Enantiomerically Pure 5,13‐Dicyano‐9‐oxa[7]helicene: Synthesis and Study

Abstract

Optically pure dicyano oxa[7]helicenes and helicene-like molecules have been prepared and investigated for their optical behavior. The isomers of the intermediate 4,4′-biphen-anthrene-3,3′-diol were resolved by physically separating their 1-menthyl carbonate derivatives. In this work a mild method was developed to cleave ArOMe in presence of a cyano group. The optical rotation of atropisomeric diol, helicenes-like compounds and the oxa[7]helicenes was observed to be in increasing order, while the molecules also showed good response to circularly polarized luminescence.

Synthesis and Study of Photophysical Properties of 6,12‐Dicyano‐9‐oxa[7]helicene

“…Compound 3 had poor solubility in most of the organic solvents, except DMSO. [6] However, the present isomer 4 was found to be readily soluble in many organic solvents, like dichloromethane, chloroform, 1,2-dichloroethane, toluene, chlorobenzene, but and poorly soluble in acetone, ethylacetate, acetonitrile, THF, diethylether and alcohols.…”

“…The stilbene derivative 6 was synthesized from benzaldehyde by Knoevenagel condensation. [6] One of the most commonly employed approaches to construct phenanthrene derivatives involves photochemical oxidative cyclization of corresponding stilbene derivatives. We have developed an effective protocol for such cyclization for the preparation of number of phenanthrene derivatives.…”

“…The cleavage reaction did not proceed in presence of BBr 3 in dichloromethane, [11] gave poor yields with HBr-Acetic acid [12] or LiBr in DMF. [6] Subsequently the reaction proceeded well with AlCl 3 -DMF and hydroxyl derivative 8 was isolated in moderate yield. [13] The homocoupling of 8 proceeded smoothly with the standard reagent of Cu-TMEDA [14] and a single regioisomer of diol 9 was obtained in good yield.…”

“…The crystalliza-tion study was severely hampered by its very poor solubility in most of the common organic solvents. [6] However, we were able to access the enantiomers by physically separating the intermediate diol by making suitable chiral esters. The photophysical and chiroptical properties of 3 were investigated.…”

Synthesis, Chiral Resolution, and Optical Properties of 2,18‐Dihydoxy‐5,10,15‐trioxa[9]helicene

“…Next, to get the target compound 4 , the oxidative homocoupling of 9 was the key step of our synthetic approach. Generally, copper‐based homogeneous catalysts are known to carry out oxidative coupling reactions [8j,l] . Therefore, we subjected oxidative coupling of 9 in the presence of copper complex (prepared in situ from anhydrous CuCl 2 and tetramethylethylenediamine in methanol) to afford dimethoxy‐ 4,4′‐biphenanthryl‐3,3′‐diol ( 10 ) in good yield (yield=69 %, Scheme 2).…”