Oxetane Ring Research Articles

Structures of some taxane diterpenoids, baccatins-III, -IV, -VI, and -VII and 1-dehydroxybaccatin-IV, possessing an oxetan ring

Baccatin-III (3), IV (5), -VI (7), and -VII (8) and the 1-dehydroxy derivative of baccatin-IV are taxane derivatives with an oxetan ring.

INDO- and CNDO-Approximated Molecular Orbital Calculations on the Spin-Spin Coupling Constants in Some 2-Substituted Oxetanes

Spin-spin coupling constants between the methine proton in the oxetane ring and the phenyl protons and carbon nuclei have been calculated in different conformations in the INDO approximation for 2-phenyloxetane and 2-(4-fluorophenyl) oxetane, and in the CNDO approximation for 2-(2- chlorophenyl) oxetane and 2-(3-chlorophenyl) oxetane. In each case the finite perturbation method has been used. In the case of 2-(2-chlorophenyl) oxetane a fairly high energy barrier for the rotation around the C-C bond between the rings is obtained, while in the other three cases the barrier is much lower. The calculations predict an equilibrium conformation in which the oxygen atom lies almost in the plane of the aromatic ring. The calculated dipole moments of 2-(2-chlorophenyl) oxetane and 2-(3-chlorophenyl) oxetane vary significantly with conformation.

Hypoiodite reaction of N-acetyljervine: The formations of oxepane and oxetane rings by hetero atom insertion from alkoxyl radical

Hypoiodite reaction of N-acetyljervine: The formations of oxepane and oxetane rings by hetero atom insertion from alkoxyl radical

Studies on the PMR Spectra of Oxetanes . V. 2-(3,4-Dichlorophenyl)oxetane and 2-(2,4-Dichlorophenyl)oxetane

The 60 MHz proton magnetic resonance spectra of 2-(3,4-dichlorophenyl)oxetane and 2-(2,4-dichlorophenyl)oxetane in 10 mole per cent CCl4 solution have been analyzed using the sub-spectral method. The proton chemical shifts and the proton-proton couplings have been determined. Some aspects concerning the effects of the 3- and 2-chlorines in the phenyl ring on the magnetic parameters have been put foward. The proton-proton couplings 4J0 and 5Jm from the benzyl proton to the ortho and meta protons in-the phenyl ring, respectively, were found to be opposite in sign. Comparing the absolute values of these couplings, it was concluded that the rotation around the Ph-C bond between the phenyl and oxetane rings is more hindered in 2-(2,4-dichlorophenyl)oxetane than in 2-(3,4-dichlorophenyl)oxetane.

Photochemical addition of acetone to D-glucal triacetate and subsequent oxetane ring cleavage

Photochemical addition of acetone to D-glucal triacetate and subsequent oxetane ring cleavage

The Acid-catalyzed Reaction of Isocyanide with Oxetane

Abstract The reaction of isocyanide with oxetane in the presence of BF3·OEt2 was studied; in this reaction a 1:1 cyclic adduct, 2-iminotetrahydrofuran, was formed. From 2-methyloxetane, 2-imino-5-methyltetrahydrofuran was exclusively formed. These findings suggest an SN2 mechanism for the cleavage of the oxetane ring. Oxetanes with electron-withdrawing substituents gave γ-alkoxybutyronitrile as the main product, along with 2-iminotetrahydrofuran. A reaction scheme involving an imidoyl cation was proposed to explain the formation of cyclic and linear products.

Studies on the PMR Spectra of Oxetanes

Abstract The 60 MHz PMR spectra of 2 -(4-iodophenyl) oxetane, 2-(4-bromophenyl) oxetane, 2-(4-fluoro-phenyl) oxetane, and 2-(4-chlorophenyl) oxetane have been analysed for the oxetane ring protons and the phenyl protons. In the three first mentioned compounds the spectra show a coupling of 0.46 - 0.63 Hz between the benzyl proton and the phenyl protons in ortho position relative to the oxetane ring, the other proton-proton couplings between the oxetane and phenyl parts being zero in the error limits. In the oxetane part, the halogen substituent in the para position of the phenyl ring mainly affects the chemical shifts of the protons with a slight effect on the proton-proton couplings. The ortho and meta couplings of the phenyl protons increase and the para coupling decreases with growing electronegativity of the substituent, in the order iodine, bromine, fluorine. The phenyl protons in 2-(4-chlorophenyl) oxetane produce a sharp singlet, which shows that they are chemically equivalent. This proves that chlorine and the oxetane group affect the shieldings of the phenyl protons similarly, which is supported by comparing the chemical shift differences in 2-(4-halophenyl) oxetanes to the ones in para-dihalo-substituted benzenes.

Studies on the PMR Spectra of Oxetanes. III. 2-Methyloxetane

Abstract The 60 MHz PMR sub-spectral analysis of 2-methyloxetane (A3BCDEF spin system) has been carried out approximating some weak couplings to zero. The proton chemical shifts and the proton-proton couplings are reported. Also the proton chemical shifts of symmetrically substituted 2,2-di-methyloxetane and 3,3-dimethyloxetane have been investigated. The anisotropy and inductive effects of the methyl groups, together with the evidently nonplanar structure of the oxetane ring in 2-methyloxetane, affect the spectral parameters of the protons under inspection

Studies on the PMR Spectra of Oxetanes

Abstract The oxetane parts of 2-(4-methylphenyl) oxetane, 2-(2,4-dimethylphenyl)oxetane and 2-(2,4,6-tri-methylphenyl) oxetane have been analysed as the ABCDE spin systems from the 60 MHz PMR spectra. The chemical shifts and the proton-proton couplings of the protons in the oxetane rings have been solved through iterative calculations. The possible phenomena which may affect the chemical shifts and couplings have been investigated. One of the most dominating factor seems to be the non-planarity of the oxetane ring. The ring current effects of the 2-substituents and the field effects of the methyl groups shift the resonances of the oxetane ring protons.

Crystallographic structure determination of the diterpenoid baccatin-V, a naturally occurring oxetan with a taxane skeleton

Baccatin-V, C31H38O11, a new diterpenoid from Taxus baccata L. has been shown by X-ray analysis to contain an oxetan ring and to be 5β,20-epoxy-1β,2α,4α,7α,10β,13α-hexahydroxytax-11-en-9-one 4α,10β-diacetate 2α-benzoate (I).

Synthesis of 3-oxabicyclo[3,1,1]heptanes by rearrangement of 3-oxaspiro[3,3]heptanes

Reaction of 3,3-bis(chloromethyl)oxetan with tris(ethoxycarbonyl)methane yields diethyl carbonate and diethyl-2-oxaspiro[3,3]heptane-6,6-dicarboxylate (II). Reduction of this diester yields the corresponding diol (III), but longer reaction time leads to cleavage of the oxetan ring. When heated, or upon attempted acid hydrolysis, this diol (III) rearranges to the 3-oxabicyclo[3,1,1]heptane derivative (VI; X = OH) and similar rearrangement occurs with acetic anhydride or thionyl chloride. Acid hydrolysis converts the diester (II) into 3,3-bis(hydroxymethy)cyclobutane-1,1-dicarboxylic acid which rapidly cyclises to its monolactone.

Photo-addition of alkenes and alkynes to 3-carene-2,5-dione

A number of photo-addition reactions have been carried out on the enedione system of 3-carene-2,5-dione by direct irradiation in the presence of a variety of alkenes and alkynes. Addition to the carbon–carbon double bond is by far the major pathway, and indeed in only one case is there evidence for formation of an oxetane ring. In the case of the unsymmetrical addends, the direction of addition which produces the cyclobutane or cyclobutene appears to be in accord with previous experiments on simpler systems.

2,6,8‐trioxaspiro(3,5)nonane preparation, polymerization and polymer propertiess

AbstractIn this paper are described the preparation of 2,6,8‐trioxaspiro(3,5)nonane (I) which has two different and polymerizable rings in one molecule, its cationic polymerization, and some properties of the polymer. I was Prepared by the action sodium hydroxide on 5‐bromomethyl‐5‐hydroxymethyl‐1,3‐dioxan, which was obtained from pentaerythritol monobromide and paraformaldehyde in the presence of hydrochloric acid. The polymerization of I was carried out in methylene chloride by using BF3. (C2H5)2O as a catalyst, giving highly crystalline polymers (m.p., 220‐225°C.). The results of IR‐analysis of the polymer, together with its solubility and melting properties, indicated that the polymerization occurred primarily through ring opening of the oxetane ring in the monomer without appreciable extent of cross‐linking by opening of the 1,3‐dioxan ring. The thermal stability of the polymer was examined both in air and nitrogene atmosphere. 5‐Methylene‐1,3‐dioxan besides formaldehyde was detected in the pyrolysis products, the formation of which was reasonably explainable by the cleavage of the main chain of the polymer through the so‐called β‐scission mechanism.

3,3-Disubstituted oxetanes : 3,3-Bis(nitromethyl)oxetane and the ultraviolet spectra of its nitronate anions

3,3-Bis(nitromethyl)oxetane (II) has been prepared by the Victor Meyer reaction from 3,3-bis(iodomethyl)oxetane. The UV spectra of its mono and bisnitronate anions and those of other α,ω-dinitroalkanes formed in 85% ethanolic NaOHaq have been determined and are discussed. The rather high value of the absorption maximum 257 mμ) observed for the bisnitronate anion of II is attributed to the combined electron withdrawing effects of the oxetane ring and the β-carbonitronate group. The results are compared with other data dealing with the effect of small rings on electronic spectra.

The structure of trimethylherqueinone B

By a combination of methods of chemical degradation and NMR spectroscopy, the structure of one of the trimethyl ethers of herqueinone has been assigned formula VI. The novel chemistry of this structure and certain of its degradation products includes facile opening of the oxetane ring with alkali, and cleavage of isopropyl alcohol from an 8-isobutyryl-1-naphthoic acid by alcoholic sodium hydroxide in presence of air (no reaction in absence of air). Certain of the properties of herqueinone are rather unexpected on the basis of the structure (VIII) which is indicated by the assigned structure for trimethylherqueinone B. Similar considerations apply to the structure (VII) which has been assigned by Barton et al. for the related pigment, atrovenetin.