Stereochemistry of cyclic ether formation—II : Intramolecular cyclisation of secondary aliphatic alcohols to tetrahydrofuran-type ethers

The mechanism and stereochemistry of δ-C atom functionalisation in the reactions of secondary straight-chain aliphatic alcohols with lead tetraacetate, ceric ammonium nitrate, and heavy metal (Pb⁴⁺, Hg²⁺, Ag⁺) salts (AcO)^?1, O^2?, CO₃^2?-halogen (I₂, Br₂, Cl₂) combinations are discussed. By demonstrating the intermediacy of 5-bromo-2-hexanol, it was confirmed that the dark silver oxidebromine induced cyclisation of 2-hexanol (and alcohols in general) involves (as the other hypohalite reactions) intramolecular 1,5-hydrogen abstraction by alkoxy radicals and formation of δ-bromohydrins. A novel and simple procedure for obtaining tetrahydrofurans from alcohols by way of the hypochlorite reaction, using silver or mercuric salts and chlorine, is described.     

Resolution enhancement of a.c. polarographic peaks by deconvolution using the fast fourier transform

A method for resolution enhancement of a.c. polarograms (voltammograms) is presented. The method is based on deconvolution using fast Fourier transforms. Overlapped a.c. polarograms are mathematically narrowed and sharpened, retaining the peak position and linear proportionality of the sharpened peak height with concentration. The advantages and limitations of the method are demonstrated on simulated and experimental a.c. polarograms. The same approach is applicable to related techniques such as. differential pulse and square-wave polarography.     

Semiempirical studies of core electron binding energy shifts: Part 5. SCC—MO investigation of keto—enol tautomerism in some 1,3-diketones and related anhydrides

The keto—enol tautomerism in malonaldehyde and some related 1,3-diketones is thoroughly discussed by the calculation of inner-core binding energies. The semiempirical wave-functions were obtained by the self-consistent charge (SCC—MO) molecular orbital procedure. The calculated O(1s) binding energies are generally in good agreement with available experimental data. The discrepancy found for the alcohol-type oxygen in acetylacetone is so large that it strongly indicates an error in experimental assignment. The calculations also provide conclusive evidence that enol-forms possess asymmetric hydrogen-bonded protons.     

High-resolution IR spectrum of fluoroform: a close resonance

A very close triple resonance is observed in the Q-branch region of the C-H stretching fundamental transition in CF₃H. The vibrational perturbations are analysed in terms of the rotational structure and of the vibrational zero-order spectrum of totally symmetric states. The relationship to time-dependent intramolecular processes is discussed.     

Solution properties of poly(dialkyl-cyclohexyl) itaconates

Di(methyl-), di(ethyl-) and di(propylcyclohexyl) esters of itaconic acid were polymerized radically in bulk. The products were characterized in solution, then fractionated and the limiting viscosity number/molecular weight relations established for toluene at 25°. From extrapolations to θ-conditions, a set of σ-values from 2.75 to about 2.90 was obtained and compared with published results for poly(dicyclohexyl itaconate) [1], the first member of this polymer homologous series. The non-uniform change of unperturbed dimensions and other thermodynamic parameters are discussed in terms of chemical composition and constitution of the monomer residues.     

Circular dichroism of some cyclopropane ring containing 1,3-cyclo-5,10-seco-steroidal ketones

Circular dichroism of the rearranged keto steroids 3 and 4, containing a condensed three and nine-membered ring system, shows that the conformation of the nine-membered ring is the same in solution as in the crystal; reduction of the kto group does not change this situation. CD also indicates that epimerization at C(5) in the pair $\text{7}\text{8}$ and the pair $\text{11}\text{12}$ leaves the cyclononanone ring conformation unchanged.     

Synthesis,structure and reactions of seco-steroids containing a medium-sized ring—IX : Reactions of Δ1(10)-unsaturated 5-oxo-5,10-seco-steroids with hydroxylamine and n-methylhydroxylamine

When treated with hydroxylamine or N-methylhydroxylamine, in the presence of proton donor catalysts, trans-Δ¹⁽¹⁰⁾-unsaturated 5-oxo-5,10-seco-steroids, such as 3 (but not the corresponding diastereomeric cis-compounds), are converted stereospecifically and in good yield to isoxazolidine derivatives (e.g. 4 and 13), resulting from transannular 1,3-dipolar addition of the intermediately formed oximes and nitrones to the trans-double bond in the cyclodecene ring moiety of the seco-steroid system. Reactions are described and physical evidence is presented which establish the constitution and configuration of the isoxazolidine-containing cycloaddition products, and the mechanistic and steric course of this transannular ring closure process is discussed.     

Synthesis and solution properties of poly(diphenyl itaconate)

Solid diphenyl itaconate monomer was obtained by esterification in the presence of diphosphorus pentoxide and polymerized in bulk with AIBN as initiator. The non-film forming polymer powder was characterized by fractionation, viscosity measurements, light scattering and other techniques. The relation [n] = 3·6 × 10^?3$\text{M}$^0·70_w, obtained for toluene at 25° was extrapolated to θ-conditions by various procedures: the σ-value of 2·60 for unperturbed dimensions indicates a less pronounced influence of phenyl compared with other C₆ hydrocarbon substitutes.     

A convenient synthesis of 1α- and 1β-hydroxycholesterol

An efficient procedure for the preparation of 1α-hydroxycholesterol 3-acetate 4 is described, which starts from cholesterol and involves as key steps transannular cyclization of the ten-membered ring ontaining (E)-3β-acetoxy-5,10-seco-1(10)-cholesten-5-one 1 to the oxetane derivative 1α,5-epoxy-5α-cholestan-3β-ol acetate 3, and opening of the four-membered ether ring in the latter compound. 1β-Hydroxycholesterol diacetate 9 was obtained by oxidation of 4 to the 1-oxo derivative 8, followed by metal hydride reduction and acetylation.