On the Illusive Nature of o-Formylazobenzenes: Exploiting the Nucleophilicity of the Azo Group for Cyclization to Indazole Derivatives

Novel N-transfer reagent for converting α-amino acid derivatives to α-diazo compounds

A novel universal N-transfer reagent for direct and effective transformation of α-amino ketones, acetamides, and esters to the corresponding α-diazo products under mild basic conditions has been developed. This one-step synthetic approach not only allows for generation of α-substituted-α-diazo carbonyl compounds from α-amino acid derivatives but also permits preparation of α-diazo dipeptides from N-terminal dipeptides (32 examples, up to 91%).

Synthesis and Prior Misidentification of 4-tert-Butyl-2,6-dinitrobenzaldehyde

Substituted 2,6-dinitrobenzaldehydes are valuable synthetic precursors and have been prepared by several methods. We report here that one reported synthetic method actually forms the 3,5-dinitro isomer, 4-tert-butyl-3,5-dinitrobenzaldehyde, instead of the claimed 2,6-isomer, 4-tert-butyl-2,6-dinitrobenzaldehyde. Improved syntheses for the large-scale preparation of both compounds and their single-crystal X-ray structures are described.

Photochemical Preparation of 1,2-Dihydro-3 H-indazol-3-ones in Aqueous Solvent at Room Temperature

o-Nitrosobenzaldehyde is a reactive intermediate useful in the synthesis of nitrogen heterocycles. Previous strategies for using o-nitrosobenzaldehyde involve its isolation via chromatography and/or formation under harsh conditions. Herein, this intermediate was photochemically generated in situ from o-nitrobenzyl alcohols in a mild, efficient manner for the construction of 1,2-dihydro-3 H-indazol-3-ones using an aqueous solvent at room temperature. This convenient reaction offers several advantages over reported methods. The commercially available photoreactor employed 3 × 18 W bulbs outputting broad emission above 365 nm.

I2-Mediated 2H-indazole synthesis via halogen-bond-assisted benzyl C-H functionalization

I₂-Mediated benzyl C-H functionalization has been developed for the synthesis of 2H-indazoles, which features high efficiency, simple conditions and no need for metals. Mechanistic experiments and DFT calculations have revealed halogen bond assistance and a radical chain process for this reaction. The azo group and the bound iodine cooperate in the hydrogen abstraction step, which circumvents the thermodynamic disfavor of direct hydrogen abstraction by a simple iodine radical.

Synthesis of indazole motifs and their medicinal importance: an overview

Indazoles is an important class of heterocyclic compounds having a wide range of biological and pharmaceutical applications. There is enormous potential in the synthesis of novel heterocyclic systems to be used as building blocks for the next generation of pharmaceuticals as anti-bacterial, anti-depressant and anti-inflammatory. Fused aromatic 1H and 2H-indazoles are well recognized for anti-hypertensive and anti-cancer properties. The present review focuses on novel routes of their synthesis and various biological activities.

Facile Cu(I)-catalyzed oxidative coupling of anilines to azo compounds and hydrazines with diaziridinone under mild conditions

A mild and highly efficient Cu(I)-catalyzed oxidative coupling of anilines is described. Various primary and secondary anilines can be efficiently coupled under mild conditions to the corresponding azo compounds and hydrazines in high yields. This method provides a direct and practical access to these compounds and is also amenable to gram scale with no special precautions to exclude air or moisture.

An oxazolo[3,2-b]indazole route to 1H-indazolones

The novel heterocycle 2,3-dihydrooxazolo[3,2-b]indazole has been synthesized and utilized to provide easy access to 1H-indazolones, particularly the previously unreported 2-(2-alkoxyethyl)-1H-indazol-3(2H)-ones. Mechanistic as well as optimization and reaction scope studies are reported.

Benzidine Rearrangement Reactions of Polyether Tethered Cyclic N,N‘-Diaryl Hydrazides

N,N'-Diaryl hydrazides tethered with a polyether group at the meta positions undergo [5,5]-sigmatropic (benzidine) rearrangement reactions to furnish 4,4'-diamino-biphenyls (benzidines) strapped with a polyether unit at the 2,2'-positions.