One-pot synthesis of helical aromatics: stereoselectivity, stability against racemization, and assignment of absolute configuration assisted by experimental and theoretical circular dichroism.
Helical aromatics (1) were synthesized via one step in good quantity by solvent-free condensation of N,N'-p-phenylenediamine (2) and various carboxylic acids in the presence of a Lewis acid. Microwave irradiation greatly facilitated the condensation reaction to furnish 1 with a 100% diastereo- and a 50% enantioselectivity, when a chiral carboxylic acid was utilized. 1f, derived from 2-methylglutaric acid, was quite stable, no racemization taking place even at 200 degrees C. The assignment of the absolute configurations to the helical aromatics has been achieved by experimental and theoretical CD spectra calculated by time-dependent density functional theory.
Watanabe
Masashi
M
Department of Materials Science, Shizuoka University, Hamamatsu, Shizuoka 432-8561, Japan.
Suzuki
Hiroshi
H
Tanaka
Yasutaka
Y
Ishida
Toshimasa
T
Oshikawa
Tatsuo
T
Tori-I
Akiyoshi
A