Reversible Insertion of Methyl Isothiocyanate into Copper(I)Aryloxides

MeNCS undergoes insertion into the copper(I)-aryloxide bond to form [N-methylimino(aryloxy)methanethiolato]-copper(I) complexes. This insertion occurs in the absence of ancillary ligands unlike the analogous insertion of PhNCS. The reaction with 4-methylphenoxide results in the formation of hexakis[[N-methylimino(4-methylphenoxy) methanethiolato]copper(I)] (1), which has been characterized by X-ray crystallography. Crystal data for 1: hexagonal , a = 12.365(3) Angstrom, c = 36.734(16) Angstrom, gamma = 120 degrees, Z = 3, V = 4863(3) Angstrom(3), R = 0.0306. Reactions of 2,6-dimethyl- and 4-chlorophenoxides also result in analogous copper(I) complexes 2 and 3. Addition of stochiometric amounts of PPh(3) to the oligomeric complexes typically results in the extrusion of MeNCS. The ease of extrusion is dependent on the substituents on the aryloxide, and this deinsertion is accelerated by water. However, the extrusion reaction is slow enough in the case of the N-methylimino(2,6-dimethylphenoxy)-methanethiolate complex and the isolation of an intermediate monomeric product bis(triphenylphosphine)[N-methylimino(2, 6-dimethylphenoxy)methanethiolato] copper(I) (4) is possible. Crystal data for 4: triclinic , a = 10.088(2) Angstrom, b = 11.302(1) Angstrom, c = 17.990(2) Angstrom, alpha = 94.06(1)degrees, beta = 95.22(2)degrees, gamma = 103.94(1)degrees, Z = 2, V = 1974.4(7) Angstrom(3), R = 0.0361. In the presence of of PPh(3), the insertion reaction becomes reversible. This allows the exchange of the heterocumulene MeNCS or the aryloxy group in these molecules with another heterocumulene or a phenol, respectively, when catalytic amounts of PPh(3) are added. Oligomers with exchanged heterocumulmes and phenols could be characterized by independent synthesis.

Effect of 2-allyl-2-isopropylacetamide on poly(adenylic acid)-containing ribonucleic acid.

A single administration of 2-allyl-2-isopropylacetamide, a porphyrinogenic drug, enhanced the 32P-labelling of nucleoplasmic as well as cytoplasmic poly(A)-containing RNA in rat liver. The synthesis of total microsomal RNA is only marginally increased under these conditions. The drug enhances the labelling of a variety of cytoplasmic poly(A)-containing RNA species, and this effect is counteracted by the simultaneous administration of haemin. 2-Allyl-2-isopropylacetamide also enhanced the release of RNA from the nucleus to the cytoplasm.

Copper(I) promoted C---C bond forming reactions: direct activation of allyl alcohols

Allylic alcohols, acetates, carbonates and chlorides can be activated by copper(I) salts towards nucleophilic substitution by carbon nucleophiles under relatively mild conditions.

Reactions of copper(I) aryloxides with phenyl isothiocyanate: steric and ligand control in the oligomerization of [N-phenylimino(aryloxy)methanethiolato]copper(I) complexes

The preparation of five different copper(I) complexes [CuSC(=NPh)(OAr)}L(n)]m (1-5) formed by the insertion of PhNCS into the Cu-OAr bond and the crystal structure analyses of three of them have been carried out. A monomeric species 1 (OAr = 2,6-dimethylphenoxide) is formed in the presence of excess PPh3 (n = 2, m = 1) and crystallizes as triclinic crystals with a = 12.419(4) angstrom, b = 13.298(7) angstrom, c = 15.936(3) angstrom, alpha = 67.09(3)-degrees, beta = 81.63(2)-degrees, gamma = 66.54(3)-degrees, V = 2224(2) angstrom3, and Z = 2. The structure was refined by the least-squares method to final R and R(w) values of 0.038 and 0.044, respectively, for 7186 unique reflections. Copper(I) 2,5-di-tert-butyl-4-methylphenoxide results in the formation of a dimeric species 2 in the presence of P(OMe)3 (n = 1, m = 2), where the coordination around Cu is trigonal. Crystals of 2 were found to be orthorhombic with a = 15.691(2) angstrom, b = 18.216(3) angstrom, c = 39.198(5) angstrom, v = 11204(3) angstrom3, and Z = 8. Least-squares refinement gave final residuals of R = 0.05 and R(w) = 0.057 with 6866 unique reflections. A tetrameric species 3 results when PPh3 is replaced by P(OMe)3 in the coordination sphere of copper(I) 2,6-dimethylphenoxide. It crystallizes in the space group P1BAR with a = 11.681 (1) angstrom, b = 13.373(2) angstrom, c = 20.127(1) angstrom, a = 88.55(l)-degrees, beta = 89.65(l)-degrees, gamma = 69.28(1)-degrees, V = 2940(l) angstrom3, and Z = 2. Least-squares refinement of the structure gave final values of 0.043 and 0.05 for R and R(w) respectively using 12214 unique reflections. In addition, a dimeric species 4 is formed when 1 equiv of PPh3 is added to the copper(I) 4-methylphenoxide, while with an excess of PPh3 a monomeric species 5 is isolated. Some interconversions among these complexes are also reported.

Thiol-ene Clickable Hyperscaffolds Bearing Peripheral Allyl Groups

Radical catalyzed thiol-ene reaction has become a useful alternative to the Huisgen-type click reaction as it helps to expand the variability in reaction conditions as well as the range of clickable entities. Thus, direct generation of hyper-branched polymers bearing peripheral allyl groups that could be clicked using a variety of functional thiols would be of immense value. A specifically designed AB(2) type monomer, that carries two allyl benzyl ethers groups and one alcohol functionality, was shown to undergo self-condensation under acid-catalyzed melt-transetherification to yield a hyperbranched polyether that carries numerous allyl end-groups. Importantly, it was shown that the kinetics of polymerization is not dramatically affected by the change of the ether unit from previously studied methyl benzyl ether to an allyl benzyl ether. The peripheral allyl groups were readily clicked quantitatively, using a variety of thiols, to generate an hydrocarbon-soluble octadecyl-derivative, amphiphilic systems using 2-mercaptoethanol and chiral amino acid (N-benzoyl cystine) derivatized hyperbranched structures; thus demonstrating the versatility of this novel class of clickable hyperscaffolds. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49:1735-1744, 2011

Cyclopentaannulation of allyl alcohols via a radical cyclisation reaction. Total synthesis of 4-epibakkenolide-A

A four step cyclopentaannulation methodology starting from allyl alcohols using 5-exo-trig radical cyclisation as the key reaction, and its application to the total synthesis of 4-epibakkenolide is described.

Potassamide induced in situ alkylation of 5,6-dihydroisoquinoline with allyl bromide and Michael acceptors

Potassamide induced in situ alkylation of 4-cyano-3-methoxy-1-methyl-5, 6-dihydroisoquinoline (1a) with allyl bromide gives the 5-allyl- and 5,9-diallyl-5,6-dihydroisoquinolines (1c and 1d), isoquinoline derivative 2 and 4-allyl-1, 2, 3, 4-tetrahydroisoquinolin-3(2H)-one (3a). However, potassamide induced in situ alkylation of In with buten-2-one, mesityl oxide and acrylonitrile results in the formation of only 5-alkylated 5,6-dihydroisoquinoline derivatives 1e-g along with fully aromatised compound 2.

Tandem 5-exo-trig allyl and 3-exo-trig radical cyclisation and rearrangement to copa and ylanga type sesquiterpene skeleton

A novel tandem 5-exo-trig allyl and 3-exo-trig radical cyclisation and rearrangement to copa and ylanga type sesquiterpene skeleton is reported.

Mechanistic overview of the curing behavior of hydride terminated polydimethylsiloxane with allyl functionalized alumina by calorimetry and rheometry

The study of the curing behavior of an encapsulation material is very important and critical in terms of understanding the properties of the material. Differential scanning calorimetry and rheometry are two important tools that have been utilized to study curing reactions in polymeric systems. The present work deals with the curing of a mixture of hydride terminated polydimethylsiloxane, allyl functionalized alumina nanoparticles and Karstedt's catalyst. The real time curing behavior of the typical system was monitored non-isothermally by differential scanning calorimetry and rheometry. The results obtained from the respective techniques reveal that there is a good correlation between these two techniques. A mechanism is proposed for the curing reaction of the polymer system based on the curing curves obtained by the above two studies. In addition, the swelling study and contact angle measurement of the two composites was performed to evaluate the extent of cross-linking and hydrophobicity. (C) 2011 Elsevier B.V. All rights reserved.

A non-isothiocyanate route to synthesize trisubstituted thioureas of arylamines using in situ generated dithiocarbamates

A novel, user-friendly, and convenient method for the synthesis of trisubstituted thioureas of arylamines is presented, for the first time, using in situ generated dithiocarbamates of secondary amines. This strategy provides an excellent opportunity to access thioureas containing primary aryl amines. A non-isothiocyanate route to obtain thioureas is the advantage of this strategy, which may provide a useful route to synthesize a variety of biologically active derivatives of thioureas.

A New Tetrahydrofurannulation Via Tandem Radical Cyclization Reaction-Reductive Deoxygenation Sequence

Treatment of bromoketals 2, derived from allyl alcohols 1, with tributyltin chloride, sodium cyanoborohydride and AIBN furnishes the tetrahydrofurannulated products 3 via a 5-exo-trig radical cyclisation reaction followed by reductive cleavage of ketal 4.

A Ca2+-dependent early functional heterogeneity in amoebae of Dictyostelium discoideum, revealed by flow cytometry

When freshly starved amoebae of Dictyostelium discoideum are loaded with the Ca2+-specific dye indo-1/AM and analyzed in a fluorescence-activated cell sorter, they exhibit a quasi-bimodal distribution of fluorescence. This permits a separation of the population into two classes: H, or ''high Ca2+-indo-1 fluorescence,'' and L, or ''low Ca2+-indo-1 fluorescence.'' Simultaneous monitoring of Ca2+-indo-1 and Ca2+-chlortetracycline fluorescence shows that by and large the same cells tend to have high (or low) levels of both cytoplasmic and sequestered Ca2+. Next we label H cells with tetramethylrhodamine isothiocyanate (TRITC) and mix them in a 1:4 ratio with L cells, In the slugs that result, TRITC fluorescence is confined mainly to the anterior prestalk region. This implies that amoebae with relatively high Ca2+ at the vegetative stage tend to develop into prestalk cells and those with low Ca2+ into prespores. Polysphondylium violaceum, a cellular slime mold that does not possess prestalk and prespore cells, also does not display a Ca2+-dependent heterogeneity at the vegetative stage or in slugs. Finally, confirming earlier findings with the fluorophore fura-2 (Azhar ef al., Curr. Sci. 68, 337-342 (1995)), a prestalk-prespore difference in cellular Ca2+ is present in the cells of the slug in vivo. These findings are discussed in light of the possible roles of Ca2+ for cell differentiation in D. discoideum.

Fluorescent labelling of strychnine: A novel approach for recognition of strychnine binding sites on neuronal membrane

trychnine was coupled to fluorescein isothiocyanate to mark strychnine binding sites in spinal cord of rat. Specific binding of strychnine could be demonstrated in synaptosomal fraction. Addition of glycine to the strychninised membrane led to a decrease in fluorescence indicating same receptor loci.

A Theoretical Investigation of the Ni(II)-Catalyzed Hydrovinylation of Styrene

We report a detailed and full computational investigation on the hydrovinylation reaction of styrene with the Ni(II)-phospholane catalytic system, which was originally presumed to proceed through a cationic mechanism involving a nickel hydride intermediate. The following general features emerge from this study on a specific catalyst complex that was found to give quantitative yield and moderate selectivity: (a) the activation barrier for the initiation (18.8 kcal/mol) is higher than that for the reaction due to a low-lying square-planar pentenyl chelate intermediate originating from a Ni(II)-allyl catalyst precursor. Consequently there is an induction period for the catalysis; (b) the exit of product from the catalyst is via a β-H-transfer step instead of the usual β-H elimination pathway, which has a very high activation energy due to a trans effect of the phospholane ligand; (c) the turnover-limiting and enantio- determining transition state is also the β-H-transfer; (d) because of the absence of a hydride intermediate, the unwanted isomerization of the product is prevented; (e) since the enantio-discrimination is decided at the H-transfer stage itself, the configuration of the product in a catalytic cycle influences the enantioselectivity in the subsequent cycle; (f) the trans effect of the sole strong ligand in the d8 square-planar Ni(II), the stability of the η3-benzyl intermediate, and the availability of three coordination sites enable regioselective hydrovinylation over the possible oligomerization/polymerization of the olefin substrates and linear hydrovinylation. This work has also confirmed the previously recognized role of the hemilabile group at various stages in the mechanism.

Primary structure of a Thomsen-Friedenreich-antigen-specific lectin, jacalin [Artocarpus integrifolia (jack fruit) agglutinin]. Evidence for the presence of an internal repeat

Jacalin [Artocarpus integrifolia (jack fruit) agglutinin] is made up of two types of chains, heavy and light, with M(r) values of 16,200 +/- 1200 and 2090 +/- 300 respectively (on the basis of gel-permeation chromatography under denaturing conditions). Its complete amino acid sequence was determined by manual degradation using a 4-dimethylaminoazobenzene 4'-isothiocyanate double-coupling method. Peptide fragments for sequence analysis were obtained by chemical cleavages of the heavy chain with CNBr, hydroxylamine hydrochloride and iodosobenzoic acid and enzymic cleavage with Staphylococcus aureus proteinase. The peptides were purified by a combination gel-permeation and reverse-phase chromatography. The light chains, being only 20 residues long, could be sequenced without fragmentation. Amino acid analyses and carboxypeptidase-Y-digestion C-terminal analyses of the subunits provided supportive evidence for their sequence. Computer-assisted alignment of the jacalin heavy-chain sequence failed to show sequence similarity to that of any lectin for which the complete sequence is known. Analyses of the sequence showed the presence of an internal repeat spanning residues 7-64 and 76-130. The internal repeat was found to be statistically significant.