Synthesis of Diarylselenides through Rh-Catalyzed Direct Diarylation of Elemental Selenium with Benzamides.

Diarylselenides are a representative class of molecules in organoselenium compounds. We herein report a Rh-catalyzed direct diarylation of selenium with benzamide derivatives. The use of elemental selenium as the Se source is intriguing in terms of atom economy, cost, stability, and handling. A series of diarylselenides with amide moieties were readily accessible through directed C-H activation. The intermediacy of electrophilic Se(IV) species was indicated by control experiments.

Synthesis of Benzoisoselenazolones via Rh(III)-Catalyzed Direct Annulative Selenation by Using Elemental Selenium.

Isoselenazolone derivatives have attracted significant research interest because of their potent therapeutic activities and indispensable applications in organic synthesis. Efficient construction of functionalized isoselenazolone scaffolds is still challenging, and thus new synthetic approaches with improved operational simplicity have been of particular interest. In this manuscript, we introduce a rhodium-catalyzed direct selenium annulation by using stable and tractable elemental selenium. A series of benzamides as well as acrylamides were successfully coupled with selenium under mild reaction conditions, and the obtained isoselenazolones could be pivotal synthetic precursors for several organoselenium compounds. Based on the designed control experiments and X-ray absorption spectroscopy measurements, we propose an unprecedented selenation mechanism involving a highly electrophilic Se(IV) species as the reactive selenium donor. The reaction mechanism was further verified by a computational study.

Highly Diastereoselective Synthesis of Polycyclic Indolines through Formal [4+2] Propargylic Cycloaddition of Indoles with Ethynyl Benzoxazinanones.

A formal [4+2] propargylic annulation of indoles and pyrrole with ethynyl benzoxazinanones was described. This protocol provides a concise synthesis of tetrahydro-5H-indolo[2,3-b]quinolines and tetrahydro-3H-pyrrolo[3,2-b]quinoline, the core structures of alkaloid frameworks, featuring excellent yields, high diastereoselectivity, mild conditions and wide substrate scope.

Enantioselective Synthesis of 4-Allyl Tetrahydroquinolines via Copper(I) Hydride-Catalyzed Hydroallylation of 1,2-Dihydroquinolines.

CuCl/(R,R)-Ph-BPE-catalyzed asymmetric hydroallylation of 1,2-dihydroquinolines, prepared from readily available quinolines, was developed. The optically active tetrahydroquinolines (THQs) bearing an allylic functionality at position 4 were obtained in good yields and excellent enantioselectivity. The introduced allylic groups are amenable to diverse transformations, thus offering chances to rapidly expand the THQ libraries.

Chiral phosphoric acid-catalyzed asymmetric dearomatization reactions.

We summarize in this review the recent development of chiral phosphoric acid (CPA)-catalyzed asymmetric dearomatization reactions. A wide array of electron-rich arenes (indoles, phenols, naphthols, benzothiophenes, benzofurans, etc.) and electron-poor arenes (pyridines, quinolines, isoquinolines, etc.) has been proved reactive towards various reaction partners in the presence of a CPA catalyst, enabling asymmetric dearomatization reactions that lead to structurally-diverse polycyclic molecules. The reactions are grouped according to the roles of the arenes in the reactions (as nucleophiles or electrophiles) and the types of reaction partners. This review closes with a personal perspective on the dynamic research area of asymmetric dearomatization reactions by CPAs.

Enantioselective Synthesis of 4-Aminotetrahydroquinolines via 1,2-Reductive Dearomatization of Quinolines and Copper(I) Hydride-Catalyzed Asymmetric Hydroamination.

A 1,2-reductive dearomatization of quinolines and copper(II) acetate monohydrate/( R, R)-Ph-BPE/P( p-tolyl)3-catalyzed enantioselective hydroamination sequence was developed, affording diverse 4-amino-1,2,3,4-tetrahydroquinolines with high levels of enantioselectivity in either a stepwise or one-pot fashion. Pleasingly, internal cis-cyclic alkenes, which are challenging substrates in copper hydride-catalyzed enantioselective hydroamination reactions, were transformed efficiently under mild conditions.

Copper-Catalyzed Ring Opening of Benzofurans and an Enantioselective Hydroamination Cascade.

A copper(II) acetate/(R)-DTBM-SEGPHOS-catalyzed ring opening of benzofurans and enantioselective hydroamination cascade with dimethoxymethylsilane (DMMS) and hydroxylamine esters is described. Starting from readily available substituted benzofurans, a series of chiral N,N-dibenzylaminophenols, which are of high interest in pharmaceutical chemistry, were obtained with excellent enantioselectivities (up to 66 % yield, 94 % ee).