3d metallaelectrocatalysis for resource economical syntheses

This review summarizes key developments in 3d metallaelectrocatalysis in the context of resource economy in molecular syntheses

High performance non-doped green organic light emitting diode via delayed fluorescence

P. G. thanks the Science & Engineering Research Board (SERB), India, for the Start-up Research Grant (SRG) (Grant No: SRG/2020/000161). E.Z-C. thanks the Engineering and Physical Sciences Research Council (EPSRC) EP/P010482/1 for support. P. R. thanks the Indian Institute of Science (IISc) for generous financial support and the Science & Engineering Research Board (SERB), India, for the SERB-Power Grant (SPG) (Grant No: SPG/2020/000107). B.S. thank IISc for the C. V. Raman Fellowship under the Institute of Eminence (IoE).Non-doped, delayed fluorescence organic light-emitting diodes (OLEDs) provide a route to high performance devices and simplified device fabrication. Here, two ambipolar anthracene derivatives containing a hole-transporting di-p-tolylamine and a carbazole and an electron-transporting phosphine oxide moiety are rationally designed and synthesized. The thermal and optoelectronic properties were investigated and the neat films of these compounds show high photoluminescence quantum yields of 84–87%. Non-doped OLEDs with these luminogens exhibit green emission at ∼545 nm and an EQEmax of over 7.2% due to the delayed fluorescence resulting from triplet–triplet annihilation (TTA). The devices show a high luminance of over 104 400 cd m−2. Power efficiency and current efficiency maxima are up to 23.0 lm W−1 and 28.3 cd A−1, respectively. Moreover, the devices show very low efficiency roll-off and retain 90% of the maximum efficiency even at 20 000 cd m−2. When combined with a thermally activated delayed fluorescent (TADF) assistant dopant, the green-emitting OLEDs show a high EQEmax of 17.8%.PostprintPeer reviewe

Pd-Catalyzed π‑Chelation Assisted <i>ortho</i>-C–H Activation and Annulation of Allylarenes with Internal Alkynes

The synthesis of highly substituted naphthalenes from allylarenes and alkynes is described. This reaction proceeds via π-coordination of an allylic carbon–carbon double bond to the Pd(II) center and is followed by <i>ortho</i> selective C–H bond activation

Allylic Carbon–Carbon Double Bond Directed Pd-Catalyzed Oxidative <i>ortho</i>-Olefination of Arenes

Pd-catalyzed selective <i>ortho</i>-olefination of arenes assisted by an allylic C–C double bond at room temperature using O₂ as a terminal oxidant is described. A possible mechanism involving the initial coordination of allylic CC bond to Pd followed by selective <i>o</i>-C–H bond metalation is proposed

Allylic Carbon–Carbon Double Bond Directed Pd-Catalyzed Oxidative <i>ortho</i>-Olefination of Arenes

Pd-catalyzed selective <i>ortho</i>-olefination of arenes assisted by an allylic C–C double bond at room temperature using O₂ as a terminal oxidant is described. A possible mechanism involving the initial coordination of allylic CC bond to Pd followed by selective <i>o</i>-C–H bond metalation is proposed

C4-H indole functionalisation : precedent and prospects

C4-decorated indoles feature in a plethora of bioactive and functional compounds of importance to natural product synthesis, material sciences, as well as crop protection and pharmaceutical industries. Traditionally, their syntheses largely involved harsh stoichiometric metalations and radical reactions. However, transition metal catalysed C-H activation has recently evolved into a powerful strategy for the late-stage diversification of indoles at the C4-H position. Modern photoredox, enzymatic and precious transition metal catalysis represent the key stimuli for developing challenging C-C and C-Het bond forming transformations under mild reaction conditions. Herein, we discuss the evolution and application of these methods for the step-economical transformations of otherwise inert C4-H bonds up to December 2017

Expedient C–H Chalcogenation of Indolines and Indoles by Positional-Selective Copper Catalysis

A versatile protocol for the C–H chalcogenation of indolines and indoles by means of copper catalysis was established. The C–H functionalization occurred selectively at the C7 position of indolines and exclusively at the C(2)–H bonds of indoles. The robust copper catalyst tolerated a wide range of functional groups and set the stage for the synthesis of diversely decorated indoles. Mechanistic studies were indicative of a SET-type mechanism and a facile C–H metalation being operative

Palladium-Catalyzed Dehydrogenative β‑Arylation of Simple Saturated Carbonyls by Aryl Halides

A versatile palladium-catalyzed synthesis of highly substituted α,β-unsaturated carbonyl compounds has been developed. In contrast to the known Heck-type coupling reaction of unsaturated carbonyl compounds with aryl halides, the present methodology allows the use of stable and readily available saturated carbonyl compounds as the alkene source. In addition, the reaction proceeds well with low catalyst loadings and does not require any expensive metal oxidants or ligands. A variety of saturated aldehydes, ketones, and esters are compatible for the reaction with aryl halides under the developed reaction conditions to afford α,β-unsaturated carbonyl compounds in good to excellent yields. A possible reaction mechanism involves a palladium-catalyzed dehydrogenation followed by Heck-type cross couplings

Rh^III-Catalyzed [4 + 1] Annulations of 2‑Hydroxy- and 2‑Aminobenzaldehydes with Allenes: A Simple Method toward 3‑Coumaranones and 3-Indolinones

A novel method for the regio- and stereoselective synthesis of substituted 3-coumaranones from salicylaldehydes and allenes using a rhodium­(III) catalyst has been developed. This procedure gives access to new 2-vinyl-substituted 3-coumaranone compounds. The method involves a Rh^III-catalyzed aldehyde C–H activation and annulation reactions. Moreover, this Rh^III-catalyzed [4 + 1] annulation reaction has been applied to 2-aminobenzaldehydes to afford 2,2-disubstituted 3-indolinones

Rh^III-Catalyzed [4 + 1] Annulations of 2‑Hydroxy- and 2‑Aminobenzaldehydes with Allenes: A Simple Method toward 3‑Coumaranones and 3-Indolinones

A novel method for the regio- and stereoselective synthesis of substituted 3-coumaranones from salicylaldehydes and allenes using a rhodium­(III) catalyst has been developed. This procedure gives access to new 2-vinyl-substituted 3-coumaranone compounds. The method involves a Rh^III-catalyzed aldehyde C–H activation and annulation reactions. Moreover, this Rh^III-catalyzed [4 + 1] annulation reaction has been applied to 2-aminobenzaldehydes to afford 2,2-disubstituted 3-indolinones