Synthesis and photophysical properties of novel benzophospholo[3,2-b]indole derivatives

Abstract

The parent benzophospholo[3,2-b]indole was prepared by the reaction of dichlorophenylphosphine with a dilithium intermediate, which was prepared in two steps from 2-ethynyl-N,N-dimethylaniline. Using the obtained benzophosphole-fused indole as a common starting material, simple modifications were carried out at the phosphorus center of the phosphole, synthesizing various functionalized analogs. The X-ray structure analysis of trivalent phosphole and phosphine oxide showed that the fused tetracyclic moieties are planar. The benzophosphole-fused indoles, such as phosphine oxide, phospholium salt, and borane complex, exhibited strong photoluminescence in dichloromethane (Φ = 67–75%).

Alkyne Insertion into P–C(sp2) Bonds as a Route to Fused Phospholes: Transition-Metal-Like Reactivity at Phosphorus

“…This is a new ring system. Related phospholo­[3,2- b ]­indole ,, and phosphindolo­[3,2- b ]­indole , ring systems have been described, but to our knowledge, the simplest phospholo­[3,2- b ]­pyrrole ring has not been previously synthesized. Compound 16 , which is derived from the C3-substituted pyrrolyl precursor 9 , consists of a tungsten pentacarbonyl complex of 1-methyl-4,5,6-triphenylphospholo­[2,3- b ]­pyrrole, which has also not been previously synthesized.…”

“…Fused phospholes have applications as components for optoelectronic materials − and also have been used as ligands for catalytic applications. , As a result, synthetic routes to fused phospholes are of great interest. They are most commonly synthesized via metalation-cyclization ,,, or through transition-metal-catalyzed alkyne annulation reactions. − Other methods applied to their synthesis include Fagan–Nugent Ti mediated cyclization, rearrangement of phosphirenes, intramolecular CH activation by phosphinidene complexes, and photocatalyzed annulation reactions .…”

“…Fused phospholes have applications as components for optoelectronic materials − and also have been used as ligands for catalytic applications. , As a result, synthetic routes to fused phospholes are of great interest. They are most commonly synthesized via metalation-cyclization ,,, or through transition-metal-catalyzed alkyne annulation reactions. − Other methods applied to their synthesis include Fagan–Nugent Ti mediated cyclization, rearrangement of phosphirenes, intramolecular CH activation by phosphinidene complexes, and photocatalyzed annulation reactions . The alkyne annulation reactions, whether metal-mediated or photocatalyzed, offer very efficient routes to benzophospholes; however, regioselectivity remains a challenge, with mixtures of direct and rearranged products resulting.…”

“…H NMR (CDCl 3 ): δ 7.17 (m, 1H, C 4 H 3 S), 7.48−7.39 (m, 3H, Ph), 7.52 (m, 1H, C 4 H 3 S), 7.66−7.55 (m, 2H, Ph), 7.73 (m, 1H, C 4 H 3 S) 13. C NMR (CDCl 3 ): δ 128.7 (d,3 J CP = 12 Hz, C 4 H 3 S), 128.8 (d,3 J CP = 11 Hz, Ph), 129.6 (d, 2 J CP = 15 Hz, Ph), 131.5 (d, 4 J CP = 2 Hz, Ph), 135.1 (d,3 J CP = 5 Hz, C 4 H 3 S), 137.6 (d, 2 J CP = 16 Hz, C 4 H 3 S), 140.1 (d,1 J CP = 39 Hz, ipso-Ph), 141.3 (d,1 J CP = 29 Hz, C 4 H 3 S), 195.9 (d, 2 J CP = 7 Hz,1 J CW = 126 Hz, cis-CO), 198.8 (d, 2 J CP = 32 Hz, trans-CO).b. Synthesis of [W(CO) 5 {PPh(Cl)(2-C 4 H 3 NCH 3 )}] (8) and [W(CO) 5 {PPh(Cl)(3-C 4 H 3 NCH 3 )}] (9).…”

Copper-Catalyzed Direct Oxidative C–H Functionalization of Unactivated Cycloalkanes into Cycloalkyl Benzo[b]phosphole Oxides

“…Phosphorus-containing heterocycles have gained considerable attention from synthetic chemists over the past few decades, owing to their wide applicability in organic synthesis, medicinal chemistry, and material science . Among them, benzo­[ b ]­phosphole derivatives, the phosphorus analogue of indole, have recently received much attention as advanced organic optoelectronic materials due to their unique electronic and photophysical properties . However, synthetic approaches to such promising frameworks are relatively scarce.…”