Chiroptical properties and the racemization of pyrene and tetrathiafulvalene-substituted allene: substitution and solvent effects on racemization in tetrathiafulvalenylallene

Dissymmetric 1,3-diphenylallene derivative 3 connected with 4,5-bis(methyl-thio)tetrathiafulvalenyl and 1-pyrenyl substituents was prepared and characterized. The molecular structure was determined by X-ray crystallographic analysis. Optical resolution was accomplished using a recycling chiral HPLC, and its chiroptical properties were examined with optical rotation and electronic circular dichroism (ECD) spectra. The title compound underwent photoracemization under daylight. This behavior was investigated in various solvents and compared with that of 1,3-bis(tetrathiafulvalenyl)allene (bis-TTF-allene) derivative 2. The first-order rate plot of the intensity of the ECD spectra at a given time interval gave the rate of racemization. Mild racemization was observed in polar solvents, whereas a relatively fast rate was obtained in less polar solvents. In addition, the TTF groups of the allene also accelerate the racemization rate. These results suggest that the racemization mechanism occurs via a non-polar diradical structure.

Synthesis of pyrrolidine-fused 1,3-dithiolane oligomers by the cycloaddition of polycyclic dithiolethiones to maleimides and evaluation as mercury(II) indicators

The scandium triflate-catalyzed cycloaddition reaction of polycyclic 1,2-dithiolethiones to maleimides is described. The reaction constitutes an easy approach to linear as well as branched oligomeric cis-fused dihydro[1,3]dithiolo[4,5-c]pyrrole-4,6-dione rings interconnected by 3,5-diylidenethiomorpholine-2,6-dithione or ylidene-6-thioxo[1,2]dithiolo[3,4-b][1,4]thiazin-3-one groups. The presence of highly colored, highly polarized push-pull α,β-unsaturated thione groups in their structures make these compounds sensitive to the presence of mercury(II) cation in organic or mixed organic/aqueous solvents.

Complete stereodivergence in the synthesis of 2-amino-1,3-diols from allenes

Herein, we describe studies to understand how both reagent and substrate control can be effectively employed in the stereodivergent oxidative amination of allenes, with transfer of the axial chirality of an enantioenriched precursor to point chirality in each possible diastereomeric 2-amino-1,3-diol product.

Asymmetric synthesis of heteroaryl atropisomers via a gold-catalyzed cycloisomerization–amination cascade reaction

The chiral gold(i) complex enables enantioselective cycloisomerization–amination of 2-(alkynyl)phenyl boronic acids and diazenes in high yields.

The conversion of allenes to strained three-membered heterocycles

The addition of heteroatoms to an allenic double bond yields strained heterocycles that serve as scaffolds for further useful transformations.