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

Abstract

Herein, we report a simple and efficient approach to synthesize a functionalized 2,18‐dimethoxy‐5,10,15‐trioxa[9]helicene. It was synthesized from simple phenol building blocks using two subsequent reactions namely oxidative coupling and dehydrative cyclization or palladium mediated cyclization. The molecular integrity of the helical core was determined by single‐crystal X‐ray diffraction and NMR techniques. Its crystal structure showed the spontaneous resolution which was attributed to the conglomerate formation of the same helical isomer via C−H⋅⋅⋅O and π⋅⋅⋅π or H⋅⋅⋅π interactions. Then, it was converted to racemic 2,18‐dihydoxy‐5,10,15‐trioxa[9]helicene. Enantiomers were separated on preparative HPLC with high optical purity (>99 % ee). Based on electronic circular dichroism, the absolute configurations of dextrorotary and levorotatory antipodes were assigned as P and M, respectively. We also studied the absorption, emission and chiroptical behavior of these helical compounds in the solution state.

Ru(II)-Catalyzed Deformylative C–C Activation and Carbene Insertion: Empowering Diversity-Oriented Synthesis of Unsymmetrical Biaryldiols and Heterobiaryl Amino Alcohols

“…From 3 mmol-scale reactions, biaryldiols 3ai and 3ak were isolated in 93 and 91% yields, respectively (Scheme a). The biaryldiols were also readily converted to valuable π-conjugated polycyclic benzofurans 8aj – 8am in high yields, showcasing synthetic utility (Scheme b) …”

Synthesis and Properties of Bis(naphthofuran)‐Fused [7]Helicene Derivatives

“…Therefore, helicenes or their derivatives have received much interest in wide utilization [2] such as chiral ligands for asymmetric catalysis, [3] liquid crystal molecules, [4] chiral rotors, [5] sensing, [6] self‐assembly [7] and organic electronics [8] . Due to the advantage of furan to increase molecular interaction and charge transporting ability, [9] synthesis of oxygen‐containing helicenes including their opto‐electronic applications have been reported in recent years [6,9a,10] …”

Synthesis and Stereochemical Behavior of Dioxa[6]helicene Derivatives

“…We recently reported the synthesis of large oxygen-containing functionalized trioxa [9]helicene from the axially chiral furan derivative. [28] Herein, we present the efficient synthesis of dioxa[6]helicene 4 and its derivatives, attempts at resolution of racemic 4 into enantiomers, single-crystal X-ray analysis of racemic 4, and photophysical properties (UV-Vis absorption, fluorescence, cyclic voltammetry) of dioxa[6]helicene 4 and its derivatives.…”