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A base‐promoted net‐[3+2] cycloaddition of nitriles and 1‐arylpropynes for the synthesis of pyrroles is described. The developed method provides convenient access to various 2,5‐disubstituted or 2,4,5‐trisubstituted pyrroles in 40% to 96% yields (32 examples). Among methods for the synthesis of pyrroles, the protocol presented here stands out for its convenience and atom‐economy.

 

Aziridines are highly valued synthetic targets in organic and medicinal chemistry. The organocatalytic synthesis of such structures with broad substrate scope and good diastereoselectivity, however, is rare. Herein, we report a broadly applicable and diastereoselective synthetic method for the synthesis oftrans‐aziridines from imines and benzylic or alkyl halides utilizing sulfenate anions (PhSO^–) as the catalyst. Substrates bearing heterocyclic aromatic groups, alkyl, and electron‐rich and electron‐poor aryl groups were shown to be compatible with this method (33 examples), giving good yields and high diastereoselectivities (trans:cis>20 : 1). Further functionalization of aziridines containing cyclopropyl or cyclobutyl groups was achieved through ring‐opening reactions, with a cyclobutyl‐substituted norephedrine derivative obtained through a four‐step synthesis. We offer a mechanistic proposal involving reversible addition of the deprotonated benzyl sulfoxide to the imine to explain the hightrans‐diastereoselectivity.

 

A novel, selective and high‐yielding palladium‐catalyzed carbonylative arylation of a variety of weakly acidic (pK_a25–35 in DMSO) benzylic and heterobenzylic C(sp³)−H bonds with aryl bromides has been achieved. This system is applicable to a range of pro‐nucleophiles for access to sterically and electronically diverse α‐aryl or α,α‐diaryl ketones, which are ubiquitous substructures in biologically active compounds. The Josiphos SL‐J001‐1‐based palladium catalyst was identified as the most efficient and selective, enabling carbonylative arylation with aryl bromides under 1 atm CO to provide the ketone products without the formation of direct coupling byproducts. Additionally, (Josiphos)Pd(CO)₂was identified as the catalyst resting state. A kinetic study suggests that the oxidative addition of aryl bromides is the turnover‐limiting step. Key catalytic intermediates were also isolated.

 

α‐Amino nitriles are versatile structural motifs in a variety of biologically active compounds and pharmaceuticals and they serve as valuable building blocks in synthesis. The preparation of α‐ and β‐functionalized α‐amino nitriles from readily available scaffolds, however, remains challenging. Herein is reported a novel dual catalytic photoredox/copper‐catalyzed chemo‐ and regioselective radical carbocyanation of 2‐azadienes to access functionalized α‐amino nitriles by using redox‐active esters (RAEs) and trimethylsilyl cyanide. This cascade process employs a broad scope of RAEs and provides the corresponding α‐amino nitrile building blocks in 50–95 % yields (51 examples, regioselectivity >95 : 5). The products were transformed into prized α‐amino nitriles and α‐amino acids. Mechanistic studies suggest a radical cascade coupling process.

 

Rh(I)‐catalyzed C8‐selective C−H alkenylation and arylation of 1,2,3,4‐tetrahydroquinolines with alkenyl and aryl carboxylic acids under microwave assistance have been realized. Using [Rh(CO)₂(acac)] as the catalyst and Piv₂O as the acid activator, 1,2,3,4‐tetrahydroquinolines undergo C8‐selective decarbonylative C−H alkenylation with a wide range of alkenyl and aryl carboxylic acids, affording the C8‐alkenylated or arylated 1,2,3,4‐tetrahydroquinolines. This method enables the synthesis of C8‐alkenylated 1,2,3,4‐tetrahydroquinolines that would otherwise be difficult to access by means of conventional C−H alkenylation protocols. Moreover, this catalytic system also works well in C8‐selective decarbonylative C−H arylation of 1,2,3,4‐tetrahydroquinolines with aryl carboxylic acids. The catalytic activity strongly depends on the choice of the N‐directing group, with the readily installable and removable N‐(2‐pyrimidyl) group being optimal. The catalytic pathway is elucidated by mechanistic experiments. 

A novel tandem radical cyclization/intermolecular coupling between 2-azaallyl anions and indole N-aryloxy acetamides is developed, which enables the synthesis of C3a-substituted pyrroloindolines under mild conditions.