Hydrodealkenylative C(sp3)-C(sp2) bond fragmentation

Chemical synthesis typically relies on reactions that generate complexity through elaboration of simple starting materials. Less common are deconstructive strategies toward complexity-particularly those involving carbon-carbon bond scission. Here, we introduce one such transformation: the hydrodealkenylative cleavage of C(sp³)-C(sp²) bonds, conducted below room temperature, using ozone, an iron salt, and a hydrogen atom donor. These reactions are performed in nonanhydrous solvents and open to the air; reach completion within 30 minutes; and deliver their products in high yields, even on decagram scales. We have used this broadly functionality tolerant transformation to produce desirable synthetic intermediates, many of which are optically active, from abundantly available terpenes and terpenoid-derived precursors. We have also applied it in the formal total syntheses of complex molecules.

Synthetic analogues of marine cytotoxic jaspine B and its stereoisomers

Synthetic analogues of the cytotoxic jaspine B and its stereochemical congeners have become an attractive target in the synthetic organic community owing to the search for novel therapeutic candidates with more potent anticancer activity, as cancer is the second leading cause of death worldwide. This review article provides insights into the different approaches and strategies available in the literature for the construction of jaspine B-related compounds.

Investigation of copper(II) tetrafluoroborate catalysed epoxide opening

We report the extension of the copper(II) tetrafluoroborate catalysed opening of epoxides with alcohols to include a wider variety of alcohols, a range of solvents and a method to purify the products from the reaction.

Lewis acid organocatalysts

Abstract The term Lewis acid catalysts generally refers to metal salts like aluminium chloride, titanium chloride and zinc chloride. Their application in asymmetric catalysis can be achieved by the addition of enantiopure ligands to these salts. However, not only metal centers can function as Lewis acids. Compounds containing carbenium, silyl or phosphonium cations display Lewis acid catalytic activity. In addition, hypervalent compounds based on phosphorus and silicon, inherit Lewis acidity. Furthermore, ionic liquids, organic salts with a melting point below 100 degrees C, have revealed the ability to catalyze a range of reactions either in substoichiometric amount or, if used as the reaction medium, in stoichiometric or even larger quantities. The ionic liquids can often be efficiently recovered. The catalytic activity of the ionic liquid is explained by the Lewis acidic nature of their cations. This review covers the survey of known classes of metal-free Lewis acids and their application in catalysis.

Photosonochemical catalytic ring opening of alpha-epoxyketones

The combination of ultrasound and photochemical methods has been used for the catalytic ring opening of α-epoxyketones by 1-benzyl-2,4,6-triphenylpyridinium tetrafluoroborate (NBTPT) as photocatalyst in methanol. Sonication of these compounds in the presence of NBTPT did not result in the opening of epoxide ring, but the use of ultrasound increased the rate of photoreaction.

Synthesis of 8-geranyloxypsoralen analogues and their evaluation as inhibitors of CYP3A4

Furanocoumarins have been shown to inhibit CYP3A4 in vitro with varying degrees of potency. In this study, we report the effects of a series of novel furanocoumarins based on the naturally occurring derivative 8-geranylepoxypsoralen which has been shown to be a more potent inhibitor of CYP3A4 than its 5-position-substituted counterpart bergamottin. Compounds were designed, synthesised and tested for their ability to inhibit CYP3A4 activity in human liver microsomes using testosterone as the marker substrate. Both the saturated and unsaturated phenolic furanocoumarin derivatives were found to be inactive. However, the 8-alkyloxy-furanocoumarin analogues were shown to inhibit CYP3A4 activity in a dose dependent manner, with IC(50) values ranging from 0.78+/-0.11 to 3.93+/-0.53 microM. The reduced furan derivative dihydro-8-geranyloxypsoralen showed a 4-fold decrease in inhibitory potency, suggesting that the furan moiety plays a role in the interaction between these compounds and CYP3A4.

Development of Polymer-supported π-Acid Catalysts

We reported that dicyanoketene acetals (DCKA), in which gem-dicyano groups of tetracyanoethylene (TCNE) are displaced with alkoxyl groups, function as pi-acid catalysts, and that a polymer (poly-DCKA-1) derived by copolymerization of a monomer, in which the alkoxyl group at the omega-position is modified with a styrene moiety, with ethyleneglycol dimethacrylate also shows high level of activities as a pi-acid. In this research, the effects of dicyanoketene ethylene acetal (DCKEA), polymers previously developed (poly-DCKA-1 and 2), new monomers, in which the alkoxyl group at the omega-position is modified with an ethereal moiety, and the corresponding polymers (poly-DCKA-3 and 4) were investigated on catalytic activities. Among the catalysts, the polymer (poly-DCKA-1) had the most efficient activity in monothioacetalization, cyanation, and Mukaiyama aldol reaction of acetals, two-component and three-component Mannich-type reaction, hydrolysis of acetals and silyl ethers, and two-component and three-component inverse electron demand Aza-Diels-Alder reaction. Remarkably, the polymer catalyst works more efficiently in water than in organic solvents and is recyclable.

The Dianion of 5-Cyanoiminotetrazoline: C2N62-

Several salts (alkali, Pd(NH(3))(3), and (i)PrNH(2)) of 5-cyanoiminotetrazoline (C(2)N(6)(2-), 5-cyanoiminotetrazolinediide, CIT) were investigated. A full characterization by means of X-ray, Raman, NMR techniques, mass spectrometry, and elemental analysis is presented for the (i)()PrNH(2) (4), Cs (5), and Pd(NH(3))(3) (6) salts. The CIT dianion represents a nitrogen-rich binary CN dianion, and 5 forms monoclinic crystals (a = 7.345(2) Angstroms, b = 9.505(2) Angstroms, c = 10.198(2) Angstroms, beta = 92.12(3) degrees, space group P2(1)/n, Z = 4). DSC and in situ temperature-dependent X-ray diffraction measurements of the cesium salt 5 revealed an astonishing thermal stability accompanied by a reversible phase transition from the low-temperature alpha modification to the metastable beta modification at 253 degrees C. Above the melting point (334 degrees C), the cesium salt decomposes yielding cesium azide and cesium dicyanamide, which decomposes under further heating under release of nitrogen. The reaction of Cs(2)CIT with SO(2) resulted in the surprising formation of a new cesium salt with the 5-cyaniminotetrazoline-1-sulfonate dianion (Cs(2)CITSO(3).SO(2) (7)). 7 crystallizes in the monoclinic space group P2(1) with one SO(2) solvent molecule (a = 8.0080(2) Angstroms, b = 8.0183(2) Angstroms, c = 9.8986(3) Angstroms, beta = 108.619(1) degrees, Z = 2). The structure and bonding of the 10pi dianion are discussed on the basis B3LYP/aug-cc-pvTZ computations (MO, NBO), and the three-dimensional array of the cesium salts with respect to the Cs(delta) (+)-N(delta)(-) in 5 compared to the Cs(delta)(+)-N(delta)(-) and Cs(delta)(+)-O(delta)(-) in 7 is discussed. Due to the expected rich bonding modes of the CIT anions, the coordination chemistry with palladium was also studied, yielding monoclinic crystals of [Pd(CIT)(NH(3))(3)].H(2)O (6, a = 7.988(2) Angstroms, b = 8.375(2) Angstroms, c = 13.541(3) Angstroms, beta = 104.56 degrees, space group P2(1)/n, Z = 4). In the solid state, the complex is composed of dimers, showing two agostic interactions and an unusual close interplanar pi-pi stacking of the tetrazole moiety of the CIT ligand.

Copper(II) tetrafluoroborate catalyzed ring-opening reaction of epoxides with alcohols at room temperature

[reaction: see text] Efficient ring opening of different epoxides by reaction with representative alcohols is presented. These processes were carried out at room temperature and rely on the usefulness of commercial copper tetrafluoroborate as catalyst.

ElectronTransfer Induced Ring Opening of α-Epoxyketones: Spirodioxolane Formation

Stereospecific formation of spirodioxolanes has been observed on electron transfer induced ring opening of α-epoxyketones by 2,4,6-triphenylpyrylium tetrafluoroborate in the presence of cyclohexanone.

Stereoselective synthesis of conformationally constrained cyclohexanediols: a set of molecular scaffolds for the synthesis of glycomimetics

The practical, stereoselective synthesis of the three diastereoisomeric 1,2-trans-dicarboxy-4,5-cyclohexanediols 1-3 (DCCHDs) is described, starting from a common precursor, easily available in both enantiomeric forms. The regioselective derivatization of all functional groups of 1 is also reported. The three DCCHDs are locked in a single chair conformation and thus can be used to mimic vicinally disubstituted monosaccharides of any relative configuration.

Novel rearrangements of sesquiterpenoid panasinsane derivatives under acidic conditions

The sesquiterpenoid panasinsane derivatives 11 and 14-16 have been prepared from caryophyllene oxide (7). The novel rearrangement reactions of compounds 11 and 14 under TCNE-catalyzed solvolysis conditions and the reactions of compounds 15 and 16 under superacid conditions (HSO3F/Et2O, -63 degrees C) have been investigated. The ginsenol derivative 17 is obtained from compounds 11 and 14 under TCNE-catalyzed conditions. The rearrangement of compounds 15 and 16 under superacid conditions leads to the novel sesquiterpene derivatives (1S,4S,7S,10S,11S)-3,3,10,11-tetramethyltricyclo[5.3.1.0(4,10)]undecan-1,11-yl sulfate (19) and (1S,4S,5S,8S)-2,2,4,8-tetramethyl tricyclo[3.3.2.1(4,8)]undecan-11-one (20). The influence of the secondary hydroxyl group at C-5 of the panasinsane derivatives on the course of these rearrangements is discussed.

Novel rearrangement of an isocaryolane sesquiterpenoid under mitsunobu conditions

Under modified Mitsunobu reaction conditions, a novel skeleton rearrangement of terpenes has been obtained. The reactivity of 8, 9-dioxygenated isocaryolane derivatives has been investigated. When either (8R,9R)-8-methoxyisocaryolane-9-ol (7) or (8R, 9R)-isocaryolane-8,9-diol (10) are treated under acidic conditions, isocaryolan-9-one (9) and the rearrangement compound (1S,2S,5R,8S)-1, 4,4-trimethyltricyclo[6.2.1.0(2,5)]undecane-8-carbaldehyde (11) are obtained. Otherwise treatment of compounds 7 and 10 under modified Mitsunobu conditions leads to the novel sesquiterpene derivative (1S, 2S,5R,9R)-1,4,4-trimethyltricyclo[7.2.1.0(2,5)]dodecan-8-one (8). This is the first example, to our knowledge, of a Mitsunobu-induced pinacol rearrangement. The influences of the substrate and reaction conditions on the evolution of the reaction are both explored. This modification of the Mitsunobu reaction conditions introduces a new, one-pot, procedure for preparing this class of rearrangement product.

Cleavage of Protecting Groups Catalysed by π-Acceptors

The cleavage of protecting groups is caused by the acidic adducts produced from the methanolysis of acceptors.