Lipophilic Functionalized Cobyrinic-Acid Derivatives. Part 1. Cobester α-monoacids (α,α,α,β,β,β-hexamethyl α-hydrogen Coα, Coβ-dicyanocobyrinates)

The four α,α,α, β,β,β,-hexamethyl α-hydrogen Coα, Coβ-dicyanocobyrinates 2b, d–f , with a free b-, d-, e-, and f-propionic-acid function, respectively, were prepared by partial hydrolysis of heptamethyl Coα, Coβ-dicyanocobyrinate (cobester; 1 ) in aqueous sulfuric acid. The cobester monoacids 2b, d–f were obtained as a ca. 1:1:1:1 mixture which was separated. The monoacids were purified by chromatography and isolated in crystalline form. The position of the free propionic-acid function was determined by an extensive analysis of 2b, d–f using 2D-NMR techniques; an analysis of the C,H-coupling network topology resulted in an alternative assignment strategy for cobyrinic-acid derivatives, based on pattern recognition. Additional information on the structure of the most polar of the four hexamethyl cobyrinates, of the b-isomer 2b , was also obtained in the solid state from a single-crystal X-ray analysis. Earlier structural assignments based on 1D-NMR spectra of the corresponding regioisomeric monoamides 3b, d–f (obtained from crystalline samples of the monoacids 2b, d–f ) were confirmed by the present investigations.     

Substituent effects of α,β-unsaturated aldehyde compounds in inverse electron demand Hetero-Diels–Alder reactions: A theoretical study

The present work describes the new theoretical study for behaviour estimation of some α,β-unsaturated aldehyde derivatives in inverse electron demand Hetero-Diels–Alder reactions. The theoretical scale has shown rationalization between electrophilic activation/deactivation effects and electron withdrawing (EW) and electron releasing (ER) substituents in these molecules. The electrophilicity values that evaluated with HF/6-31G* method shows a good linear relationship with the σ_p Hammett substituent constants. These results are in excellent agreement with respect to experimental results.     

Synthesis of α‐aminophosphonates from α‐hydroxyphosphonates; a theoretical study

Two types of reactions, namely the Pudovik reaction of benzaldehyde and acetophenone with diethyl phosphite as well as the substitution of the α‐hydroxyphosphonates so‐formed by primary amines to afford α‐aminophosphonates, were evaluated by quantum chemical calculations at the B3LYP/6‐31G(d,p) level. An unexpected neighboring group effect was found to enhance the substitution. A series of new α‐aminophosphonates was synthesized by the microwave‐assisted substitution of α‐hydroxyphosphonates by alkylamines.     

Cationic polymerization of α,β-disubstituted olefins. Part II. Cationic polymerization of propenyl N-butyl ether

The cationic polymerization of propenyl n-butyl ether (PBE) in methylene chloride with boron fluoride etherate at ?78°C. has been studied. The copolymerization of PBE with vinyl n-butyl ether (VBE) showed that both the isomers are more reactive than VBE, and their monomer reactivity ratios were found to be:     

Reactions of α,β‐Enones with Diazo Compounds. Part 4

In this study, (E)‐ and (Z)‐enones carrying only a phenyl substituent at their C(β) atom were treaced with dimethyl diazomalonate in the presence of (acetylacetonato)copper(II). According to the configuration of the starting enones, the products were dioxole or dihydrofuran derivatives, significant heterocycles in natural products.     

Kinetics of the reactions of cyclopropane derivatives. V. The gas-phase unimolecular reactions of 1 α-chloro-2α,3α-dimethylcyclopropane and 1α-chloro-2α,3β-dimethylcyclopropane

Thermolysis of the “all-cis” compound 1α-chloro-2α,3α-dimethylcyclopropane (A) at 550–607 K and 6–115 torr is a first-order homogeneous non-radical-chain process giving penta-1,3-diene (PD) and HCl as products. The Arrhenius parameters are log₁₀A(sec^?1) = 13.92 ± 0.08 and E = 199.6 ± 0.9 kJ/mol. The isomer with trans-methyl groups, 1α-chloro-2α,3β-dimethylcyclopropane (B) reacts by two parallel first-order processes giving as observed products trans-4-chloropent-2-ene (4CP) and PD + HCl, with log₁₀A(sec^?1) = 14.6 and 13.8, respectively, and E = 199.5 and 190.2 kJ/mol, respectively. The 4CP undergoes secondary decomposition to PD + HCl (as investigated previously). Comparison of the results for compounds (A) and (B) with those for other gas-phase and solution reactions leads to the conclusion that the gas-phase thermolyses proceed by rate-determining ring opening to form olefins which may decompose further by thermal or chemically activated reactions, and that the ring opening is a semiionic electrocyclic reaction in which alkyl groups in the 2,3-positions trans to the migrating chlorine semianion move apart, with appropriate consequences for the rate of reaction and the stereochemistry of the products.     

Fe(II)-Induced Fragmentation Reaction of γ-Hydroperoxy-α,β-enones. Part 1. Synthesis of 13(14→8)-abeo-Steroids

Some steroidal analogues embodying the hitherto unknown 13(14→8)-abeo skeleton have been synthesized by Fe(II)-induced rearrangement (tandem β-fission/reductive alkylation) of 14α-hydroperoxy-7-en-6-ones. The configurational assignment was made by thorough analysis of NMR spectra; the structure of one of the products was unambiguously assessed by X-ray single-crystal analysis.     

SCF-Xα-SW calculation on the molecule N2 using theoretical αta

The first calculation of a molecule, N₂, by the SCF -Xα-SW method using the theoretically derived parameter α_ta is reported.     

Biosynthesis of aristeromycln: Evidence for the intermediacy of a 4β-hydroxymethyl-1α, 2α, 3α-trihydroxycyclopentanetriol.

Evidence for the intermediacy of a 4β-hydroxymethyl-1α, 2α, 3α-trihydroxycyclopentanetdol (5 or6) in the biosynthesis of the nucleoside antibiotic aristeromycin (1) has been obtained by administration of doubly-labeled forms of D-glucose to the fermentation broth ofStreptomyces citricolor followed by trapping of the tetrol5 using isotope dilution methods.     

Reaction of Cα,O-dilithiooximes with functionalized carbonyl compounds. Part 2 . Reaction with α-chloroketones and α,β-unsaturated aldehydes and ketones

The reaction of Cα,O-Dilithiooximes 2 and α-chloroketones afforded 5-(hydroxymethyl)-Δ²-soxazolines 4 . α,β-Unsaturated aldehydes and ketones reacted with 2 to give the corresponding acyclic 1,2-addition products 5 . The latter were cyclized with phosphorus pentoxide to 5-vinyl-Δ²-isoxazolines 6 .     

α,β-Epoxyketon → Alkinon-Fragmentierung II: Pyrolytischer Zerfall der Hydrazone aus α,β-Epoxyketonen und N-Amino-aziridinen. Über synthetische Methoden, 4. Mitteilung

Numerous examples illustrate the course of the thermolysis of hydrazones derived from α,β-epoxyketones and 2-phenyl- or trans-2,3-diphenyl-1-amino-aziridines. This process constitutes a preparatively useful method for the fragmentation of α,β-epoxyketones to acetylenic carbonyl compounds including acetylenic aldehydes. Monohydrazones from phenylglyoxal and substituted N-amino-aziridines decompose smoothly and stereospecifically to the corresponding olefins and diazoacetophenone; such a process might also be useful for the preparation of other α-diazocarbonyl compounds.