An efficient procedure for the preparation of (E)-alpha-alkylidenecycloalkanones mediated by a CeCl(3) x 7H(2)O-NaI system. Novel methodology for the synthesis of (S)-(-)-pulegone

Toward a Chemical Constructor: A Lego-Like Approach for Formal α-Alkylation of Cyclic Ketones

A conceptual strategy for a formal α-alkylation of α-methylene ketones was developed. Diverse 1° and 2° alkyl substituents were generated in the α-position of various ketones via synthesis of enaminone (step 1) and treatment with organomagnesium (step 2) with subsequent catalytic hydrogenation (step 3, 1° alkyl) or organocopper reagents (step 4, 2° alkyl). Tolerance toward ester, Boc-protected amine, and α-fluoro-substituted ketone moieties was demonstrated. The suitability of the method for late-stage natural product modification was shown.

CeCl3·7H2O–NaI/SiO2 promoted Beckmann rearrangement (under solvent-free and microwave irradiation)

CeCl3·7H2O–NaI/SiO2 system promoted Beckmann rearrangement of a variety of aldoximes and ketoximes was efficiently conducted under solvent-free and microwave irradiation conditions. This protocol afforded an alternative method for the preparation of amides by Beckmann rearrangement with advantages of short reaction time, high yield, no pollution, simple operation and easy work-up.

Calamintha nepeta (L.) Savi and its Main Essential Oil Constituent Pulegone: Biological Activities and Chemistry

Medicinal plants play an important role in the treatment of a wide range of diseases, even if their chemical constituents are not always completely recognized. Observations on their use and efficacy significantly contribute to the disclosure of their therapeutic properties. Calamintha nepeta (L.) Savi is an aromatic herb with a mint-oregano flavor, used in the Mediterranean areas as a traditional medicine. It has an extensive range of biological activities, including antimicrobial, antioxidant and anti-inflammatory, as well as anti-ulcer and insecticidal properties. This study aims to review the scientific findings and research reported to date on Calamintha nepeta (L.) Savi that prove many of the remarkable various biological actions, effects and some uses of this species as a source of bioactive natural compounds. On the other hand, pulegone, the major chemical constituent of Calamintha nepeta (L.) Savi essential oil, has been reported to exhibit numerous bioactivities in cells and animals. Thus, this integrated overview also surveys and interprets the present knowledge of chemistry and analysis of this oxygenated monoterpene, as well as its beneficial bioactivities. Areas for future research are suggested.

Synthesis of (+)-Ipalbidine Based on 6-exo-trig Radical Cyclization of a β-Amino Radical

N-Boc (S)-proline was converted into (2S)-2-[(phenylselanyl)methyl]pyrrolidine, which was alkylated on nitrogen with 2-bromo-1-(4-methoxyphenyl)ethan-1-one. Reaction with vinyllithium, 6-exo-trig radical cyclization (Bu3SnH, AIBN, PhMe, 110 °C), dehydration (P2O5, H3PO4), and demethylation (BBr3) gave (+)-ipalbidine with ee >99%.

Design, synthesis, and antiviral activity evaluation of phenanthrene-based antofine derivatives

On the basis of our previous structure-activity relationship (SAR) and antiviral mechanism studies, a series of phenanthrene-based antofine derivatives (1-12 and 18-50) were designed targeting tobacco mosaic virus (TMV) RNA and synthesized and systematically evaluated for their antiviral activity against TMV. The bioassay results showed that most of these compounds exhibited good to excellent in vivo anti-TMV activity, of which compounds 19 and 27 displayed higher activity than commercial Ribavirin, thus emerging as potential inhibitors of plant virus. The novel concise structure provides another new template for antiviral studies.

Chiral aminophosphines as catalysts for enantioselective double-Michael indoline syntheses

The bisphosphine-catalyzed double-Michael addition of dinucleophiles to electron-deficient acetylenes is an efficient process for the synthesis of many nitrogen-containing heterocycles. Because the resulting heterocycles contain at least one stereogenic center, this double-Michael reaction would be even more useful if an asymmetric variant of the reaction were to be developed. Aminophosphines can also facilitate the double-Michael reaction and chiral amines are more readily available in Nature and synthetically; therefore, in this study we prepared several new chiral aminophosphines. When employed in the asymmetric double-Michael reaction between ortho-tosylamidophenyl malonate and 3-butyn-2-one, the chiral aminophosphines produced indolines in excellent yields with moderate asymmetric induction.

New chiral P-N ligands for the regio- and stereoselective Pd-catalyzed dimerization of styrene

Two new chiral, enantiomerically pure, hybrid P-N ligands, namely (2R,5S)-2-phenyl-3-(2-pyridyl)-1,3-diaza-2-phosphanicyclo[3,3,0]octan-4-one (1) and (2R,5S)-2-phenyl-3-(2-pyridyl)-1,3-diaza-2-phosphanicyclo[3,3,0]octane (2), have been synthesized starting from L-proline. The two ligands differ in the presence or not of a carbonyl group in the diazaphosphane ring. Their coordination chemistry towards Pd(II) was studied by reacting them with [Pd(CH₃)Cl(cod)]. A different behaviour was observed: ligand 2 shows the expected bidentate chelating behaviour leading to the mononuclear Pd-complex, while ligand 1 acts as a terdentate ligand giving a dinuclear species. The corresponding cationic derivatives were obtained from the palladium neutral complexes, both as mono- and dinuclear derivatives, and tested as precatalysts for styrene dimerization, yielding E-1,3-diphenyl-1-butene regio- and stereoselectively as the sole product. A detailed analysis of the catalytic behaviour is reported.

Enantioselective α-Chlorination of Aldehydes with Recyclable Fluorous (S)-Pyrrolidine-Thiourea Bifunctional Organocatalyst

A novel fluorous (S)-pyrrolidine-thiourea bifunctional organocatalyst is prepared. The catalyst shows good activity and enantioselectivity for direct α-chlorination of aldehydes using N-chlorosuccinimide (NCS) as the chlorine source. It can be recovered from the reaction mixture by fluorous solid-phase extraction with excellent purity for direct reuse.

Enantioselective and diastereoselective Michael addition of ketone/aldehyde totrans-nitroolefins catalyzed by a novel chiral pyrrolidine-thiourea

The direct Michael addition reaction of cyclohexanone/aliphatic aldehydes with nitroolefins, catalyzed by a novel chiral pyrrolidine-thiourea catalyst 1a, is described. The desired 1,4-adducts were obtained in moderate yields with enantioselectivities up to 99% ee and dr up to 99:1 of the syn product.

Enantioselective desymmetrization of prochiral cyclohexanone derivatives via the organocatalytic direct Aldol reaction

Asymmetric desymmetrization of 4-substituted cyclohexanones using proline amide-catalyzed direct aldol reaction afforded beta-hydroxyketones with three stereogenic centers in high enantioselectivities of up to >99% ee.

The Michael addition of indoles to alpha,beta-unsaturated ketones catalyzed by CeCl3.7H2O-NaI combination supported on silica gel

Alkylation of indoles by means of the Michael addition has been the subject of a number of investigation. It is well established that regioselectivity in the additions of indoles to electron-deficient alkenes is strongly controlled by the reaction medium. In a continuation of the work on developing greener and cleaner technologies, the cerium(III) chloride heptahydrate and sodium iodide combination supported on silica gel catalyzes the alkylation of various indoles with alpha,beta-unsaturated ketones giving 3-(3-oxoalkyl)indole derivatives in good yields. The substitution on the indole nucleus occurred exclusively at the 3-position, and N-alkylation products have not been observed.