An Efficient Synthesis of Functionalized Helicenes

Abstract

5]-and [6]helicenebisquinones can be prepared easily and in quantity by combining enol ethers of 1,4-diacetylbenzene or 2,7-diacetylnaphthalene with p-benzoquinone. Similar diethenyl aromatics that either have no ether functions or have them attached not to the double bonds, but to the aromatic rings, give the corresponding helicenes in only low yields and low purities.[6]Helicenebisquinone 11c is resolved into its enantiomers. An X-ray diffraction analysis of the adduct of one of these enantiomers and L-prolinol shows the absolute stereochemistry of 11c and the regiochemistry with which the amine adds to the quinone.

Heliphenes and Related Structures

“…Syntheses of [6]-, [7]-, [8]-, and [9] heliphenes have been reported by Vollhardt and coworkers [55,58], and theoretical considerations by Mezey and coworkers [24]. The present paper discusses structures that could be derived from heliphenes and may constitute the object of future synthetic efforts.…”

“…[n]Helicenes are benzenoid hydrocarbons with fascinating properties [7][8][9][10], including enormous values for their specific rotation. For [n]helicenes, a plot of specific rotation versus n has two humps and has a "maximum chirality" at n = 14 [11].…”

“…The resolution of [7]-, [8]-, and [9 ]helicenes was originally performed by Martin and coworkers using Pasteur's laborious method of picking out single crystals, dissolving them, and looking at their optical rotation [14,15]. Since then many other and more efficient synthetic methods have been developed [7,16], including photocyclizations of cis-stilbene derivatives with circularly polarized light providing optically active compounds [17,18].…”

Theoretical Investigation of the Second‐Order Nonlinear Optical Properties of Helical Pyridine–Pyrimidine Oligomers

“…The design of nonbiological structures often relies on the molecular self-organization of superstructures [9] and focuses principally on applications in nanotechnology, optics, and electronics. [10][11][12] Among these systems, conjugated helical molecules composed of ortho-fused aromatic rings, called (homo-or hetero-) helicenes, have been extensively studied, both experimentally [13][14][15][16][17][18] and theoretically. [19][20][21] In particular, strategies have been proposed to enhance their secondorder NLO responses.…”

Domino Friedel–Crafts‐Type Cyclizations of Difluoroalkenes Promoted by the α‐Cation‐Stabilizing Effect of Fluorine: An Efficient Method for Synthesizing Angular PAHs

“…Synthetic methods for helicenes amenable to scale-up-based on the construction of benzene rings by use of Diels-Alder reactions, [27] radical cyclizations, [28] ring-closing metathesis, [29] or CÀH arylation [30] as key steps [31,32] -have recently been developed. In contrast with these reactions, [2 + 2 + 2] cycloisomerizations of triynes [33] can construct three benzene rings in a single operation.…”