One‐Pot, Regioselective Consecutive Multihalogenation of 2,2′‐Bithiophene

Abstract

The one‐pot regioselective consecutive multihalogenation of 2,2′‐bithiophene (1) was demonstrated. Compound 1 was consecutively halogenated with lithium halides such as lithium bromide, chloride, and/or iodide in the presence of lead tetraacetate in chloroform at room temperature or under reflux conditions to give 5‐bromo(or chloro)‐5′‐iodo(or chloro)‐, 3‐bromo(or chloro)‐5,5′‐dibromo(or dichloro, diiodo)‐, 3,3′‐dibromo‐(or dichloro)‐5,5′‐diiodo(or dibromo, dichloro)‐, and 3,3′,5‐tribromo(or trichloro)‐5′‐iodo(or bromo)‐2,2′‐bithiophenes. Notably, this process offers a regioselective method for consecutive multihalogenation in one pot, and the yields and selectivity are also higher than those obtained in the step‐by‐step and concurrent halogenation methods.

Engineering the Substitution Position of Diphenylphosphine Oxide at Carbazole for Thermal Stability and High External Quantum Efficiency Above 30% in Blue Phosphorescent Organic Light‐Emitting Diodes

“…The PCPO25 host material was designed to take advantage of the merits of good charge transport properties and low bandgap of substitution at 2-position of carbazole, and high glass transition temperature and high quantum effi ciency of substitution at 4-position of carbazole. [ 14 ] It was reported that substitution of diphenylphosphine oxide at 2-position of carbazole reduced the bandgap and increased charge transport properties because of deepened LUMO level, resulting in low driving voltage and high power effi ciency in blue PHOLEDs. [ 17 ] On the other hand, the substitution of diphenylphosphine oxide at 4-position of carbazole was effective to increase the glass transition temperature and quantum effi ciency of blue PHOLEDs due to steric hindrance and balanced charge density.…”

“…[ 17 ] On the other hand, the substitution of diphenylphosphine oxide at 4-position of carbazole was effective to increase the glass transition temperature and quantum effi ciency of blue PHOLEDs due to steric hindrance and balanced charge density. [ 14 ] Therefore, the substitution of the diphenylphosphine oxide at 2-and 5-positions may have synergic effect on the thermal stability, low driving voltage and high quantum effi ciency.…”

“…[6][7][8][9][10][11] Another method was to substitute the electron transport unit at 2-or 3-positions of carbazole. [12][13][14] The substitution enhanced the electron transport properties of carbazole derivatives, resulting in high quantum effi ciency. The other method was to attach electron transport units at 2,7-or 3,6-positions of carbazole.…”

Structurally Diverse π‐Extended Conjugated Polycarbo‐ and Heterocycles through Pd‐Catalyzed Autotandem Cascades

“…Our initial effort was directed towards thiophene and benzothiophene derivatives that would leadt op olycyclic structures, which are widelyp resenti nf unctional organic materials. [29] Thus, for our study we chose the 3,3'-dibromo-2,2'-bithiophene 17 a [30] and the 3,3'-2,2'-dibenzodithiophene 17 b. [31] Delightfully,t he autotandem cascade reactions with 17 a proceeded as expected to yield spirodithiophenes [32] 18 with moderate to good yields (Scheme 11).…”

A Step-Efficient Pathway to Chlorine-Functionalized Thiophene Oligomers by Palladium-Catalyzed Deprotonative Coupling of Chlorothiophenes

“…Synthesis of 3Dd was carried out as described for the synthesis of 3Aa from 2-chlorothiophene (1d; 2.58 g, 21.8 mmol), TMPMgCl•LiCl (1 M in THF, 26.1 mL, 26.1 mmol), 2-bromothiophene (2D; 2.50 mL, 26.1 mmol) and Pd-PEPPSI-SIPr (0.11 mg, 0.16 mmol) in THF (50 mL) at 60 °C for 24 h. The 1 H NMR spectrum was identical to that reported previously. 18 Yield: 76%; light-yellow solid. 1 H NMR (400 MHz, CDCl 3 ): δ = 6.83 (d, J = 4.1 Hz, 1 H), 6.93 (d, J = 4.1 Hz, 1 H), 7.01 (dd, J = 3.7, 5.0 Hz,1 H), 7.10 (dd, J = 0.9, 3.7 Hz, 1 H), 7.22 (dd, J = 1.4, 5.0 Hz, 1 H).…”