Copper(II)-Catalyzed Sequential C,N-Difunctionalization of 1,4-Naphthoquinone for the Synthesis of Benzo[<i>f</i>]indole-4,9-diones under Base-Free Condition

An efficient synthesis of benzo­[<i>f</i>]­indole-4,9-diones has been achieved by copper­(II)-catalyzed naphthoquinone sequential C,N-difunctionalization reactions with β-enaminones. New C–C and C–N bonds are easily formed in the reaction course. Copper­(II) salt plays a dual role as Lewis acid and oxidative catalyst, and O₂ acts as the terminal oxidant. The advantage of this reaction is the high atom economy with broad substrate scope and excellent yields. The reaction can be scaled up to using at least grams of substrates

CuI-Catalyzed C–N Bond Formation and Cleavage for the Synthesis of Benzimidazo[1,2‑<i>a</i>]quinazoline Derivatives

A copper­(I)-catalyzed domino reaction of <i>N</i>-(2-benzimidazolyl)-2-aminobenzamide and 2-halogenated benzaldehyde has been studied. The procedure is based on a sequential CuI-catalyzed Ullmann reaction (C–N bond formation) and two bond cleavage reactions and provides an efficient strategy for the synthesis of benzimidazo­[1,2-<i>a</i>]­quinazolines catalyzed by CuI/l-proline

Cu(OAc)₂‑Catalyzed Aerobic Oxidative Dehydrogenation Coupling: Synthesis of Heptacyclic Quinolizino[3,4,5,6-<i>kla</i>]perimidines

A Cu­(OAc)₂-catalyzed domino tricyclization between naphthalene-1,8-diamine and 2-(phenylethynyl)­benzaldehyde is described, enabling aerobic oxidative dehydrogenation coupling to access heptacyclic quinolizino­[3,4,5,6-<i>kla</i>]­perimidines. In this reaction, the formation of three new rings and four new bonds was achieved in a functional-group-compatible fashion, allowing a facile method toward fused aza-heterocycles containing both quinolizine and perimidine moieties

Synthesis of Benzo[4,5]imidazo[1,2-<i>a</i>]naphthyridine and Benzo[4,5]imidazo[2,1-<i>a</i>]isoquinoline Derivatives Catalyzed by CuI/L-Proline

<p></p> <p>The benzo[4,5]imidazo[1,2-<i>a</i>]naphthyridines and benzo[4,5]imidazo[2,1-<i>a</i>]isoq-uino lines were obtained <i>via</i> a one-pot domino reaction of 2-(2-bromophenyl)-1<i>H</i>-benzo[<i>d</i>]imidazoles and cyclic 1,3-dicarbonyl compounds in good yields. This copper-catalyzed procedure provided an efficient method for the synthesis of fused pentacyclic heterocycles containing a α-arylation of carbonyl reaction.</p

Enantioselective Assembly of Spirocyclic Oxindole-dihydropyranones through NHC-Catalyzed Cascade Reaction of Isatins with <i>N</i>‑Hydroxybenzotriazole Esters of α,β-Unsaturated Carboxylic Acid

An NHC-catalyzed formal [4 + 2] reaction of isatins with <i>N</i>-hydroxybenzotriazole ester of α,β-unsaturated carboxylic acids bearing γ-H to construct spirocyclic oxindole-dihydropyranones featuring a chiral tetrasubstituted carbon stereogenic center was developed. The high enantioselectivity, the ready availability of the raw materials, the facile assembly, and the potential biological significance of the final products make this protocol an attractive alternative for the synthesis of spirocyclic heterocycles

N‑Heterocyclic Carbene/Lewis Acid Strategy for the Stereoselective Synthesis of Spirocyclic Oxindole–Dihydropyranones

Under the cooperative catalysis of NHC/Lewis acid, the mild, straightforward [4 + 2] annulation of α-bromo-α,β-unsaturated aldehydes bearing γ-H with isatin derivatives gave spirocyclic oxindole–dihydropyranones stereoselectively. This approach is particularly attractive due to the concise construction, avoidance of external oxidants, and the potential utilization value of final products in molecular biology and pharmacy

Combinatorial Synthesis of Fused Tetracyclic Heterocycles Containing [1,6]Naphthyridine Derivatives under Catalyst Free Conditions

A three-component reaction between an aromatic aldehyde, an amine, and <i>tert</i>-butyl 2,4-dioxopiperidine-1-carboxylate in EtOH at refluxing temperature gave fused tetracyclic heterocycles in high yields. The amines include 1<i>H</i>-indazol-5-amine, 1<i>H</i>-indazol-6-amine, 1<i>H</i>-indol-5-amine, and 1<i>H</i>-benzo­[<i>d</i>]­imidazol-5-amine, giving 11-aryl-3<i>H</i>-indazolo­[5,4-<i>b</i>]­[1,6] naphthyridine, 11-aryl-1<i>H</i>-indazolo­[6,7-<i>b</i>]­[1,6]­naphthyridine, 11-aryl-3<i>H</i>-indolo­[5,4-<i>b</i>]­[1,6]­naph-thyridine, and 11-aryl-3<i>H</i>-imidazo­[4′,5′:3,4]­benzo­[1,2-<i>b</i>]­[1,6]­naphthyridine derivatives, respectively

Combinatorial Synthesis of Fused Tetracyclic Heterocycles Containing [1,6]Naphthyridine Derivatives under Catalyst Free Conditions

A three-component reaction between an aromatic aldehyde, an amine, and <i>tert</i>-butyl 2,4-dioxopiperidine-1-carboxylate in EtOH at refluxing temperature gave fused tetracyclic heterocycles in high yields. The amines include 1<i>H</i>-indazol-5-amine, 1<i>H</i>-indazol-6-amine, 1<i>H</i>-indol-5-amine, and 1<i>H</i>-benzo­[<i>d</i>]­imidazol-5-amine, giving 11-aryl-3<i>H</i>-indazolo­[5,4-<i>b</i>]­[1,6] naphthyridine, 11-aryl-1<i>H</i>-indazolo­[6,7-<i>b</i>]­[1,6]­naphthyridine, 11-aryl-3<i>H</i>-indolo­[5,4-<i>b</i>]­[1,6]­naph-thyridine, and 11-aryl-3<i>H</i>-imidazo­[4′,5′:3,4]­benzo­[1,2-<i>b</i>]­[1,6]­naphthyridine derivatives, respectively

Synthesis of Substituted 4<i>H</i>‑Thiochromen-4-imines via Copper-Catalyzed Cyclization Cascades of <i>o</i>‑Bromobenzothioamides with Terminal Alkynes

A series of (<i>E</i>)-<i>N</i>-aryl-4<i>H</i>-thiochromen-4-imines has been conveniently obtained through a cascade reaction between <i>o</i>-bromobenzothioamides and terminal alkynes. This novel approach probably involved an initial generation of benzothietane-2-imine intermidates via an intramolecular Ullmann reaction under CuI/L-proline cocatalysis and alkaline conditions followed by imine alkynylation, ring opening, and cyclization sequences to provide the unexpected 4<i>H</i>-thiochromen-4-imines rather than isothiochromans

Copper(I)-Catalyzed Synthesis of 5‑Arylindazolo[3,2‑<i>b</i>]quinazolin-7(5<i>H</i>)‑one via Ullmann-Type Reaction

The treatment of 2-amino-<i>N</i>′-arylbenzohydrazide and <i>o</i>-halogenated benzaldehyde in the presence of CuBr and Cs₂CO₃ gave 5-arylindazolo­[3,2-<i>b</i>]­quinazolin-7­(5<i>H</i>)-one in high yields. This procedure contains an Ullmann-type reaction and provides an efficient method to construct fused tetracyclic heterocycles