Cobalt‐Catalyzed Allylic Alkylation Enabled by Organophotoredox Catalysis

Co‐catalyzed allylic substitution reactions have received little attention, arguably because of the lack of any known advantage of Co catalysis over either Rh or Ir catalysis. Described here is a general and regioselective Co‐catalyzed allylic alkylation using an in situ catalyst activation by organophotoredox catalysis. This noble‐metal‐free catalytic system exhibits unprecedentedly high reactivities and regioselectivities for the allylation with an allyl sulfone, for the first time, representing the unique synthetic utility of the Co‐catalyzed method compared to the related Rh‐ and Ir‐catalyzed reactions.     

Pd‐Catalyzed Selective Carbonylation of gem‐Difluoroalkenes: A Practical Synthesis of Difluoromethylated Esters

The first catalyst for the alkoxycarbonylation of gem‐difluoroalkenes is described. This novel catalytic transformation proceeds in the presence of Pd(acac)₂/1,2‐bis((di‐tert‐butylphosphan‐yl)methyl)benzene (btbpx) ( L4 ) and allows for an efficient and straightforward access to a range of difluoromethylated esters in high yields and regioselectivities. The synthetic utility of the protocol is showcased in the practical synthesis of a Cyclandelate analogue using this methodology as the key step.     

Asymmetric Synthesis of α,α‐Disubstituted Allylic Amines through Palladium‐Catalyzed Allylic Substitution

The first asymmetric synthesis of important α,α‐disubstituted N‐alkyl allyl amine scaffolds through allylic substitution is reported. This approach is based on palladium catalysis and features ample scope with respect to both the allylic precursor and amine reagent, and high asymmetric induction with enantiomeric ratios (e.r.) up to 98.5:1.5. The use of less‐reactive anilines is also feasible, providing enantioenriched α,α‐disubstituted N‐aryl allylic amines.     

Nucleophile Coordination Enabled Regioselectivity in Palladium‐Catalyzed Asymmetric Allylic C−H Alkylation

Branched selectivity in asymmetric allylic C?H alkylation is enabled by using 2‐acylimidazoles as nucleophiles in the presence of a chiral phosphoramidite‐palladium catalyst. A wide range of terminal alkenes, including 1,4‐dienes and allylarenes, are nicely tolerated and provide chiral 2‐acylimidazoles in moderate to high yields and with high levels of regio‐, and enantio‐, and E/Z‐selectivities. Mechanistic studies using density‐functional theory calculations suggest a nucleophile‐coordination‐enabled inner‐sphere attack mode for the enantioselective carbon–carbon bond‐forming event.     

Selective Palladium‐Catalyzed Allenic C−H Bond Oxidation for the Synthesis of [3]Dendralenes

A highly selective palladium‐catalyzed allenic C−H bond oxidation was developed, and it provides a novel and straightforward synthesis of [3]dendralene derivatives. A variety of [3]dendralenes with diverse substitution patterns are accessible with good efficiency and high stereoselectivity. The reaction tolerates a broad substrate scope containing various functional groups on the allene moiety, including ketone, aldehyde, ester, and phenyl groups. Also, a wide range of olefins with both electron‐donating and electron‐withdrawing aryls, acrylate, sulfone, and phosphonate groups are tolerated.     

Ligand‐Controlled Regiodivergent and Enantioselective Copper‐Catalyzed Hydroallylation of Alkynes

A ligand‐controlled regiodivergent and enantioselective copper‐catalyzed intermolecular hydroallylation of alkynes with allylic phosphates and hydrosilanes has been achieved for the first time. The chiral bidentate sulfonate‐containing N‐heterocyclic carbene ligated CuCl complex leads to enantioenriched S_N2′‐type products, whereas the use of the IMesCuCl catalyst affords S_N2‐type products. Thus a range of chiral branched and achiral linear 1,4‐dienes could be facilely synthesized from readily available alkynes in a regiodivergent manner.     

Ligand‐Controlled Palladium(II)‐Catalyzed Regiodivergent Carbonylation of Alkynes: Syntheses of Indolo[3,2‐c]coumarins and Benzofuro[3,2‐c]quinolinones

Regiodivergent syntheses of indolo[3,2‐c]coumarins and benzofuro[3,2‐c]quinolinones through a controllable palladium(II)‐catalyzed carbonylative cyclization are established. The chemo‐ and regioselectivity are exclusively tuned by the ligand on the palladium catalyst. The rigid framework of the electron‐deficient ligand promotes the O‐attack/N‐carbonylation cyclization leading to benzofuro[3,2‐c]quinolinones, while a sterically bulky and electron‐rich ligand facilitates N‐attack/O‐carbonylation cyclization to generate indolo[3,2‐c]coumarins. Furthermore, various other nucleophiles are applicable for delivering a variety of indoloquinolinones, pyranoquinolones, and chromeno[3,4‐c]quinolinones in one step, and serves as a method for creating compound libraries for drug discovery.