An Efficient Procedure for the Synthesis of α,β-Unsaturated Ketones and Its Application to Heterocyclic Systems

Synthesis of 2,2,6-Trisubstituted 5-Methylidene-tetrahydropyran-4-ones with Anticancer Activity

In our continuous search for new, relatively simple 2-alkylidene-1-oxoheterocycles as promising anticancer drug candidates, herein we report an efficient synthesis of 2,2,6-trisubstituted 5-methylidenetetrahydropyran-4-ones. These compounds were obtained in a four step reaction sequence, in which starting diethyl 2-oxopropylphosphonate was transformed into 2,2-disubstituted 5-diethoxyphosphoryldihydropyran-4-ones, followed by Michael addition of various Grignard reagents and Horner-Wadsworth-Emmons reaction of the obtained adducts with formaldehyde. Stereochemistry of the intermediate Michael adducts is also discussed. Final 5-methylidenetetrahydropyran-4-ones were tested for their possible antiproliferative effect against three cancer cell lines and 6-isopropyl-2,2-dimethyl-5-methylidenetetrahydropyran-4-one (11c), which showed very high cytotoxic activity against HL-60 human leukemia cells and was three times more active than known anticancer drug carboplatin, was selected for further biological evaluation, in order to disclose its mechanism of action. The obtained results indicated that 11c induced apoptosis in HL-60 cells and caused the arrest of the cell cycle in the G2/M phase, which may suggest its cytotoxic and cytostatic activity.

Macozinone: revised synthesis and crystal structure of a promising new drug for treating drug-sensitive and drug-resistant tuberculosis

Mycobacterium tuberculosis (Mtb), the principal etiological agent of tuberculosis (TB), infects over one-quarter of humanity and is now the leading cause of infectious disease mortality by a single pathogen. Macozinone {2-[4-(cyclohexylmethyl)piperazin-1-yl]-8-nitro-6-(trifluoromethyl)-4H-1,3-benzothiazin-4-one, C₂₀H₂₃F₃N₄O₃S} is a promising new drug for treating drug-sensitive and drug-resistant TB that has successfully completed phase I clinical trials. We report the complete spectroscopic and structural characterization by ¹H NMR, ¹³C NMR, HRMS, IR, and X-ray crystallography. The cyclohexyl moiety is observed to be nearly perpendicular to the core formed by the 1,3-benzothiazin-4-one and piperazine groups. The central piperazine ring adopts a slightly distorted chair conformation caused by sp²-hybridization of the nitro N atom, which donates into the electron-deficient 1,3-benzothiazin-4-one group.

Synthesis and fluorescence studies of novel bisarylmethylidene derivatives of 2-methoxy-2-methyl-1,3-dioxan-5-one

The first general procedure is described for the synthesis of novel bisarylmethylidenes of 2-methoxy-2-methyl-1,3-dioxan-5-one 1. Thus, several derivatives of 3 are obtained rapidly in high yields by reacting 1 with different aldehydes in the presence of catalytic quantities of pyrrolidine in EtOH at room temperature. Upon completion of the reactions, products are obtained directly by spontaneous precipitation avoiding time consuming and expensive chromatographic separations. All products were characterized by proton and carbon NMR spectroscopy methods, and in one case, the proposed structure was elucidated by X-ray crystallography, confirming the Z stereochemistry for the olefinic C=C bonds. Due to showing different colours in solid and solution states, products were studied for their photophysical properties as well.

Pyrrolidine-mediated direct preparation of (e)-monoarylidene derivatives of homo- and heterocyclic ketones with various aldehydes

An efficient method for the facile synthesis of (E)-monoarylidene derivatives of homo- and heterocyclic ketones with various aldehydes in the presence of a pyrrolidine organocatalyst has been achieved. A range of α,β-unsaturated ketones were obtained in moderate to high yields (up to 99%). Unlike the Claisen-Schmidt condensation process, the formation of undesired bisarylidene byproducts is not observed. The possible reaction mechanism suggests that the reaction proceeds via a Mannich-elimination sequence.

Ultrasound mediation for efficient synthesis of monoarylidene derivatives of homo- and heterocyclic ketones

Ultrasonic irradiation was efficiently used for high yield synthesis of monoarylidene derivatives of cyclic systems directly from the reaction of ketone with various aldehydes under solvent-free conditions. Reactions took place rapidly in the presence of catalytic amounts of pyrrolidine, while no significant formation of the undesired bis by-products was observed. Moreover, the procedure was applicable to both homo- and heterocyclic ketones.