The first total synthesis of (R)-convolutamydine A

The first total synthesis of (R)-convolutamydine A has been achieved by the organocatalytic addition of acetone to 4,6-dibromoisatin. The absolute configuration was determined by single crystal X-ray diffraction. DFT studies were used to model the transition states for the aldol reaction and equilibrium geometries of the post-aldol reaction intermediates. The DFT study revealed that the aldol bond forming reaction was considerably endothermic.     

Stereoselective Michael Addition of Carbonyl Compounds to ( E )-β-Nitrostyrene Catalysed by N -Toluensulfonyl-l -proline Amide in Ionic Liquids

Summary. N-Toluensulfonyl-l-prolin amide was tested as catalyst in the enantioselective Michael addition of carbonyl compounds to (E)-β-nitrostyrene in nine ionic liquids under different reaction conditions. The reaction rates and enantioselectivities were strongly dependent on the ionic liquids. Change of enantioselectivity was observed too and it is attributed to both the cation and the anion of ionic liquid. The best yields (up to 98%) and enantioselectivity (70% ee) of product were obtained in a basic ionic liquid [bmim]BF₄ at room temperature.     

An enantioselective Michael addition of malonate to nitroalkenes catalyzed by low loading demethylquinine salts in water

An enantioselective Michael addition of malonate to nitroalkenes is efficiently catalyzed by low loading demethylquinine salts in water; the yield range from 49% to 93% and the ee up to 90%.     

New catalytic effect of thiourea on the oxidative cyanation of N-aryltetrahydroisoquinolines

Thiourea itself has been introduced as a mild and efficient organocatalyst for the oxidative α -cyanation of N-aryltetrahydroisoquinolines (THIQs) with trimethylsilyl cyanide (TMSCN), giving the corresponding products in good to excellent yields. Experimental investigations demonstrated that thiourea acts as a radical initiator by abstracting hydroxyl radical (OH) from tert-butyl hydroperoxide (TBHP) directly instead of non-covalent hydrogen bondings (H-bondings) activation. The use of thiourea as a radical initiator offers a new avenue for innovative chemical transformations in organocatalyzed radical chemistry.     

New efficient organocatalytic oxidation of benzylic compounds by molecular oxygen under mild conditions

Efficient aerobic oxidation of benzylic compounds has been achieved under no irradiation using a new organocatalytic system in the presence of acridine yellow and N-hydroxyphthalimide with assistance of a catalytic amount of molecular bromine. Various substrates, especially alkylaromatics, were effectively oxygenated to the corresponding carbonyl compounds with molecular oxygen as oxidant under mild conditions. For instance, indan was oxidized with 92% conversion and 79% selectivity for 1-indanone under 0.3 MPa of O₂ at 75 °C.     

Efficient and mild benzoin condensation reaction catalyzed by simple 1-N-alkyl-3-methylimidazolium salts

The benzoin reaction, catalyzed by simple 1-N-alkyl-3-methylimidazolium salt-based ionic liquid via carbene intermediate, to give the α-hydroxyl ketone proceeds in CH₂Cl₂ under mild conditions.     

Direct organocatalytic in situ generation of novel push-pull dienamines: application in tandem Claisen-Schmidt/iso-aromatization reactions

A new, green, regioselective, one-step, tandem reaction of an aldehyde possessing a non-enolizable carbonyl function with a highly substituted cyclohex-2-enone, under amine catalysis afforded highly substituted phenols or 2-arylidenecyclohexanones, respectively. The yields and regioselectivities were good. Evidence for a pathway involving formation of novel push-pull dienamines is presented along with examples demonstrating the amenability of the process to combinatorial chemistry.     

Mild and efficient deprotection of the amine protecting p-methoxyphenyl (PMP) group

Mild and efficient procedures for deprotection of the amine nitrogen protecting p-methoxyphenyl (PMP) group are described. Periodic acid and trichloroisocyanuric acid (TCCA) were found to be particularly effective in realizing amine liberation using 1 and 0.5 equiv of the oxidant, respectively. Extension of the periodic acid-mediated conditions to simultaneous alcohol oxidation by combination with a catalytic amount of sodium dichromate led to smooth conversion of PMP-protected Mannich products into the corresponding β-amino acids in a one-pot procedure.     

A novel and green protocol for two-carbon homologation: a direct amino acid/K2CO3-catalyzed four-component reaction of aldehydes, active methylenes, Hantzsch esters and alkyl halides

A novel and green approach for the two-carbon homologation of aldehydes using amino acid catalysis has been developed and further extended to the generation of pharmaceutically active cyano-esters via four-component reactions in one-pot.     

An acid-free Pictet–Spengler reaction using deep eutectic solvents (DES)

Deep eutectic solvents (such as the combination of either urea or glycerol with choline chloride) are effective solvents/organocatalysts for Pictet–Spengler condensations to form carbolines. The reaction conditions are quite mild and do not require additional Bronsted or Lewis acid catalyst. Given the inexpensive, non-toxic, and recyclable nature of the DES, these reaction conditions are simple and highly environmentally friendly.