Functionalization at Nonperipheral Positions of Triazatruxene: Modular Construction of 1,6,11-Triarylated-Triazatruxenes for Potentially Organic Electronics and Optoelectronics

Abstract

Functionalization from nonperipheral positions of triazatruxene is representing a challenge. Triarylation of the nonperipheral positions (1, 6, and 11) in triazatruxene scaffold has been achieved for the first time via two approaches. The transformations involve arylation/cyclotrimerization and cyclotrimerization/arylation sequences. POCl3-mediated direct cyclotrimerization of oxindoles containing electron-deficient substituents on the aryl group at the C7-position resulted in the formation of 2-chloroindoles, whereas oxindoles containing electron-donating substituents gave the triazatruxenes. Furthermore, desired triazatruxenes were achieved through cyclotrimerization of 7-bromooxindole followed by coupling with arylboronic acids. NMR structural analysis exhibited that two of the suitably substituted oxindole and triazatuxene may have atropisomerism at room temperature. As a representative triazatruxene scaffold, the optoelectronic properties of 9a have also been studied via ultraviolet–visible (UV–vis) absorption spectra and fluorescence spectra of 9a thin films. Also, density functional theory calculation was realized to get knowledge about frontier molecular orbitals. In the light of the information obtained, an organic light-emitting diode (OLED) device utilizing 9a as an emissive layer was applied to obtain white emission. In brief, this study provides the first examples of the synthesis of triazatruxenes bearing aryl substituents at the nonperipheral positions as candidate compounds for organic electronics, optoelectronics, and material chemistry.

Solvent-Mediated Tunable Regiodivergent C6- and N1-Alkylations of 2,3-Disubstituted Indoles with p-Quinone Methides

“…Initially, the retro -Friedel–Crafts alkylation of 3ad was attempted with AlCl 3 as a tert -butyl acceptor in toluene/nitromethane to afford the corresponding para -substituted phenol 5 in 78% yield (Scheme a) . Subsequently, bromo-substituted C6-alkylated product 3ad was explored for cross-coupling reaction with thiophene-2-boronic acid ( 6 ) in the presence of Pd(PPh 3 ) 4 , Na 2 CO 3 , and 1,2-dimethoxyethane:water (2:1), which afforded the corresponding product 7 with 85% yield (Scheme b) . Finally, to demonstrate the applicability of our strategy to the late-stage functionalization of a medicinal relevant molecule, we subjected a pharmaceutically relevant drug to our C6-alkylation protocol: an NSAID indomethacin could be decorated with diarylmethane moieties ( 8d , 8f , and 8k ) with 82–89% yields (Scheme c).…”

Directed C–H Functionalization of C3-Aldehyde, Ketone, and Acid/Ester-Substituted Free (NH) Indoles with Iodoarenes via a Palladium Catalyst System

“…Besides C–H arylation on the C4-position of the indole ring, the bromine group on the 7-position of 5ca has a potential derivatization site. The classical palladium-catalyzed Suzuki–Miyaura coupling of 5ca with thiophene-2-boronic acid provided 13 in excellent yield (89%) (Scheme d) . Pityiacitrin ( 14 ) is a 1-indolyl-β-carboline alkaloid isolated from various sources and has also been tested for various biological activities .…”

“…The classical palladium-catalyzed Suzuki–Miyaura coupling of 5ca with thiophene-2-boronic acid provided 13 in excellent yield (89%) ( Scheme 6 d). 31 Pityiacitrin ( 14 ) is a 1-indolyl-β-carboline alkaloid isolated from various sources and has also been tested for various biological activities. 32 To demonstrate utility in the synthesis of the functionalized natural product of C4-arylated acetylindoles, the synthesis of the substituted pityiacitrin starting from 9ad was carried out successfully ( Scheme 6 e).…”

“…Cross-Coupling of 2-Thienyl Boronic Acid and 5ca. 31 1-(4-Phenyl-7-(thiophen-2-yl)-1H-indol-2-yl)ethan-1-one (13). To a solution of 1-(7-bromo-4-phenyl-1H-indol-2-yl)ethan-1-one (5ca, 63 mg, 0.2 mmol) and thiophen-2-ylboronic acid (31 mg, 0.24 mmol, 1.2 equiv) in DME/water (15 mL, 2:1 v/v, 0.013 M for 5ca) was added Na 2 CO 3 (42 mg, 0.4 mmol, 2 equiv).…”

Solvent-controlled regioselective C(5)–H/N(1)–H bond alkylations of indolines and C(6)–H bond alkylations of 1,2,3,4-tetrahydroquinolines with para-quinone methides

“…The selected C5-alkylated products 7ad-ae and 11 were treated with AlCl 3 in toluene/nitromethane as a tert-butyl acceptor to deliver the corresponding para-substituted phenols 12, 13a, and 13b in excellent yields (Scheme 8a). 24 Furthermore, bromo-phenol 13b was also coupled with 4-biphenylboronic (10) to give 12 in 90% yield (Scheme 8a). The scale-up synthesis of 3aa was also performed to reveal the scalability of the C5-alkylation protocol.…”