Heteroleptic Complexes of Zirconium Acetylacetonates: Better Precursors for the Preparation of Zirconia. Structural Characterization of [(acac)2Zr{ONC(Me)py‐2}2]

The reactions of the heteroleptic zirconium diisopropoxide bis(acetylacetonate) in benzene solution with two equivalents of oximes, alkoxyalkanols, triphenylsilanol and trimethylsilyl acetate yield products with the formula [{MeC(O)CHC(O)Me}₂ZrL₂] with L = —ONC(Me)C₅H₄N‐2, —ONC(Me)C₄H₃O‐2, —OCH₂CH₂OR (R = Me, Et, Buⁿ; py = pyridine, fu = furan), —OSiPh₃ and —OSiMe₃. Most of these derivatives are solids, but the [(acac)₂Zr(OSiMe₃)₂] is a viscous oil. They could be purified either by recrystallization or by vacuum distillation; all of these are monomeric in boiling benzene. Their elemental analyses, molecular weight measurements and IR as well as NMR spectra were measured. The oximato complex [(acac)₂Zr{ONC(Me)py‐2}₂] has been shown by single crystal X‐ray crystallography to be monoclinic and mononuclear in the solid state, where zirconium has the coordination number 8; all the ligands are situated in cis‐ position and the oximato ligand binds via N and O in a dihapto (η²‐N, O) manner.     

A concise synthesis of novel naphtho[a]carbazoles and benzo[c]carbazoles

Starting from simple indole precursors the synthesis of naphtho[a]carbazoles and benzo[c]carbazoles is described. Key steps include the use of the Suzuki-Miyaura reaction to afford 2- or 3-aryl substituted indoles, as well as a potassium t-butoxide and light assisted aromatic ring-forming reaction.     

The Weierstrass-Jacobi transform

The Weierstrass-Jacobi transform of a function ?, defined by $$f \left( n \right) = \sum\limits_{m = 0}^\infty { h \left( {n, m; 1} \right) \phi \left( m \right) h_{\alpha ,\beta } \left( m \right)} $$ is considered. It is inverted by means of a suitable difference operator e^?∈_n. In terms of Jacobi difference operator ∈_n a theory analogous to that of hormonic functions is presented. A characterization of those functions which are Weierstrass-Jacobi transform of positive functions is given.     

Asymptotic expansions of the Mehler-Fock transform

Asymptotic expansions in the two limitsx → + ∞ andx → 0+ are obtained for the Mehler-Fock transform

The synthesis of angularly fused polyaromatic compounds by using a light-assisted, base-mediated cyclization reaction

The synthesis of substituted polyaromatic compounds that contain at least four benzene rings fused together in an angular fashion is described. Suzuki coupling of 1-bromo-3,4-dihydronaphthalene-2-carbaldehyde with a number of aromatic boronic acids affords products such as 1-(1,4-dimethoxy-3-methyl-2-naphthyl)-3,4-dihydronaphthalene-2-carbaldehyde. Exposure of these dihydronaphthalenes to potassium tert-butoxide and DMF at 80 degrees C yields polyaromatic compounds such as 9,14-dimethoxynaphtho[1,2-a]anthracene.     

The evolution of photochemotherapy with psoralens and UVA (PUVA): 2000 BC to 1992 AD.

The therapeutic uses of naturally occurring psoralens in modern-day medicine (8-methoxypsoralen (8-MOP), 5-methoxypsoralen (5-MOP), 4,5',8-trimethylpsoralen, and a few other synthetic psoralens) have evolved through five stages of development. (1) In the historical period (2000 BC to 1930 AD), the pigment-stimulating properties of naturally occurring plants containing psoralens were described anecdotally. (2) The second period (1930-1960) dealing with the chemistry of psoralens involved extraction, identification of their structure, synthesis, and the relationship between chemical structure and their photoreactivity and pigment-stimulating properties. The treatment of vitiligo with oral and topical 8-MOP became popular. (3) In the third period (1960-1974), we witnessed a new beginning and the growth of basic science studies and clinical investigations into various biological properties of psoralens including action spectrum studies, mutagenesis and carcinogenesis studies, in vitro and in vivo photoreactivity studies of various psoralens with DNA, RNA, proteins, and pharmacological and toxicological studies in vitiligo patients undergoing long-term therapy for repigmentation. (4) The fourth period (1974-1988) is recognized as the period of photochemotherapy and the development of the science of photomedicine which established the therapeutic effectiveness of psoralens in combination with newly developed UV irradiation systems that emitted high-intensity UVA radiation in the treatment of severe psoriasis, mycosis fungoides, and over 16 other skin diseases. The effectiveness of PUVA (psoralen + UVA) was confirmed by well controlled clinical trials in thousands of patients, both in the USA and in European countries. Combination therapy with oral retinoids and PUVA contributed to greater effectiveness and long-term safety of psoralen photochemotherapy. (5) In the fifth period (1989 and beyond), psoralens are now emerging as photochemoprotective agents against non-melanoma skin cancers and as immunologic modifiers in the management of certain patients with disorders of circulating T-cells using new techniques of photopheresis. In the final analysis, perhaps the application of pharmacological and therapeutic concepts and principles of using psoralens in combination with UVA has contributed to the development of a new science of photomedicine in which the interaction between basic scientists, photobiologists, and physicians has produced both basic and new clinical knowledge for the care and control of human suffering.     

Excess volumes of isomeric butanols with di-n-butyl ether

The excess volumes of four isomeric butanols with di-n-butyl ether were determined at 30°C. The isomeric effect was distinctly observed in the excess volume profiles. 1-Butanol and 2-methyl-l-propanol systems exhibited negative excess volumes throughout the concentration range. The 2-butanol system had positive excess volumes up to 0.9 mol fraction of alcohol after which it became negative, while the 2-methyl-2-propanol system exhibited positive excess volumes throughout the concentration range. NCL Communication No. 4678     

Vibrational Dynamics and Heat Capacity of Trans‐1,4‐Polyisoprene (α‐Form)

Vibrational dynamics of the α‐polymorphic form of trans‐1‐4‐polyisoprene is described using Higg's method and the Urey‐Bradley force field. Characteristic features of dispersion profiles such as repulsion and bunching are reported. A comparison with the β‐form is presented and possible reasons for variation in heat capacity are discussed.     

Highly efficient Pd‐PEPPSI‐IPr catalyst for N‐(4‐pyridazinyl)‐bridged bicyclic sulfonamides via Suzuki–Miyaura coupling reaction

A protocol for the Suzuki–Miyaura coupling of novel 2‐(6‐chloropyridazin‐3‐yl)‐5‐(aryl/heteroarylsulfonyl)‐2,5‐diazabicyclo[2.2.1]heptanes and heteroarylboronic acids to afford variety of coupled products was realized. Pd‐PEPPSI‐IPr catalyst was found to be a powerful and reusable catalyst under relatively mild reaction conditions.