Ruthenium Catalyzed C–H Selenylations of Aryl Acetic Amides and Esters via Weak Coordination

Abstract

An efficient ruthenium-catalyzed direct C−H selenylation of aryl acetic amides and esters has been achieved via distal weakly coordination. Notable features of this protocol including broad substrate scope, wide functional group tolerance, and good regioselectivity. In addition, diaryl disulfides were also successfully applied to this reaction under slightly modified conditions.

Palladium‐Catalyzed Distal C−H Selenylation of 2‐Aryl Acetamides with Diselenides and Selenyl Chlorides

“…More recently, our group reported a ruthenium(II)catalyzed distal chalcogenation of aromatic C(sp 2 )À H bonds with diselenides and disulfides through weak coordination. [13] However, these reactions require excess diselenide or disulfide reagents and additional additives for complete conversion. Furthermore, only para-and meta-substituted 2-aryl acetamides and electron-deficient diselenides were compatible with this catalytic reaction.…”

“…Note that attempts to activate heteroaryl, naphthyl, and ortho-substituted aryl CÀ H bonds by the previous report on ruthenium (III) catalyst assisted by simple amide directing groups have, unfortunately, met with limited success and only resulted in unsatisfactory yields. [13] Subsequently, a wide range of substituted diaryl diselenides was evaluated under the optimized reaction conditions. As depicted in Scheme 4, diaryl diselenides bearing either electron-withdrawing (2 b-2 e, 2 h-2 j) or electron-donating groups (2 f-2 g) on para-, metaor ortho-position showed high reactivity under the optimized conditions to give the selected monoselenylated products in medium to high yields.…”

A Chemistry for Incorporation of Selenium into DNA‐Encoded Libraries

“…After that, Zhang (Ru II ), Baidya (Cu II ) and Ackermann (Ni II ) further developed several new catalytic systems. Very recently, Zhang and Ma developed ortho ‐C−H selenylation of weakly coordinated directing groups (benzaldehydes vs. aryl acetic amides and esters) via Pd II or Ru II ‐catalysis, respectively (Scheme a). Despite this progress these works have all been limited to simple selenylation, and use selenyl chloride or diselenide as the selenide reagent, which would no doubt result in low atom economy.…”

“…[23a,b] However,most work has been limited to traditional cross-coupling reactions using pre-functionalized substrates such as aryl halides.I nt his context, constructing aryl selenide scaffolds via direct selenylation of inert aryl C À Hb onds would be am ore straightforward and intriguing strategy. [24] In 2014, Nishihara [25a] and Li [26] independently pioneered CÀHselenylation of arenes via Pd II or Rh III -catalysis,r espectively.A fter that, Zhang (Ru II ), [27] Baidya (Cu II ) [28] and Ackermann (Ni II ) [29] further developed several new catalytic systems.V ery recently, Zhang [30] and Ma [31] developed ortho-C À Hs elenylation of weakly coordinated directing groups (benzaldehydes vs.a ryl acetic amides and esters) via Pd II or Ru II -catalysis,r espectively (Scheme 1a). Despite this progress these works have all been limited to simple selenylation, and use selenyl chloride or diselenide as the selenide reagent, which would no doubt result in low atom economy.I na ddition, selenium-based transformations also suffer from one or more other drawbacks,i ncluding (1) longer reaction times,( 2) harsh conditions (strong acid or base), and (3) the need for excessive additives (acid, base,o xidant).…”

“…Despite this progress these works have all been limited to simple selenylation, and use selenyl chloride or diselenide as the selenide reagent, which would no doubt result in low atom economy.I na ddition, selenium-based transformations also suffer from one or more other drawbacks,i ncluding (1) longer reaction times,( 2) harsh conditions (strong acid or base), and (3) the need for excessive additives (acid, base,o xidant). [25][26][27][28][29][30][31][32] Therefore,anew,s imple and practical method of CÀHs elenylation accompanied by the introduction of multiple functional groups (FGs) remains highly desirable.…”