Cyclohexadienone ketals and quinols: four building blocks potentially useful for enantioselective synthesis.

Publisher Summary This chapter discusses properties, structures, and reactivity of manganese redox enzymes and model systems. Manganese is one of several first-row transition elements that are employed by biological systems to assist in varied metabolic and structural roles. Manganese is used to give structural support to proteins and is a cofactor in chemical transformations that include hydrolytic and redox reactions. Perhaps the best-known function, and the one of great importance to aerobic life, is in the oxygen-evolving complex, which oxidizes water to dioxygen during photosynthesis. The discussions of data gathering on enzyme systems and model chemistry, both structural and functional, presented in this chapter provides a foundation for exploring current and as yet undiscovered manganese enzymes. The biological applications of manganese are numerous and quite varied. The manganese-containing redox enzymes are unique. Most of these deal with dioxygen metabolism in one form or another.

Manganese Redox Enzymes and Model Systems: Properties, Structures, and Reactivity

The Bronsted-acidic ionic liquid 1-methyl-3-(4-sulfobutyl)imidazolium triflate [BMIM(SO3H)][OTf] was demonstrated to act efficiently as solvent and catalyst for the halogenation of activated organic compounds with N-halosuccinimides (NXS) under mild conditions with short reaction times. Methyl aryl ketones were converted into α-halo and α,α-dihaloketones, depending on the quantity of NXS used. Ketones with activated aromatic rings were selectively halogenated, however in some cases mixtures of α-halogenated ketone and ring-halogenated ketones were obtained. Activated aromatics were regioselectively ring halogenated to give mono- and dihalo-substituted products. The [BMIM(SO3H)][OTf] ionic liquid (IL-A) was successfully reused eight times in a representative monohalogenation reaction with no noticeable decrease in efficiency. An effective halogenation scale-up in this IL is also presented. The reactivity trend and the observed chemo- and regioselectiivities point to an ET process in these IL-promoted halofunctionalization reactions.

https://www.mdpi.com/1420-3049/18/1/74/pdf

The polyamidoamine-mediated inhibition of bcl-2 by small hairpin RNA to induce apoptosis in human lens epithelial cells

1-Aryl-2,2-dichloro-7, 1-aryl-2,2-dibromo-8, 1-aryl-2-bromo-2-fluoro-9 and 1-aryl-2-chloro-2-fluoro-ethanone oximes 10 have been prepared by allowing the corresponding ketones to react with hydroxylamine hydrochloride in EtOH at room temperature. Stereochemical assignments for the oximes were made on the basis of 1H NMR spectroscopic evidence and an X-ray crystallographic analysis of 1-(3-chlorophenyl)-2,2-dichloroethanone oxime 7f. The 1-aryl-2,2-dihalogenoethanone oximes react with tetrasulfur tetranitride in refluxing 1,4-dioxane to give 3-aryl-4-chloro-1, 3-aryl-4-bromo-2, and 3-aryl-4-fluoro-1,2,5-thiadiazoles 3 in 69–98, 49–99, and 32–65% yields, respectively. A mechanism for the formation of the 1,2,5-thiadiazoles is proposed.

Reactions of 1-aryl-2,2-dihalogenoethanone oximes with tetrasulfur tetranitride (S4N4): a general method for the synthesis of 3-aryl-4-halogeno-1,2,5-thiadiazoles

The reaction of olefins with malonamide in the presence of manganese(III) acetate gave 2-buten-4-olides and/or 1H-pyrrol-2(5H)-ones in one-step, short reaction time, and moderate yields. The product distribution can be accounted for in terms of the stabilization of the intermediate carbocation in the oxidation process. The synthetic application and limitation, and the oxidation mechanism for the formations of α,β-unsaturated γ-lactones and γ-lactams are discussed.

Reaction of olefins with malonamide in the presence of manganese(III) acetate. Formation of α,β-unsaturated γ-lactones and γ-lactams

The reaction of 4′-methoxyacetophenone with manganese(III) acetate in the presence of ammonium chloride yielded 2-chloro-4′-methoxyacetophenone (2a) and 2,2-dichloro-4′-methoxyacetophenone (3a). The reaction of 2a with these reagents gave 3a, 4′-methoxy-2,2,2-trichloroacetophenone, and 1,4-bis(4-methoxyphenyl)-2,2,3,3-tetrachloro-1,4-butanedione (8a). The reactions of 2a and 2-bromoacetophenone with manganese (III) acetate yielded the corresponding 2,3-dihalo-1,4-diphenyl-1,4-butanediones, 1,4-diphenyl-2-halo-2-butene-1,4-diones, 2,3-dihalo-2-butene-1,4-diones, 2,2-dibromoacetophenone, and 8a. The reaction pathways are discussed.

The Reaction of Acetophenones with Manganese(III) Acetate

The reactions of 7-methoxy-2-phenyl-2H-1-benzopyran and 7-methoxy-2-phenyl-4H-1-benzopyran with lead(IV) acetate gave 2-benzoyl-6-methoxybenzofuran and 6-acetoxy-3-methoxy-6-(3-oxo-3-phenyl-1 -propenyl)-2,4-cyclo-hexadien-1-one. The reactions of 7-methoxy-2-(p-methoxy-phenyl)-2H-1-benzopyran and 7-methoxy-2-(p-methoxyphen-yl)-4H-1-benzopyran with lead(IV) acetate also gave the corresponding benzofuran and cyclohexadienone. The reaction pathway is discussed.

Katsutoshi Yamaguchi

Papers

The Reaction of Acetophenones with Manganese(III) Acetate

The Reactions of 2-Phenyl-2H-1-benzopyrans and 2-Phenyl-4H-1-benzopyrans with Lead(IV) Acetate

The reactions of 2-phenyl-2h-1-benzopyrans and 2-phenyl-4h-1-benzopyrans with lead(iv) acetate

The reaction of acetophenones with manganese(iii) acetate