Stereochemistry of the thermal isomerizations of (2S,3R-methoxymethyl-2,3-dideuterio-1-(dideuteriomethylene)cyclopropane

The (2S,3R) isomer of 2-methoxymethyl-2,3-dideuterio-1-(dideuteriomethylene)cyclopropane has been synthesized and heated at 198.8°: from the experimentally observed mol fractions of the eight isomers of 2,3,α,α,- and 2,3,3,α - tetradeuterio - 2 - methoxymethyl - 1 - methylenecyclopropane in the pyrolysis product mixture have been derived rate constants for seven distinct modes of isomerization. One-center thermal epimerizations at C(2) and C(3) and the C(2)C(3) two-center epimerization are of kinetic importance. Only two of four observable stereochemical modes for carbon [1,3] shifts are seen: there is inversion of stereochemistry at the migrating C atom, while the C(3)H trans to C(2)-CH₂OCH₃ in starting material becomes syn 4 : 1 C(α)-H in the [1,3] shift product. Stereomutation at C(2) does not occur along the reaction coordinate for [1,3] carbon shifts.     

Comparison of fuzzy sets on the same decision space

Some methods of making fuzzy decisions include a comparison of fuzzy sets on the same space. Methods have been published which suffer from lack of discrimination between alternatives and occasional conflict with intuitive choice. These methods are reviewed in this paper and then a new approach is described which overcomes their drawbacks. Methods of evaluating the parameter used in decision-making are given which can be varied to incorporate different utility functions.     

Heterogeneous reactions of sulfur dioxide with carbonaceous particles

The rate of adsorption of SO₂ on a prototype carbonaceous surface was measured at low pressure in a flow reactor. The measured rate indicates a maximum atmospheric loss of SO₂ by heterogeneous reaction of 1%/h for a particle density of 100 μg/m³. The capacity of carbon particles to adsorb SO₂ is limited at ～1 mg SO₂ g^?1 C. NO₂ has no effect on the rate of SO₂ adsorption or the saturation behavior.     

Approaches to the regiospecific synthesis of Anthracycline antibiotics

Synthetic approaches to anthracycline antibiotics were studied through the use of Claisen rearrangements on 1-methallyloxy-5-methoxyantraquinone (9) which required reducing conditions to proceed through a hydroquinone intermediate in situ. 1-(2′-Methylene-4′-pentenoxy)-5-methoxyanthraquinone (13) underwent a similar reductive rearrangement but also produced a spiro compound 16 as a result of an ene reaction between the phenol and side chain double bond. 1-Hydroxy-2-methally-5-methoxyanthraquinone (11) could not be oxidized to quinizarin 17. 1-Hydroxy-2-methally-5,9,10-trimethoxyanthracene (21) was oxidatively coupled to the dimer at C-2. Dimer 23 reacted with diazomethane to form a 1,3-dipolar adduct 24.     

The stereochemistry of cyclisation of n-t-butyldihydrocinnamamide to a β-lactam

Using a stereospecifically labelled precursor, the peroxide catalysed cyclisation of N-$\text{t}$-butyldihydrocinnamamide to the corresponding β-lactam was shown to proceed with complete loss of stereochemistry at the benzylic carbon atom.     

Crystal and molecular structure of diaquobis(1,1′-dimethyl-2,2′-diimidazolylsulfide)copper(II) methylsulfate, (C8H10N4S)2Cu(II)(OH2)2(CH3OS03)2

The crystal and molecular structure of the title complex has been determined. The space group isP2₁/n, witha=8.460(3),b=8.503(3),c=20.341 (8) Å,=98.41(3) andZ=2. The ligand molecules chelate the Cu^II such that the metal has a tetragonally distorted octahedral geometry; four N atoms occupy the equatorial plane and two H₂O molecules occupy the axial positions. The average Cu-N and Cu-O distances are 2.005(6) and 2.47(1) Å, respectively. The novel ligand, 1,1-dimethyl-2,2-diimidazolylsulfide was formedin situ from a methanolic solution of copper(II) sulfate pentahydrate and 1-methylimidazole-2-thiol. The measured spectral parameters (visible, EPR, and photoelectron spectroscopy) correlate well with the molecular structure.     

A novel oxidative rearrangement of 6-methoxypyran-2-ones

As part of our continuing studies of pyrone-containing natural products, a series 6-methoxypyran-2-ones were synthesized. These were found to react with molecular oxygen at 20 degrees C, and this novel reaction yielded a series of highly functionalized alpha,beta-butenolides. [reaction: see text]