Cu2O-Catalyzed Tandem Ring-Opening/Coupling Cyclization Process for the Synthesis of 2,3-Dihydro-1,4-benzodioxins

Total Synthesis of (-)-Amovillosumin A and Structure Correction of (-)-Amovillosumin C Using Chemical Synthesis

Norlignans are a rare class of natural products isolated from a diverse range of plant species, many of which have interesting biological activities including antibacterial, antioxidant, phytotoxic, platelet aggregation inhibitory effects, and more. Isolated from Amomum villosum (Amomi Fructus), amovillosumins A (1) and C (3) are norlignans which were of interest to synthesize, due to their interesting bioactivities, specifically their ability to increase stimulation of glucagon-like peptide-1 (GLP-1) secretion. In this research, key intermediate 15 was used to stereoselectively synthesize (7R,8R)-amovillosumins A (1) and C (3). The developed method includes a Mitsunobu coupling, a modified rhodium-catalyzed Miyaura arylation, and an acid-catalyzed cyclization in key bond-forming steps. After synthesis, the structure of 1 was confirmed, but it was revealed that the benzodioxane-containing structure of amovillosumin C (3) that had been proposed in the literature was incorrect. Thus, with further investigation a structure correction of 3 was achieved by synthesis, the correct structure being 8-O-4'-oxynorlignan.

Cu-Catalysed tandem reactions for building poly hetero atom heterocycles-green chemistry tool

Of late, regio-selective tandem reactions are given much attention due to the formation of several multiple bonds in a single synthetic operation, avoids altering the reaction conditions, isolation of the intermediates during the reaction, reduces the production of toxic waste to the environment and can produce highly complex organic molecules with desired selectivity. Though, it requires the well-built knowledge for optimization of the process, it permits to make the complex organic molecules with least number of steps, and it has eventually made great interest and inspiration to the upcoming organic chemists. Presentation of current book chapter presents the Cu-Catalysed tandem reactions for building poly hetero atom heterocyclic compounds via green approach.

A facile construction of oxygen heterocycles by the reaction of benzoxepine-4-carboxylates with dihaloalkanes and activated alkynes

This manuscript describes the preparation of heterocyclic compounds such as naphtho[1,3]-dioxoles (3a-h), [1,4]-dioxines (4a-h), [1,4]-dioxepines (5a-c), [1,4]-dioxocines (6a-c) and diethyl 2-(2-ethoxy-2-oxoethyl)naphtho[1,3]dioxoles (8a-f). These heterocyclic compounds have been achieved by the reaction of benzoxepine-4-carboxylates (1a-h) with dihaloalkanes (2a-e) and activated alkyne (7a) for the first time. This work represents the first example for the construction of utile oxygen heterocycles by the formation of C-C and C-O bonds in a one step process.

Dialkyl Carbonates in the Green Synthesis of Heterocycles

This review focuses on the use of dialkyl carbonates (DACs) as green reagents and solvents for the synthesis of several 5- and 6-membered heterocycles including: tetrahydrofuran and furan systems, pyrrolidines, indolines, isoindolines, 1,4-dioxanes, piperidines, and cyclic carbamates. Depending on the heterocycle investigated, the synthetic approach used was different. Tetrahydrofuran systems, pyrrolidines, indolines, isoindoline, and 1,4-dioxanes were synthesized using dimethyl carbonate (DMC) as sacrificial molecule (BAc2/BAl2 mechanism). Cyclic carbamates, namely 1,3-oxazin-2-ones, were prepared employing DACs as carbonylating agents, either by BAc2/BAl2 mechanism or through a double BAc2 mechanism. Piperidines were synthetized taking advantage of the anchimeric effect of a new family of dialkyl carbonates, i.e., mustard carbonates. Finally, in the case 5-hydroxymethylfurfural (HMF), DMC has been employed as efficient extracting solvent of this extensively investigated bio-based platform chemical from the reaction mixture. These synthetic approaches demonstrate, once again, the great versatility of DACs and their-yet to be fully explored-potential as green reagents and solvents in the synthesis of heterocycles.

Dual photoredox and nickel-catalyzed desymmetric C–O coupling reactions: visible light-mediated enantioselective synthesis of 1,4-benzodioxanes

Chiral 2,2′-bipyridine ligands are key to success in an enantioselective desymmetric C–O cross coupling reaction via dual visible light photoredox and nickel catalysis, resulting in chiral 1,4-benzodioxanes under mild reaction conditions.

Synthesis and biology of 1,4-benzodioxane lignan natural products

This review describes the evolution of synthetic methods towards 1,4-benzodioxane lignan natural products, from early biomimetic approaches to recent enantiospecific syntheses. Additionally, a comprehensive report of their biosynthesis and significant biological activities is detailed.

Synthesis of 3-substituted and 2,3-disubstituted quinazolinones via Cu-catalyzed aryl amidation

CuI/4-hydroxy-L-proline catalyzed coupling of N-substituted o-bromobenzamides with formamide takes place at 80 °C, affording 3-substituted quinazolinones directly. Under these conditions other amides that were tested only provided simple coupling products, which can be converted into 2,3-disubstituted quinazolinones via HMDS/ZnCl(2) mediated condensative cyclization.

The N-aryl aminocarbonyl ortho-substituent effect in Cu-catalyzed aryl amination and its application in the synthesis of 5-substituted 11-oxo-dibenzodiazepines

Double amination of ortho-substituted aryl bromides proceeded under mild conditions to afford 5-substituted 11-oxo-dibenzodiazepines, which revealed that there is a strong ortho-substituent effect caused by N-aryl aminocarbonyl groups during copper-catalyzed aryl amination.

Alumina-supported Cu(II), a versatile and recyclable catalyst for regioselective ring opening of aziridines and epoxides and subsequent cyclization to functionalized 1,4-benzoxazines and 1,4-benzodioxanes

An easily accessible catalyst, alumina-supported copper(II), efficiently catalyzes the ring opening of aziridines and epoxides followed by cyclization of the corresponding intermediate to produce a variety of functionalized 1,4-benzoxazines and 1,4-benzodioxanes, respectively, in one pot without any ligand in high yields. The ring cleavages of aziridines and epoxides are highly regioselective. The catalyst is inexpensive, non-air-sensitive, environmentally friendly, and recyclable. The function of the catalyst and the reaction pathway are postulated. This protocol is successfully utilized for the formation of three carbon-heteroatom bonds, namely, C-O, C-N, and C-S, in one pot.

Copper-catalyzed tandem process: an efficient approach to 2-substituted-1,4-benzodioxanes

An efficient method for the preparation of various 2-substituted-1,4-benzodioxanes by CuBr-catalyzed tandem reactions of 2-((o-iodophenoxy)methyl)oxiranes with phenols has been developed. The reaction involves the ring-opening process of 2-((2-iodophenoxy)methyl)oxirane followed by an intramolecular C-O cross coupling cyclization.