Aldo-X Bifunctional Building Blocks for the Synthesis of Heterocycles

Aryl glyoxal: a prime synthetic equivalent for multicomponent reactions in the designing of oxygen heterocycles

The category of bifunctional building blocks overrides many others because of their fascinating wide applicability in synthetic chemistry. Aryl glyoxal is one of the key molecules that has been extensively used in heterocyclic chemistry to afford nearly all types of five- and six-membered heterocycles, which are the structural constituents of many natural products. The multicomponent reaction is a practical strategy to utilize this wonderful moiety with different types of starting materials to obtain numerous diverse oxygen heterocycles. This review covers the advancement of aryl glyoxal as a prime synthetic equivalent in recent years for the synthesis of oxygen heterocycles.

An ultrasound-assisted solvent and catalyst-free synthesis of structurally diverse pyrazole centered 1,5-disubstituted tetrazoles via one-pot four-component reaction

Abstract:

1,5-Disubstituted tetrazoles are vital drug-like scaffold usually encountered as valuable bioisosteres of cis-amide bond. In this article, we reported synthesis of some novel medicinally relevant pyrazole centered 1,5-disubstituted tetrazoles using ultrasound irradiation via a one-pot 4-C reaction from various pyrazole originated aldehyde, amine, isocyanide, and sodium azide. All the synthesized derivatives were characterized by IR, 1H NMR, 13C NMR, spectroscopic techniques, and mass analysis. This ultrasound-assisted green protocol has several advantages like mild reaction condition, high yield, catalyst and solvent-free reaction protocol, 15 minutes reaction time and easy workup.

Acid-catalyzed cleavage of C-C bonds enables atropaldehyde acetals as masked C2 electrophiles for organic synthesis

Acid-catalyzed tandem reactions of atropaldehyde acetals were established for the synthesis of three important molecules, 2,2-disubstituted indolin-3-ones, naphthofurans and stilbenes. The synthesis was realized using novel reaction cascades, which involved the same two initial steps: (i) S_N2' substitution, in which the atropaldehyde acted as an electrophile; and (ii) oxidative cleavage of the carbon-carbon bond of the generated phenylacetaldehyde-type products. Compared with literature methods, the present protocol not only avoided the use of expensive noble metal catalysts, but also enabled a simple operation.

Synthesis of C3-alkylated benzofurans via palladium-catalyzed regiocontrolled hydro-furanization of unactivated alkenes

A new chelation-controlled hydrofuranization of unactivated olefins with α-alkynyl arylols is reported for the first time, and used to produce a wide range of C₃-alkylated benzofurans with generally good yields under mild conditions.

Sulfenylation of Arenes with Ethyl Arylsulfinates in Water

A tetrabutylammonium iodide-mediated direct sulfenylation of arenes with ethyl arylsulfinates in water was developed. Various electron-rich arenes and ethyl arylsulfinates were investigated in the reaction, and a series of aryl sulfides were obtained in excellent yields. The advantages of this green protocol were simple reaction conditions (metal-free, water as the solvent, and under air), odorless and easily available sulfur reagent, broad substrate scope, and gram-scale synthesis. Moreover, the potential application of aryl sulfides was exemplified by further transformations.

One-Pot Multicomponent Synthesis and Cytotoxic Evaluation of Novel 7-Substituted-5-(1H-Indol-3-yl)Tetrazolo[1,5-a] Pyrimidine-6-Carbonitrile

A series of novel 7-substituted-5-(1H-indol-3-yl)tetrazolo[1,5-a]pyrimidine-6-carbonitrile was synthesized via a one-pot, three-multicomponent reaction of appropriate aldehydes, 1H-tetrazole-5-amine and 3-cyanoacetyl indole in catalytic triethylamine. The cytotoxic activity of the new synthesized tetrazolopyrimidine-6-carbonitrile compounds was investigated against HCT-116, MCF-7, MDA-MB-231, A549 human cancer cell lines and one human healthy normal cell line (RPE-1) using the MTT cytotoxicity assay. Compounds 4h, 4b, 4c, 4i and 4a showed potent anticancer activities against human colon cancer. Additionally, all the compounds showed potent anticancer activities on human lung cancer.

Metal-Free Air Oxidation in a Convenient Cascade Approach for the Access to Isoquinoline-1,3,4(2H)-triones

Herein we describe a very useful application of the readily available trifunctional aromatic ketone methyl-2-(2-bromoacetyl)benzoate in reactions with primary amines. An unexpected in situ air oxidation that follows a cascade process allowed the access to a series of isoquinoline-1,3,4(2H)-triones, a class of heterocyclic compounds of great interest containing an oxygen-rich heterocyclic scaffold. A modification of the original protocol, utilizing a Staudinger reaction in the presence of trimethylphosphine, was necessary for the synthesis of Caspase inhibitor trione with free NH group.