Hydrogen-bonded mononuclear nickel(II) benzoate complexes: synthesis and structural studies

[Tp^Ph,MeNi(Cl)Pz^Ph,MeH] (1) has been synthesized by the reaction of hydrotris(3-phenyl-5-methyl-pyrazol-1-yl) borate [Tp^Ph,Me], NiCl₂ · 6H₂O and 3-phenyl-5-methyl-pyrazole [Pz^Ph,MeH]. The reaction of 1 with variously substituted sodium p–X–benzoates resulted in the formation of complexes of the type [Tp^Ph,MeNi(p–X–OBz)Pz^Ph,MeH] (X = H for 2, F for 3, Cl for 4, NO₂ for 5, Me for 6, OMe for 7, OH for 8, CHO for 9 and CN for 10). Single crystal X-ray studies suggest that all these complexes have a five-coordinate metal center and the benzoate groups are monodentate in a square pyramidal geometry. The X-ray studies also reveal that the uncoordinated oxygen atom of the benzoate forms intramolecular hydrogen-bonds with the NH group of the coordinated pyrazole. The substituents present on the benzoate ring are involved in different types of intermolecular interactions and the complexes exhibit different crystal packing. Complexes 2–10 were tested for superoxide dismutase activity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Efficient and Rapid Synthesis of Highly Functionalized Novel Symmetric 1,4-Dihydropyridines Using Glacial Acetic Acid as Solvent

A new series of 1,4-dihydropyridines bearing a pyrazole moiety in the 4-position were synthesized by a variation of the classical Hantzsch synthesis. The reaction of 1,3-diphenyl-1H-pyrazole-4-carbaldehyde 4a–n with 3-amino crotononitrile in the presence of glacial acetic acid afforded novel 3,5-dicyano-2,6-dimethyl 1,4-dihydropyridines 5a–n. The procedure has short reaction time (15–20 min), easy workup, and good yield of product. The structures of all synthesized compounds were well characterized by mass, infrared, ¹H and ¹³C NMR, and elemental analysis.     

Structure and packing of aminoxyl and piperidinyl acrylamide monomers

The closely related title compounds, 4‐acrylamido‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl, C₁₂H₂₁N₂O₂, (I), and N‐(2,2,6,6‐tetramethylpiperidin‐4‐yl)acrylamide monohydrate, C₁₂H₂₂N₂O·H₂O, (II), are important monomers in the preparation of redox‐active polymers. They comprise an acrylamide group of the usual s‐cis configuration appended to a 2,2,6,6‐tetramethyl‐substituted piperidine‐1‐oxyl radical or a piperidinyl chair, respectively. The adjacent amide and piperidinyl H atoms are approximately trans across the C—N bond. The packing in (I) is dominated by N—H...O hydrogen bonds; these are supported by C—H...O contacts to form an R₂¹(6) ring repeat, a motif which has been observed in other acrylamide structures. In (II), hydrogen bonds are again key to the packing arrangements. In this case, the incorporated solvent water molecule acts as an acceptor through its O atom and as a donor through both H atoms, binding three adjacent piperidinylacrylamide molecules into layers. In both structures, weak C—H...O contacts involving the piperidinyl methyl H atoms and a proximal acrylamide carbonyl O atom extend the structure in the third dimension.     

Facile one‐pot synthesis of linear and radial block copolymers of styrene and isoprene through a novel coupling agent by living anionic polymerization

A new methodology is successfully used for the concurrent synthesis of three different copolymers; diblock, triblock, and three‐armed star‐block copolymers of styrene and isoprene via the living anionic polymerization with control over the molecular weight and weight fractions of each block. The room temperature polymerization process has resulted in the well defined linear and radial block copolymers, when the living di‐block of poly(styrene‐b‐isoprene) was coupled using cheap and readily available malonyl chloride as a novel coupling agent giving nearly 100% yield. The resulting block copolymers have narrow polydispersity index (PDI = 1.01–1.09) with a good agreement between the calculated and the observed molecular weights. The results are further supported by fractionation of the block copolymers by reversed‐phase temperature gradient interaction chromatography (RP‐TGIC) technique followed by size exclusion chromatography (SEC). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2636–2641, 2010     

Carbonium ion rearrangements controlled by the presence of a silyl group

Tertiary alcohols with a λ-silyl group (3) generally undergo a simple carbonium ion rearrangement in acid giving a single alkene product (4) with loss of the silyl group.     

An unusual decarboxylative benzannulation and biaryl formation during copper(I)-promoted halogen atom transfer radical cyclization of 2-allylaryl trichloroacetates

CuCl/bpy-promoted halogen atom transfer radical cyclization of 2-allylaryl trichloroacetates in refluxing benzene gave benzannulated chloroarenes and benzannulated symmetrical biaryls along with reductive dehalogenation products. The unusual decarboxylative benzannulation and biaryl formation might be explained by a further intramolecular radical addition on the benzene ring of the eight-membered lactone intermediate, initially formed through 8-endo-trig halogen atom transfer radical cyclization, followed by decarboxylation, radical dimerization and dehydrochlorination reactions.     

Efficient one-pot synthesis of anti-HIV and anti-tumour β-carbolines

Thermal electrocyclisation of the azahexatriene system has been used as a key step for the synthesis of anti-HIV and anti-tumour compounds, harman, derivatives of harman and 1-aryl-β-carbolines. A one-pot reaction sequence was used to furnish these compounds in good yield.