Asymmetric Diels-Alder reaction was achieved under achiral conditions. Reaction of prochiral 2-methylfuran and N-phenylmaleimide in heptane or hexane solution at 80 °C efficiently gave a conglomerate crystal of exo-type Diels-Alder adduct selectively, and continuous suspension of the reaction mixture with glass beads promoted attrition-enhanced deracemization, leading to an optically active exo-adduct in 90% ee.

Optically active materials could be generated by simple solidification of achiral materials without an external chiral source. When achiral cis-3,4-diphenylsuccinimides were solidified in the presence of a catalytic amount of DBU by evaporating the solvent with stirring, optically active trans-3,4-diphenylsuccinimides were obtained quantitatively with high enantiomeric excesses.

The irradiation of chromone-2-carboxylic esters resulted in the stereo- and regioselective formation of C(2) chiral anti-HH dimers from the triplet excited state. On the contrary, photolysis in the solid-state gave anti-HT dimers exclusively controlled by molecular arrangement in the crystal.

X-Ray crystallographic analysis of N-(1-naphthyl)-2(1H)-pyrimidinethione revealed that the space group was tetragonal and chiral P4(3). The rate of racemization due to the C-N bond rotation was considerably influenced by the solvent properties. A nonpolar solvent lowers the ΔG(‡)value by about 3.0 kcal mol(-1) relative to the value in a polar or a protic solvent. The crystallization of racemic axially chiral pyrimidinethione at high temperature led to the chiral breaking of symmetry up to 91% ee.

ABSTRACT:A novel aromatic diamine 2,3-di(3-aminophenyl)quinoxaline (DAPQ) was prepared from benzil through three steps. New aromatic polyamides were synthesized by the direct polycondensation of DAPQ and several aromatic dicarboxylic acids. The polyamides were obtained almost quantitatively. The inherent viscosities ranged from 0.49 to 0.56dl g-1 .The glass transition temperatures (T.s) of the polyamides ranged from 258 to 291 °C, and the temperatures at 10% weight loss (Td 10 s) ranged between 515 and 546°C. Novel aromatic polyimides were synthesized by the ring-opening polyaddition of several aromatic tetracarboxylic dianhydrides to DAPQ, followed by thermal cyclodehydration. The polyamic acids indicated the inherent viscosities of 0.28-1.13 dlg-1 . T.s of the polyimides ranged between 263 and 298°C, and Td 10s were above 550°C. The polyamides and polyimides were soluble in several organic solvents such as m-cresol.