Christophe Hoarau

Palladium-catalyzed direct (hetero)arylation of ethyl oxazole-4-carboxylate: an efficient access to (hetero)aryloxazoles.

A straightforward route toward 2-(hetero)arylated and 2,5-di(hetero)arylated oxazoles through regiocontrolled palladium-catalyzed direct (hetero)arylation of ethyl oxazole-4-carboxylate with iodo-, bromo-, and chloro(hetero)aromatics followed by a two-step hydrolysis/decarboxylation sequence was described. The method was applied here to a neat synthesis of two 2,5-di(hetero)aryloxazole natural products, balsoxin and texaline.

Carbonates: eco-friendly solvents for palladium-catalysed direct arylation of heteroaromatics

The palladium-catalysed direct 2-, 4- or 5-arylation of a wide range of heteroaromatics with aryl halides proceed in moderate to good yields using the eco-friendly solvents carbonates. The best yields were obtained using benzoxazole or thiazole derivatives. The arylation of furan, thiophene, pyrrole, imidazole or isoxazole derivatives was found to require a more elevated reaction temperature.

Direct C-2 arylation of alkyl 4-thiazolecarboxylates: new insights in synthesis of heterocyclic core of thiopeptide antibiotics.

The Pd(0)-catalyzed regioselective C-2 (hetero)arylation of tert-butyl 4-thiazolecarboxylate with a broad (hetero)aryl halide is reported, including the direct coupling of pyridinyl halides. The process has allowed the preparation of valuable 2-pyridynyl-4-thiazolecarboxylates which are components of the complex heterocyclic core of thiopeptides antibiotics. As a first application, a synthesis of a tert-butyl sulfomycinamate thio-analogue from tert-butyl 4-thiazolecarboxylate is here described through a three-step direct pyridinylation, halogenation, and Stille cross-coupling sequence.

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

Summary Catalytic direct (hetero)arylation of (hetero)arenes is an attractive alternative to traditional Kumada, Stille, Negishi and Suzuki–Miyaura cross-coupling reactions, notably as it avoids the prior preparation and isolation of (hetero)arylmetals. Developments of this methodology in the oxazole series are reviewed in this article. Methodologies, selectivity, mechanism and future aspects are presented.

A New Approach to Isoindolobenzazepines. A Simple Synthesis of Lennoxamine

Abstract A convenient and versatile short-step synthesis of isoindolobenzazepines, illustrated by a total synthesis of the alkaloid lennoxamine 1 , is described.

Highly Efficient Borylation Suzuki Coupling Process for 4-Bromo-2-ketothiazoles: Straightforward Access to Micrococcinate and Saramycetate Esters

The first palladium-catalyzed borylation of 4-bromo-2-ketothiazoles followed by a Suzuki cross-coupling reaction with haloheteroaromatics using Buchwalds Cy-JohnPhos and XPhos ligands is reported. The methodology has allowed the fast preparation of highly valuable 4-pyridinyl- and 4-thiazolyl-2-ketothiazoles as common subunits of thiopeptide antibiotics. As direct applications, novel concise syntheses of a sulfomycinamate thio-analogue as well as micrococcinate and saramycetate esters are described.

Mechanism Selection for Regiocontrol in Base‐Assisted, Palladium‐Catalysed Direct CH Coupling with Halides: First Approach for Oxazole‐ and Thiazole‐4‐Carboxylates

Both base-assisted non-concerted metallation-deprotonation (nCMD) and concerted metallation-deprotonation (CMD) have been identified as two potent operating mechanisms in palladium-catalysed direct C-H coupling of oxazole and thiazole-4-carboxylate esters with halides through base- and solvent-effect experiments. Novel C2- and C5-selective CMD direct arylation procedures in oxazole- and thiazole-4-carboxylate series were then designed by controlling the balance between electronic and steric factors. Notably, charge interactions between the palladium catalyst and substrate were identified as a parameter for controlling selectivity and reducing the impact of steric factors in the CMD reaction.

Oxidative dearomatization of resorcinol derivatives: useful conditions leading to valuable cyclohexa-2,5-dienones

The oxidative dearomatization of resorcinol derivatives with various oxidants is examined, as is the reactivity of cyclohexa-2,5-dienone that emerged. The results of these studies are presented herein.

Diastereoselective addition of metalated isoindolin-1-ones to aldehydes. Stereoselective preparation of (E)-3-arylideneisoindolin-1-ones

Lithiated isoindolinones react with aromatic aldehydes to afford 3-hydroxybenzyl derivatives with high diastereoselectivity. Dehydration of erythro and threo adducts through an E1cb mechanism gives rise indiscriminately to the (E)-arylideneisoindolinones.

Carbonates: Ecofriendly Solvents for Palladium‐Catalyzed Direct 2‐Arylation of Oxazole Derivatives

Bien-bon-ates. Carbonates offer an environmentally friendly alternative to standard polar solvents. Since a few years, carbonates have been employed successfully for some classical metal-catalyzed reactions. Here, the palladium-catalyzed direct 2-arylation of oxazole derivatives in carbonate solvents is reported.