A New One-dimensional Dicyanamide Bridged Zinc(II) Complex Containing Nitronyl Nitroxide Radicals:Synthesis,Crystal Structure and Magnetic Properties

A new one-dimensional dicyanamide bridged zinc(II) complex containing nitronyl nitroxide radicals Zn(NO3)(NIT-1'-MeBzIm)(dca)n·(H2O)n(NIT-1'-MeBzIm = 2-{2'-(l'-me-thyl)benzimidazolyl}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, dca = dicyanamide anion) has been prepared and structurally characterized by single-crystal X-ray diffraction.The complex crystallizes in triclinic, space group P1, with a = 7.428(3), b = 9.839(3), c = 16.708(6), α = 93.270(4), β = 101.642(4), γ = 100.632(4)°, C17.5H21N8O5.5Zn, Mr = 496.79, V = 1169.7(7) 3, Dc = 1.411 g/cm3, μ(MoKα) = 1.096 mm-1, Z = 2, F(000) = 512, R = 0.0583 and wR = 0.1663 for 4295 observed reflections with I > 2σ(I).X-ray analysis reveals that the zinc(II) ion is six-coordinated with a distorted octahedral geometry.These units develop as 1D species where dicyanamide ligands bridge zinc(II) ions.In addition, molecules are linked by π-π piling interactions to form 1-D double-chains.Magnetic investigation indicates that the weak intramolecular interactions are antiferromagnetic with J =-0.27 cm?1, where the spin Hamitonian is defined as H =-2∑i,jJi,jSiS within the complex.     

Extremely Active Organocatalysts Enable a Highly Enantioselective Addition of Allyltrimethylsilane to Aldehydes

The enantioselective allylation of aldehydes to form homoallylic alcohols is one of the most frequently used carbon–carbon bond‐forming reaction in chemical synthesis and, for several decades, has been a testing ground for new asymmetric methodology. However, a general and highly enantioselective catalytic addition of the inexpensive, nontoxic, air‐ and moisture‐stable allyltrimethylsilane to aldehydes, the Hosomi–Sakurai 1 reaction, has remained elusive. 2 , 3 Reported herein is the design and synthesis of a highly acidic imidodiphosphorimidate motif (IDPi), which enables this transformation, thus converting various aldehydes with aromatic and aliphatic groups at catalyst loadings ranging from 0.05 to 2.0 mol % with excellent enantioselectivities. Our rationally constructed catalysts feature a highly tunable active site, and selectively process small substrates, thus promising utility in various other challenging chemical reactions.     

Acetoxy Meldrum's acid: a versatile acyl anion equivalent in the Pd-catalyzed asymmetric allylic alkylation

Acetoxy Meldrum's acid can serve as a versatile acyl anion equivalent in the Pd-catalyzed asymmetric allylic alkylation. The reaction of this nucleophile with various meso and racemic electrophiles afforded alkylated products in high yields and enantiopurities. These enantioenriched products are versatile intermediates that can be further functionalized using nitrogen- and oxygen-centered nucleophiles, affording versatile scaffolds for the synthesis of nucleoside analogues. These scaffolds were used to complete formal syntheses of the anti-HIV drugs carbovir, abacavir, and the antibiotic aristeromycin.     

Effects of Temperature Raising Speed on the Growth of BN Crystals in Hydrothermal Solutions

Cubic boron nitride (cBN) and orthorhombic boron nitride (oBN) crystals have been prepared in hydrothermal solutions by reacting H3BO3 NaN3 P and H3BO3 NaN3 N2H4 respectively. The experimental results indicated that, if the temperature was increased rapidly, both the yield and perfectness of BN crystals became poor. On the contrast, the yield and perfectness of BN crystals can be improved very much by slowly increasing the temperature of the reaction mixture. The results of X-ray powder diffraction (XRD), Fourier transform infrared spectrum (FTIR) and high resolution transmission electron microscopy (HRTEM) proved that the samples were composed of oBN and cBN.     

The Catalytic Asymmetric α‐Benzylation of Aldehydes

The first aminocatalyzed α‐alkylation of α‐branched aldehydes with benzyl bromides as alkylating agents has been developed. Using a sterically demanding proline derived catalyst, racemic α‐branched aldehydes are reacted with alkylating agents in a DYKAT process to give the corresponding α‐alkylated aldehydes with quaternary stereogenic centers in good yields and high enantioselectivities.