Optimization of Manganese Coupling Reaction for Kilogram-Scale Preparation of Two Aryl-1,3-dione Building Blocks

Abstract

Aryl-1,3-diones represent a promising new class of herbicidal acetyl-CoA carboxylase (ACCase) inhibitors. The original synthesis of this structural motif employed in the research phase involved a selenium oxide mediated oxidation, the use of diazoacetate and aryl lead reagents, and a low temperature oxidation of an aryl lithium intermediate, so it was not well suited to large scale synthesis. For kilogram scale synthesis of the two aryl-1,3-dione building blocks (3 and 4), we developed an alternative route which employs a manganese or manganese−copper catalyzed alkyl Grignard coupling and a semi-pinacol rearrangement of an epoxide as the key steps. The optimized conditions could be of general interest as scalable methods for the synthesis of 2-alkyl substituted benzaldehydes and of 2-aryl-1,3-diones.

Atom Economical Photocatalytic Oxidation of Phenols and Site-Selective Epoxidation Toward Epoxyquinols

“…Aldehyde 5 was obtained in three steps following the procedure described by the group of Smejkal . Aldehyde 5 (500 mg, 3.68 mmol) and silica (700 mg) were placed in dichloromethane (5 mL).…”

Eco-friendly methoximation of aromatic aldehydes and ketones using MnCl 2 .4H 2 O as an easily accessible and efficient catalyst

“…This mild and moisture compatible Lewis acid has been found to promote a handful of relevant transformations, such as mesylate to chloride conversion [44], esterification and transesterification reactions [45,46], Michael addition [47], glucose to fructose isomerization [48], condensation of carbonyls with amine derivatives [49], carbonyl reduction [50] and the reductive amination of ketones [51]. The salt has also been employed as a catalyst for cross couplings leading to C-X (X=N, S) [52,53] or C-C bond formation [54,55], and in C-H activation reactions resulting in further C-C bond formation [56][57][58][59]. MnCl 2 .4H 2 O was also supported on montmorillonite K-10, and used in the catalytic synthesis of benzaldehyde derivatives, by the H 2 O 2 -mediated oxidation of the corresponding alcohols [60].…”

Enolate SNAr of unactivated arenes via [(η6-arene)RuCp]+ intermediates

“…Enolate-based S N Ar: initial conditions and optimisation: initially, to achieve the desired S N Ar reaction, complex 1a was reacted in the presence of 1,3-cyclohexanedione and potassium carbonate in DMF at 40 1C (Table 1, entry 1). Following purification, analysis by multinuclear NMR spectroscopy confirmed an arene transformation, as evidenced by shifts in the aromatic signals and appearance of new signals corresponding to the reacted dione nucleophile, as well as a disappearance of the aromatic fluorine signal in the 19 F NMR spectrum. The mass spectrum also showed a molecular ion with the predicted mass of the product complex, confirming substitution had taken place.…”