The synthesis, structure, and absorption spectra of highly π-frustrated carbo-benzenes with indolic enamine substituents more or less directly conjugated to the C18 macro-aromatic core are described, and their peculiar reactivity is analyzed.

The aldol reaction of acetone with aldehydes in aqueous medium under catalysis by zinc-proline (Zn(L-Pro)2) and secondary amines such as proline, (2S,4R)-4-hydroxyproline (Hyp) and (S)-(+)-1-(2-pyrrolidinomethyl)pyrrolidine (PMP) is shown to proceed by an enamine mechanism, as evidenced by reductive trapping of the iminium intermediate, while the aldol reaction of dihydroxyacetone (DHA) under c...

Chiral pyrrolidinyl-oxazole-carboxamides were synthesized and used as efficient new organocatalysts for the asymmetric Michael addition of ketones with nitroalkenes under solvent-free conditions. Gratifyingly, the corresponding Michael adducts were obtained in higher yields (up to 99%) and excellent stereoselectivities (up to >99/1 dr and 99% ee). Transition state models have been proposed to a...

Kinetic and spectroscopic data indicated that addition of the donor substrate hydroxypyruvate to the thiamin diphosphate (ThDP)dependent enzyme transketolase (TK) led to the accumulation of the -carbanion enamine of ( , -dihydroxyethyl) ThDP, the key reaction intermediate in enzymatic thiamin catalysis. The threedimensional structure of this intermediate trapped in the active site of yeast TK w...

Aldolase antibodies that operate via an enamine mechanism were developed by in vitro selection. Antibody Fab phage display libraries were created where the catalytic active site residues of aldolase antibodies 38C2 and 33F12 were combined with a naive human antibody V gene repertoire. Selection from these libraries with 1,3-diketones covalently trapped the amino groups of reactive lysine residu...

Different enamines were introduced at the meso position of the BODIPY by catalyst free oxidation of tert-amines and in situ cross coupling with 8-chloro BODIPY. The reaction conditions were optimized to achieve better yields. The reaction works well with aliphatic tert-amines bearing an N-(CH-CH-) backbone. The N-alkyl substituents perturb the optical properties of enamine substituted BODIPYs.

Equilibrium constants for keto-enol tautomerisation and migration of hydrogen from carbon to nitrogen to form enamine or zwitterion tautomers have been measured for 2-, 3and 4phenacylpyridines (PyCH,COPh) in aqueous solution at 25 "C. Relative tautomeric stabilities fall in the order ketoimine > enamine > enol and (for the 3-isomer) enol > zwitterion. Values of pKT, (-log KT) where KT = [enamin...

In the title compound, C(21)H(23)N(3)O, the dihedral angles formed by the pyrazolone ring with two phenyl rings are 10.38 (8) and 76.94 (6)°. The sec-butyl-amino group is disordered over two positions, with refined site-occupancy factors of 0.730 (4) and 0.270 (4). The compound could potentially be ligand stabilized in the solid state in a keto-enamine tautomeric form. The amine functionality i...

The dynamic exchange of enamines from secondary amines and enolizable aldehydes has been demonstrated in organic solvents. The enamine exchange with amines was efficiently catalyzed by Bi(OTf)3 and Sc(OTf)3 (2 mol %) and the equilibria (60 mm) could be attained within hours at room temperature. The formed dynamic covalent systems displayed high stabilities in basic environment with <2 % by-prod...

[reaction: see text] Enamine [2 + 2] cycloadditions can be achieved in useful yields simply by stirring a mixture of an aldehyde, diethylamine, a dialkyl fumarate, and potassium carbonate in acetonitrile at 25 degrees C, conditions that are compatible with the presence of a potential leaving group on the beta-position of the intermediate enamine. Methylation and elimination of the product cyclo...