NHC-catalyzed generation of difluorocarbene and its application to difluoromethylation of oxygen nucleophiles

Controlled generation of difluorocarbene was effected by an NHC catalyst under mild conditions starting from trimethylsilyl 2,2-difluoro-2-fluorosulfonylacetate (TFDA). Cyclohexenones and tetralones were treated with TFDA in the presence of catalytic amounts of N,N′-dimesitylimidazolium chloride and sodium carbonate. The ketones were difluoromethylated with the generated difluorocarbene to afford enol difluoromethyl ethers without difluorocyclopropanation. The ethers thus obtained were dehydrogenated with DDQ to furnish aryl difluoromethyl ethers in high yield. Under similar conditions, secondary amides underwent difluoromethylation selectively on the oxygen atom to give difluoromethyl imidates, which allows the formation of 2-difluoromethoxypyridines.     

New synthesis of multisubstituted cyanocyclopropanes by the intramolecular SN2 alkylation and 1,3-CC insertion reaction of magnesium carbenoids as the key reactions

Addition reaction of 1-chlorovinyl p-tolyl sulfoxides derived from ketones and aldehydes with lithium α-cyano carbanions gave nitrile adducts in high to quantitative yields. Treatment of the nitrile adducts derived from acetonitrile with excess i-PrMgCl in THF resulted in the formation of cyanocyclopropanes via the intramolecular S_N2 alkylation of the generated magnesium carbenoids. The intermediate of this reaction was proved to be a cyclopropylmagnesium chloride and was reactive with electrophiles to give multisubstituted cyanocyclopropanes. On the other hand, the reaction of the nitrile adducts derived from arylacetonitriles with i-PrMgCl resulted in the formation of 2-arylcyanocyclopropanes by the 1,3-carbon–carbon (1,3-CC) insertion reaction of the generated magnesium carbenoid intermediates. This reaction was found to proceed in a highly stereospecific manner. The key reactions, intramolecular S_N2 alkylation and 1,3-CC insertion reaction of the magnesium carbenoids, are the first examples for the reaction of the magnesium carbenoids bearing a nitrile functional group.     

Synthesis and evaluation of N-phenyl-(2-aminothiazol-4-yl)acetamides with phenoxypropanolamine moiety as selective β3-adrenergic receptor agonists

In the search for potent and selective human β3-adrenergic receptor (AR) agonists as potential drugs for use in treating obesity and non-insulin dependent (type 2) diabetes, a series of N-phenyl-(2-aminothiazol-4-yl)acetamides with phenoxypropanolamine moiety were prepared and their biological activities against human β3-, β2-, and β1-ARs were evaluated. Among these compounds, N-phenyl-(2-phenylaminothiazol-4-yl)acetamide (4 g), N-phenyl-(2-benzylaminothiazol-4-yl)acetamide (4j), and N-phenyl-[2-(3-methoxyphenyl)aminothiazol-4-yl]acetamide (6g) derivatives showed potent agonistic activity against the β3-AR with functional selectivity over the β1- and β2-ARs. In addition, these compounds exhibited significant hypoglycemic activity in a rodent model of diabetes.     

Flag graphs and their applications in mathematical chemistry for benzenoids

Flag graphs have been used in the past for describing maps on closed surfaces. In this paper we use them for the first time in mathematical chemistry for describing benzenoids and some other similar structures. Examples include catacondensed and pericondensed benzenoids. Several theorems are included. Symmetries of benzenoid systems, flag graphs, and symmetry type graphs are briefly discussed.     

Total Synthesis of Aspercyclides A and B via Intramolecular Oxidative Diaryl Ether Formation

A highly efficient total synthesis of the 11-membered cyclic aspercyclides A (1) and B (2) has been achieved by chemo- and regioselective intramolecular oxidative C-O bond formation from differently substituted diphenols.     

Stereoselective synthesis of cis-2,5-disubstituted THFs: application to adjacent bis-THF cores of Annonaceous acetogenins

The iodocyclization of γ,δ-unsaturated alcohols in the presence of a silyl enol ether produced cis-2,5-disubstituted tetrahydrofurans in one pot via siloxy intermediates. N-Iodosuccinimide (NIS) effectively worked as an activator of the double bonds in the substrates and the silyl enol ether. Application to an expedient synthesis of the adjacent bis-tetrahydrofuran core of Annonaceous acetogenins with a cis/threo/cis relative stereochemistry is also described.     

Sevenfold enhancement on porphyrin dye efficiency by coordination of ruthenium polypyridine complexes

Sevenfold enhancement of photoconversion efficiency was achieved by incorporation of peripheral ruthenium complexes to a porphyrin dye, generating supramolecular effects capable of playing several key roles (e.g., transferring energy to, inhibiting aggregation, and accepting the hole generated in the porphyrin center after electron injection), providing new insights for the design of better DSSC photosensitizers.     

Thermal and structural properties of surfactant–picrate compounds

The novel surfactant?Cpicrate compounds were synthesized and characterized by thermal and XRD analysis. The synthesis, based on the electrostatic interactions of components in polar solvents, was carried out using picric acid and cationic surfactants (dodecyltrimethylammonium, didodecyldimethylammonium, and tridodecylmethylammonium halide). The idea was to investigate the dependence of physico-chemical properties and thermal transitions of picrate?Csurfactant compounds with raising number of dodecyl chains sited on the same ammoniumm head group. The equimolar mixed aqueous solutions are characterized as lyotropic, strongly promoted by picrate anion. The main crystal structure feature of investigated picrates is layered structure with stacked aromatic rings of one picrate molecule on the top of the other one via strong ?С??? interactions and connection to the alkylammonium molecules with their nitro groups by C?CH??O hydrogen bonds. Surfactant?Cpicrate bilayer-like structures are interrupted with layers of polar heads and picrate counterions and the observed width of such a bilayers are functions of more complex structural behaviors which ensures alternation in space of equal numbers of positive and negative charges. Although some of the surfactants used posses thermotropic porperties, like examined tridodecylmethylammonium chloride, no thermotropic mesomorphism is detected in solid state of investigated surfactant?Cpicrate compounds. The thermodynamic parameters of solid?Cliquid thermal transitions depend linear on the number of dodecyl chains, and for double- and triple-tailed picrate compounds the marked temporal hysteresis of the melt crystallization is registered.