Photoinduced Nickel-Catalyzed Chemo- and Regioselective Hydroalkylation of Internal Alkynes with Ether and Amide α-Hetero C(sp³)–H Bonds

Abstract

A direct hydroalkylation of disubstituted alkynes with unfunctionalized ethers and amides was achieved in an atom-efficient and additive-free manner through the synergistic combination of photoredox and nickel catalysis. The protocol was effective with a wide range of internal alkynes, providing products in a highly selective fashion. Notably, the observed regioselectivity is complementary to conventional radical addition processes. Mechanistic investigations suggest that the photoexcited iridium catalyst facilitated the nickel activation via single-electron transfer.

Microtubing‐Reactor‐Assisted Aliphatic C−H Functionalization with HCl as a Hydrogen‐Atom‐Transfer Catalyst Precursor in Conjunction with an Organic Photoredox Catalyst

“…SCE) and suitability for oxidizing Cl anion to Cl radical (E ox (Cl À /Cl · ) =+2.03 Vv s. SCE). [13] As part of our ongoing interest in developing visible-light-promoted transformations using readily available C(sp 3 ) À Hb onds as the latent nucleophilic handles, [7,14] we herein report am etal-free C À Ha lkylation and allylation assisted by microtubing reactors with HCl as aH AT catalyst precursor in conjunction with Mes-Acr + as aphotoredox catalyst (Scheme 2c). [9] Continuous microflow technologies have provided effective platforms for photochemical synthesis owing to the improved light penetration associated with microtubing reactors.…”

“…The key to success relied on the utilization of microtubing reactors to maintain the volatile HCl catalyst. In this regard, Doyle and co-workers and our group recently demonstrated the generation of chlorine radical by photolysis of aNi III chloride intermediate generated by photoredox-mediated single-electron oxidation of aNi II precursor and showed that it could activate C(sp 3 )ÀH bonds for arylation [6] and hydroalkylation of alkynes, [7] respectively (Scheme 2a). [1] In particular,t he synergistic combination of photoredox catalysts and hydrogen-atom-transfer (HAT) catalysts has offered enormous opportunities for C(sp 3 ) À Ha ctivation.…”

“…In this regard, Doyle and co-workers and our group recently demonstrated the generation of chlorine radical by photolysis of aNi III chloride intermediate generated by photoredox-mediated single-electron oxidation of aNi II precursor and showed that it could activate C(sp 3 )ÀH bonds for arylation [6] and hydroalkylation of alkynes, [7] respectively (Scheme 2a). In this regard, Doyle and co-workers and our group recently demonstrated the generation of chlorine radical by photolysis of aNi III chloride intermediate generated by photoredox-mediated single-electron oxidation of aNi II precursor and showed that it could activate C(sp 3 )ÀH bonds for arylation [6] and hydroalkylation of alkynes, [7] respectively (Scheme 2a).…”

Palladium‐katalysierte intermolekulare Aryliodierung von internen Alkinen

“…B. Aryl-Ni II -Komplexen oder Arylboronsäuren verknüpfen. [3,10,18] Theoretisch wäre eine einfache Additionsreaktion zwischen leicht erhältlichen Arylhalogeniden und Alkinen die vielseitigste Route zu Alkenylhalogeniden (Schema 1d). Alternative radikalische Strategien leiden unter schneller (E)/(Z)-Isomerisierung aufgrund der Instabilitätd es Alkenyl-Intermediates.…”

Chemoselective Synthesis of Z‐Olefins through Rh‐Catalyzed Formate‐Mediated 1,6‐Reduction

“…Cis-selective carbonyl olefination reactions using phosphorus-, silicon-or sulfur-containing precursors have enabled the preparation of Z-olefins in amyriad of settings. [5,6] Despite their remarkable and growing utility,alkyne semi-reduction and Z-selective metathesis reactions can exhibit poor chemoselectivity on targets bearing multiple alkyne or olefin units.T here remains aneed for complementary catalytic approaches to Z-olefins in the presence of other carbon-carbon p-bonds and protic or electrophilic groups. Furthermore,t he strongly basic reaction conditions are often incompatible with protic or electrophilic functionality.…”