toluene at −40 °C, giving the Michael adducts with good yields and enantioselectivities. Bifunctional amino-thioureas efficiently catalyze the additions of anthrones to both nitroalkenes and maleimides