Microfluidics: from dynamic lattices to periodic arrays of polymer disks

We used coupling of flow and geometric confinement to assemble emulsion droplets in two-dimensional gliding lattices with a high degree of order and symmetry. Highly monodisperse discoid droplets with circular shapes were generated in a microfluidic flow-focusing device. Originally, close-packed lattices formed from these circular discoid droplets. Progressive confinement led to the gradual deformation of the circular disks: first, they elongated in the direction parallel to the direction of flow and then transformed into hexagons. Assembly driven by the combination of flow and confinement also allowed for the formation of lattices from droplets with a bimodal size distribution. We used photopolymerization of the monomer droplets to trap the lattice structure in the solid state and produce highly periodic arrays of solid polymer disks.     

The Mitsunobu Reaction: Origin,Mechanism, Improvements,and Applications

The Mitsunobu reaction is a widely used and versatile method for the dehydrative oxidation–reduction condensation of an acid/pronucleophile usually with a primary or secondary alcohol that requires the combination of a reducing phosphine reagent together with an oxidizing azo reagent. The utility of this reaction stems from the fact that it is generally highly stereoselective and occurs with inversion of the stereochemical configuration of the alcohol starting material. Furthermore, as carboxylic acids, phenols, imides, sulfonamides, and other compounds can be used as the acid/pronucleophile, this reaction is useful for the preparation of a wide variety of functional groups. This Focus Review of the Mitsunobu reaction summarizes its origins, the current understanding of its mechanism, and recent improvements and applications.     

3‐Methylamido‐3′,4′‐ethyl­enedithiotetra­thia­fulvalene­(+) potassium tetra­isothio­cyanato­mercury(II)

In the title compound, (C₁₀H₉NOS₆)K[Hg(SCN)₄] or (EDT–TTF–CONHMe)K[Hg(SCN)₄)], fully oxidized organic (EDT–TTF–CONHMe)^+· radical cations form quasi‐one‐dimensional stacks running along the monoclinic 2₁ axis and alternating along the crystallographic [101] direction with inorganic anion stacks made from mixed K⁺–[Hg(SCN)₄]²⁻ ribbons. For each anion, three essentially collinear SCN ligands inter­act with the K⁺ ions via short N⋯K contacts, while the terminal N atom of the fourth SCN group is engaged in a number of hydrogen‐bond contacts with the –CH, –NH and –CH₂ hydrogen‐bond donors of the amide function. Radical cations are dimerized along the stacks and the crystal conductivity is activated.     

Identification de stérols à chaîne latérale oxygénée dans une éponge de l'espèce Hyrtios

Thirty-two sterols are identified in the sponge Hyrtios sp. In addition to fourteen monohydroxylated compounds, the sterol fraction contains eight functionalized sidechain sterols, three of them new: 3 β-hydroxy-24-norchol-5-en-23-al (19) , (22-trans)-3 β-hydroxycholest-5, 22-dien-24-one (20) and (22R, 23R, 24S) or (22S, 23S, 24S)- 22,23-epoxy-24-methylchoest-5-en-3 β-ol (24). The probable biological origin, rather than artifact production, of these undescribed components is discussed.     

Asymmetric synthesis of functionalized trans-2,6-disubstituted piperidines with N-sulfinyl delta-amino beta-ketoesters. Synthesis of (-)-lasubine I

[reaction: see text] The hydroxy-directed reduction of 1,2-dehydropiperidines with the "ate" complex of DIBAL-H and n-BuLi affords functionalized trans-2,6-disubstituted piperidines. This methodology was employed in the asymmetric synthesis of the quinolizidine alkaloid (-)-lasubine I.     

Molecular recognition for stable organic radicals--2-(6-uradinyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl

Stable radical 2-(6-uradinyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl shows antiferromagnetic spin pairing with 2J/k= -14 K, attributable to a close contact between unpaired spin density on the imidazole-type nitrogen atoms; hydrogen bonds aid dimer formation, but do not appear to play an eletronic role in the magnetic behaviour.     

Aggregation of [Cu(II)4] building blocks into [Cu(II)8] clusters or a [Cu(II)4]infinity chain through subtle chemical control

Coordination complexes of the ligand H3L [1,3-bis(3-oxo-3-phenylpropionyl)-2-hydroxy-5-methylbenzene] with Cu(II) are reported. Clusters showing various nuclearities or modes of supramolecular organization have been prepared by slightly changing the reaction conditions and have been crystallographically characterized. The reaction of H3L with one equivalent of Cu(OAc)2 in DMF yields the dinuclear complex [Cu2(HL)2(dmf)2] (1). Reaction in MeOH of H3L with an increased amount of metal, in the form of Cu(NO3)2, and excess strong base (nBu4NOH) affords the cluster [Cu8(L)2(OMe)8(NO3)2] (2). Complex 2 is a dimer of two linear [Cu4] arrays bridged by methoxide ligands, where the polynucleating ligand is fully deprotonated. The [Cu4]2 clusters are linked to each other by NO3- bridges to form one-dimensional coordination polymers. The link between [Cu8] units and their relative spatial positioning can be modified by changing the anion of the Cu(II) salt, as demonstrated by the synthesis of the cluster polymers [Cu8(L)2(OMe)8Cl2] (3) and [Cu8(L)(OMe)7.86Br2.14] (4), where only NO3- has been replaced by Cl- or Br-, respectively. Similarly, when ClO4- is used, compound [Cu8(L)2(OMe)8(ClO4)2(MeOH)4] (5) can be isolated. It contains independent [Cu8] units. A slight change in the stoichiometry of the reaction leading to 2 affords the related complex catena-[Cu4(L)(OMe)3(NO3)2(H2O)0.36] (6). This polymer contains essentially the same [Cu4] moiety as 2, albeit organized in a completely different arrangement. Each [Cu4] unit in 6 is linked by OMe- ligands to two such equivalent groups to form an infinite chain. Magnetic susceptibility measurements reveal weak antiferromagnetic exchange between Cu(II) centers in 1 (J = -0.73 cm(-1)) and strong antiferromagnetic coupling within [Cu4] chains in 2, 5, and 6 (most negative J values of -113.8 and -177.3 cm(-1) for 2 and 6, respectively).     

Novel carbohydrate-appended metal complexes for potential use in molecular imaging

Seven discrete sugar-pendant diamines were complexed to the {M(CO)(3)}(+) ((99m)Tc/Re) core: 1,3-diamino-2-propyl beta-D-glucopyranoside (L(1)), 1,3-diamino-2-propyl beta-D-xylopyranoside (L(2)), 1,3-diamino-2-propyl alpha-D-mannopyranoside (L(3)), 1,3-diamino-2-propyl alpha-D-galactopyranoside (L(4)), 1,3-diamino-2-propyl beta-D-galactopyranoside (L(5)), 1,3-diamino-2-propyl beta-(alpha-D-glucopyranosyl-(1,4)-D-glucopyranoside) (L(6)), and bis(aminomethyl)bis[(beta-D-glucopyranosyloxy)methyl]methane (L(7)). The Re complexes [Re(L(1)-L(7))(Br)(CO)(3)] were characterized by (1)H and (13)C 1D/2D NMR spectroscopy which confirmed the pendant nature of the carbohydrate moieties in solution. Additional characterization was provided by IR spectroscopy, elemental analysis, and mass spectrometry. Two analogues, [Re(L(2))(CO)(3)Br] and [Re(L(3))(CO)(3)Br], were characterized in the solid state by X-ray crystallography and represent the first reported structures of Re organometallic carbohydrate compounds. Conductivity measurements in H(2)O established that the complexes exist as [Re(L(1)-L(7))(H(2)O)(CO)(3)]Br in aqueous conditions. Radiolabelling of L(1)-L(7) with [(99m)Tc(H(2)O)(3)(CO)(3)](+) afforded in high yield compounds of identical character to the Re analogues. The radiolabelled compounds were determined to exhibit high in vitro stability towards ligand exchange in the presence of an excess of either cysteine or histidine over a 24 h period.     

Synthesis and molecular and extended structures for a diaminonaphthalene-derived bis(amido)stannylene

The cyclic bis(amido)tin(II) compound Sn[1,8-((iPrN)2C10H6] (2) was isolated from the reaction of Li2[1,8-((iPrN)2C10H6] (1) and SnCl2. Solid-state structural analysis of 2 showed it to be a mononuclear species with a pyramidal Sn center as part of a nonplanar metallaheterocycle. The packing diagram of 2 revealed an extended one-dimensional head-to-tail chain structure with short intermolecular Sn/arene-C interactions. Computational examination of 2 (DFT/PW91 and MP2 with 6-31G* and 6-311G** basis functions) indicated that the optimum gas-phase structure of 2,which displays a Sn center in the plane of the naphthyl backbone with a slightly twisted metallaheterocycle, is approximately 24 kcal/mol lower in energy than the X-ray structure. The solid-state geometry of 2 is attributed to the intermolecular donation of the naphthalene pi-electrons to a Lewis acidic Sn center, which leads to the observed supramolecular structure. The crystal structure of 1 is also reported.     

Catalytic asymmetric vinylation of ketones

This communication describes the catalytic asymmetric 1,2-addition of vinylzinc reagents to aromatic, alpha,beta-unsaturated, and dialkyl ketones with enantioselectivities between 79 and 97% and with yields ranging from 84 to 98%. The products of these reactions are tertiary allylic alcohols with chiral quaternary centers that are useful in organic synthesis. The reaction involves hydrozirconation of a terminal alkyne, transmetalation to zinc, and addition to a ketone in the presence of a chiral titanium-based Lewis acid catalyst. The reactions proceed smoothly at room temperature in under 24 h.