Eudistomins Y-Inspired Design and Divergent Optimization of Heteroaryl Ketones for New Antifungal Leads

The discovery of structurally distinct leads is imperative in modern agrochemical science. Inspired by eudistomins Y and the framework-related pharmaceuticals, aryl heteroaryl ketone was drawn as a common model intriguing the design and divergent synthesis of 14 kinds of heteroaryl ketones aligned with their oxime derivatives. Antifungal function-oriented phenotypical screen protruded benzothiazolyl-phenyl oxime 5a as a promising model, and the concomitant modification led to benzothiazolyl oxime 5am (EC50 = 5.17 μM) as a superior lead than fluoxastrobin (EC50 = 7.54 μM) against Sclerotinia sclerotiorum. Scaffold hopping of the phenyl subunit identified benzothiazolyl-pyridyl oxime as a novel antifungal scaffold accompanied by acquiring oxime 5bm with remarkable activity (EC50 = 3.57 μM) against Pyricularia oryzae. Molecular docking showed that candidate 5am could form more hydrogen bonds with the amino acid residues of actin than metrafenone. This compound also demonstrated better curative efficacy than that of fluoxastrobin and metrafenone in controlling the plant disease caused by S. sclerotiorum. These results rationalize the discovery of antifungal candidates based on aryl heteroaryl ketone.

Sustainable preparation of 2-acylbenzothiazoles under the cooperation of ionic liquids and microwave irradiation

Microwave irradiation (MW) and ionic liquids (ILs) are two of the most promising relatively greener synthetic approaches to preparing value-added chemicals. Herein, a series of 2-acylbenzothiazole derivatives were synthesized for the first time from commercially available α-bromoacetophenones and disulfane-diyl-dianilines through the cooperation of ionic liquids and microwave irradiation under metal- and extra-additives-free conditions. A plausible mechanism involving the successive IL-induced enolation has been proposed.

Synthesis of 2-benzyl benzoxazoles and benzothiazoles via elemental sulfur promoted cyclization of styrenes with 2-nitrophenols and N,N-dialkyl-3-nitroanilines

Herein we report a method for affording 2-benzyl benzoxazoles from substituted styrenes and 2-nitrophenols. The success of this method relies on the use of simple reagents, namely elemental sulfur and DABCO. A combination of identical reagents was utilized for the annulation of styrenes with N,N-dialkyl-3-nitroanilines to afford 2-benzyl benzothiazoles. Overall, benzoxazoles and benzothiazoles bearing useful functionalities such as halogens, amines, and heterocyclic groups were isolated in moderate to good yields. Our methods are a rare example of divergent transformations of substituted nitroarenes towards 2-benzyl benzoxazoles and benzothiazoles.

Elemental Sulfur-Promoted Benzoxazole/Benzothiazole Formation Using a C═C Double Bond as a One-Carbon Donator

An efficient method to assemble diverse benzoxazoles/benzothiazoles in good yields was developed via oxidative cyclization with 2-aminothiophenols or 2-iodoanilines as raw materials. In this protocol, elemental sulfur was used as the effective oxidant and C atoms on the C═C double bond were introduced as a one-carbon donator.

Isatin as a 2-aminobenzaldehyde surrogate: transition metal-free efficient synthesis of 2-(2'-aminophenyl)benzothiazole derivatives

A transition metal-free, convenient, and efficient practical approach has been devised for the synthesis of substituted 2-(2'-aminophenyl)benzothiazoles via a sulfur insertion strategy using isatin derivatives as 2-aminobenzaldehyde surrogates. KI assisted one-pot operation of isatin, arylamines and elemental sulfur resulted in the formation of a C-N and two C-S bonds and cascade cleavage of the isatin ring resulting in the formation of 2-(2'-aminophenyl)benzothiazoles. The significant features of this strategy are the readily available and inexpensive starting materials, broad substrate scope, sustainable reaction conditions and high yield of products. Importantly, the strategy was found to be appropriate for gram scale synthesis (>10 g) of 2-(2'-aminophenyl)benzothiazole derivatives. Moreover, the excellent photophysical properties (ΦF up to 60%) of 2-(2'-aminophenyl)benzothiazole derivatives provide huge scope in materials science.

New synthesis of 2-aroylbenzothiazoles via metal-free domino transformations of anilines, acetophenones, and elemental sulfur

A new synthesis of 2-aroylbenzothiazoles via iodine-promoted domino transformations of anilines, acetophenones, and elemental sulfur was demonstrated. The highlights of this tandem synthesis are (1) easily available anilines and acetophenones as feedstock; (2) transition metal-free conditions; (3) inexpensive, nontoxic, easy handling, and abundant elemental sulfur as a building block. This synthetic strategy would complement the existing methods in the synthesis of this important heterocyclic scaffold. To our best knowledge, the formation of 2-aroylbenzothiazoles from simple anilines, acetophenones, and elemental sulfur was not previously reported in the literature.

A new synthesis of 2-aroylbenzothiazoles via iodine-promoted domino transformations of anilines, acetophenones, and elemental sulfur was demonstrated.

Visible light initiated amino group ortho-directed copper(i)-catalysed aerobic oxidative C(sp)-S coupling reaction: synthesis of substituted 2-phenylbenzothiazoles via thia-Wolff rearrangement

A facile amino group ortho-directed visible-light-driven copper-catalysed aerobic oxidative C(sp)-S coupling reaction of a dimer of 2-aminothiophenol with terminal alkynes was achieved. This photochemical reaction shows an excellent conversion and chemoselectivity towards the formation of C(sp)-S coupling and has been employed for a wide range of thiol dimers, and alkynes. Furthermore, the synthetic utility of the synthesized alkynyl sulfides was demonstrated as a direct method for the construction of 2-phenylbenzothiazoles from the corresponding alkynyl sulfides via "thia-Wolff rearrangement" using AgNO3 and visible light using 9-mesityl-10-methylacridinium ions (Acr+-Mes) as photoredox catalyst system.

Synthesis of 2-aryl-benzothiazoles via Ni-catalyzed coupling of benzothiazoles and aryl sulfamates

2-Aryl-benzothiazoles have been successfully synthesized via a simple coupling reaction between benzothiazoles and aryl sulfamates using a nickel catalyst. The nickel catalyst is inexpensive, reusable and commercially available. In addition, the use of highly expensive palladium catalysts and unstable raw materials has been avoided. 2-Aryl-benzothiazoles bearing various substituents on the aryl groups were obtained in good yield.

I2-Promoted Multicomponent Dicyclization and Ring-Opening Sequences: Direct Synthesis of Benzo[e][1,4]diazepin-3-ones via Dual C-O Bond Cleavage

A novel and efficient formal [4 + 2+1] annulation of aryl methyl ketones and 2-aminobenzyl alcohols for the synthesis of benzo[e][1,4]diazepin-3-ones is reported. This reaction successfully affords diverse seven-membered ring lactams via dual C-O bond cleavage. A preliminary mechanistic study showed that a multicomponent dicyclization and ring-opening sequence might occur, with the introduction of methyl sulfide proposed as the last step. This efficient strategy with mild reaction conditions and a broad substrate scope has potential applications in chemistry and medicine.

Metal-free synthesis of imidazo[1,5-a]pyridines via elemental sulfur mediated sequential dual oxidative Csp3-H amination

A simple and efficient approach has been developed for the synthesis of imidazo[1,5-a]pyridines using the elemental sulfur mediated sequential dual oxidative Csp3-H amination of 2-pyridyl acetates and amines under metal- and peroxide-free conditions. Broad substrate scope, operational simplicity and gram-scale ability make this chemistry very practical.

An efficient synthesis of benzothiazole using tetrabromomethane as a halogen bond donor catalyst

A CBr₄ catalyzed simple, mild, and efficient protocol has been developed for the synthesis of 2-substituted benzothiazole from 2-aminothiophenols and N-methylthioamides under solvent free conditions.