Cu-Catalysed synthesis of benzo[f]indole-2,4,9(3H)-triones by the reaction of 2-amino-1,4-napthoquinones with α-bromocarboxylates.

A copper-catalysed cascade ester amidation/radical cyclization of 2-amino-1,4-naphthoquinones with α-bromocarboxylates to afford benzo[f]indole-2,4,9(3H)-triones is described, and the reaction has a broad substrate scope and the desired products are obtained in mostly moderate to good yields. Mechanism-probing experiments indicate that the otherwise challenging radical coupling reaction of α-bromocarboxylates with 2-amino-1,4-naphthoquinones is facilitated by a 5-endo radical cyclization.

Copper-Catalyzed Three-Component Difunctionalization of Aromatic Alkenes with 2-Amino-1,4-naphthoquinones and α-Bromocarboxylates.

A copper-catalyzed three-component difunctionalization of aromatic alkenes to access 1,4-naphthoquinone derivatives with diverse structures is described. Experiments show that the difunctionalization reaction is accompanied by ester exchange reaction with the solvent. In this method, α-bromocarboxylates are used as radical precursors and 2-amino-1,4-naphthoquinones as radical trapping reagents. The substrate scope is broad because various aromatic alkenes, 2-amino-1,4-naphthoquinones, and α-bromocarboxylates are employed in the reaction, and corresponding products are obtained in moderate to good yields.

Pd-catalyzed sequential intramolecular annulation/intermolecular [3+2] cycloaddition of 5-allenyloxazolidine-2,4-diones with dipoles: synthesis of spiroheterocycles.

Pd-catalyzed sequential intramolecular annulation/intermolecular [3+2] cycloaddition of 5-allenyloxazolidine-2,4-diones with dipoles was achieved. Under palladium catalysis, various 5-allenyloxazolidine-2,4-diones reacted with 1,3-dipoles such as nitrile N-oxides, azomethine imines or nitrilimines to give a series of functionalized spiroheterocycles in high yields. The scale-up reaction and further derivation of products were successful. A plausible mechanism was also proposed based on the control experiments.

Cu-Catalyzed Divergent Transformations of Allenylethylene Carbonates with Diboron Reagents.

Divergent transformations of allenylethylene carbonates with diboron reagents catalyzed by copper are disclosed. By using CuCl/IPr·HCl as the catalyst, the allenylethylene carbonates react with B2hex2 to afford 2,4-dien-1-ols as the product in the presence of Cs2CO3 as the base, iPrOH as the additive, and 1,4-dioxane as the solvent. And they react with B2pin2 to form boronic half acids in the presence of NaOtBu as the base, water as the additive, and THF as the solvent. The reactions afford corresponding products in good stereoselectivities and yields, and further derivatizations of boronic half acids and study of the mechanism are also demonstrated.

Palladium-Catalyzed [3 + 2] Cycloaddition of 4-Vinyl-4-butyrolactones with Ketenes Generated in Situ from Acyl Chlorides: A Method for the Synthesis of Dihydrofurans.

In this paper, palladium-catalyzed [3 + 2] cycloaddition of 4-vinyl-4-butyrolactones with ketenes generated from easily available acyl chlorides was achieved. With Pd2(dba)3·CHCl3/XantPhos as the catalyst, the reaction proceeded smoothly under mild reaction conditions, affording a series of 2,3-dihydrofurans in moderate to high yields. The scale-up reaction and further transformations of the products are demonstrated, and a plausible mechanism is proposed as well.

Palladium-Catalyzed Asymmetric (3 + 2) Cycloaddition of 5-Allenyloxazolidine-2,4-Diones with Barbiturate-Derived Alkenes: Synthesis of Spirobarbiturate-γ-Lactams.

The 5-allenyloxazolidine-2,4-diones had been synthesized as novel precursors of π-allyl palladium zwitterion and were applied in a palladium-catalyzed enantioselective (3 + 2) annulation by using barbiturate-derived alkenes as the reaction partner in the presence of an axially chiral phosphoramidite ligand. This reaction proceeded smoothly under mild reaction conditions, affording highly functionalized spirobarbiturate-γ-lactam derivatives in excellent yields along with high diastereo- and enantioselectivities. The scale-up reaction and further transformation of the product were also successful.

Copper-Catalyzed Three-Component Carboboronation of Allenes Using Highly Strained Cyclic Ketimines as Electrophiles.

A diastereoselective copper and NHC-ligand-catalyzed three-component difunctionalization of allenes with bis(pinacolato)diboron and 2H-azirines to afford borylated allylaziridines is described. The reaction exhibits complete diastereoselectivity and good yields, and the further chlorination of the corresponding borylated products was also performed. It is believed that the high ring-strain force of 2H-azirines facilitates the reaction. More chemical transformations of borylated allylaziridines are also reported.