CAAC‐Based Thiele and Schlenk Hydrocarbons

Diradicals have been of tremendous interest for over a century ever since the first reports of p‐ and m‐phenylene‐bridged diphenylmethylradicals in 1904 by Thiele and 1915 by Schlenk. Reported here are the first examples of cyclic(alkyl)(amino)carbene (CAAC) analogues of Thiele's hydrocarbon, a Kekulé diradical, and Schlenk's hydrocarbon, a non‐Kekulé diradical, without using CAAC as a precursor. The CAAC analogue of Thiele's hydrocarbon has a singlet ground state, whereas the CAAC analogue of Schlenk's hydrocarbon contains two unpaired electrons. The latter forms a dimer, by an intermolecular double head‐to‐tail dimerization. This straightforward synthetic methodology is modular and can be extended for the generation of redox‐active organic compounds.     

A Stable Homoleptic Organometallic Iron(IV) Complex

A homoleptic organometallic Fe^IV complex that is stable in both solution and in the solid state at ambient conditions has been synthesized and isolated as [Fe(phtmeimb)₂](PF₆)₂ (phtmeimb=[phenyl(tris(3-methylimidazolin-2-ylidene))borate]⁻). This Fe^IV N-heterocyclic carbene (NHC) complex was characterized by ¹H NMR, HR-MS, elemental analysis, scXRD analysis, electrochemistry, Mößbauer spectroscopy, and magnetic susceptibility. The two latter techniques unequivocally demonstrate that [Fe(phtmeimb)₂](PF₆)₂ is a triplet Fe^IV low-spin S=1 complex in the ground state, in agreement with quantum chemical calculations. The electronic absorption spectrum of [Fe(phtmeimb)₂](PF₆)₂ in acetonitrile shows an intense absorption band in the red and near IR, due to LMCT (ligand-to-metal charge transfer) excitation. For the first time the excited state dynamics of a Fe^IV complex was studied and revealed a ≈0.8 ps lifetime of the ³LMCT excited state of [Fe(phtmeimb)₂](PF₆)₂ in acetonitrile.     

In Vitro Plant Propagation of Catharanthus roseus and Assessment of Genetic Fidelity of Micropropagated Plants by RAPD Marker Assay

An investigation was carried out to develop an efficient micropropagation protocol for Catharanthus roseus. Experiments were conducted to optimize suitable media for in vitro shoot multiplication and root induction. Out of the different media compared for in vitro shoot multiplication, Murashige and Skoog (MS) medium supplemented with 1 mg/l of 6-benzylaminopurine and 0.2 mg/l α-naphthaleneacetic acid showed better response in terms of the emergence of shoots from axillary buds as well as proliferation and multiplication of shoots. The shoots when placed on half strength of MS medium having 1 mg/l indole 3-butyric acid and 0.25 % charcoal showed cent percent root induction with maximum number of roots per shoot (4.2) as well as maximum root length (1.72 cm). Further, clonal fidelity of the in vitro-raised plants was carried out using randomly amplified polymorphic DNA marker and results indicated that all the tissue culture-derived plants are true-to-type and there were no somaclonal variations among these plants.     

The lithiation of 2-chloroglucal derivatives

Lithiation of 2-chloroglucal derivatives provides ready access to the corresponding 1-lithioglucals which undergo a variety of serve useful intermediates for further elaboration of the carbohydrate nucleus. Removal of the 2-chloro substituent may be affected using a Birch-type reduction.     

Effect of Four-Wave Mixing on Optimal Placement of Optical Amplifier in WDM Star Networks

In this article, the effect of four-wave mixing (FWM) and amplified spontaneous emission (ASE) noise on WDM optical star networks has been investigated. Analysis for the evaluation of probability of error has been carried out (a) when only FWM is present and (b) when both FWM and ASE noise are present. Numerical results are presented in the graphical and tabular forms for the practical values of parameters. Finally, optimal location of the amplifier in the network has been identified as being before the star coupler preceding the receiver.     

Influence of a reversible addition–fragmentation chain transfer agent in the dispersion polymerization of styrene

Dispersion polymerization was applied to the controlled/living free‐radical polymerization of styrene with a reversible addition–fragmentation chain transfer (RAFT) polymerization agent in the presence of poly(N‐vinylpyrrolidone) and 2,2′‐azobisisobutyronitrile in an ethanol medium. The effects of the polymerization temperature and the postaddition of RAFT on the polymerization kinetics, molecular weight, polydispersity index (PDI), particle size, and particle size distribution were investigated. The polymerization was strongly dependent on both the temperature and postaddition of RAFT, and typical living behavior was observed when a low PDI was obtained with a linearly increased molecular weight. The rate of polymerization, molecular weight, and PDI, as well as the final particle size, decreased with an increased amount of the RAFT agent in comparison with those of traditional dispersion polymerization. Thus, the results suggest that the RAFT agent plays an important role in the dispersion polymerization of styrene, not only reducing the PDI from 3.34 to 1.28 but also producing monodisperse polystyrene microspheres. This appears to be the first instance in which a living character has been demonstrated in a RAFT‐mediated dispersion polymerization of styrene while the colloidal stability is maintained in comparison with conventional dispersion polymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 348–360, 2007     

Lithium Tetrafluoroborate–Catalyzed Solventless Synthesis of α-Aminonitriles

Lithium tetrafluoroborate-catalyzed one-pot, highly efficient, and solvent-free protocol has been developed for the synthesis of α-aminonitriles from aldehydes/ketones, amines, and trimethylsilyl cyanide.     

Microwave-mediated reductive amination-cyclization of 4-aryl-4-oxobutanoates: Facile synthesis of 3-methylidene-5-phenyl-2,3-dihydropyrrolidones

Microwave-mediated three-component condensation of 4-aryl-4-oxobutanoates with ammonium formate furnishes 3-methylidene-5-phenyl-2,3-dihydropyrrolidones in good yield within 2 min. The pyrrolidone products were characterized on the basis of spectral data and X-ray crystal structure analysis. The reaction is found to be general and a variation in the ester and aryl moieties is possible. However, when alkylammonium formate is used only amide products are formed     

Chemistry of superacids

Superelectrophilic nitration of deactivated aromatics with NO₂Cl−3MX _n complexes in aprotic nonpolar solvents such as CH₂Cl₂ makes it possible to obtain the corresponding nitro derivatives in good to almost quantitative yields under mild conditions. For part 34, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 953–956, May, 1998.