Seven-membered acetals based on cis-2,3-Dichloro-2-butene-1,4-diol

cis-2,3-Dichloro-2-butene-1,4-diol was obtained by reduction of dichloromaleic anhydride with lithium aluminum hydride. Condensation of the diol with carbonyl compounds leads to seven-membered unsaturated acetals, viz., 5,6-dichloro-1,3-dioxa-5-cycloheptenes. © 1980 Plenum Publishing Corporation

Stereochemistry of seven-membered heterocycles Communication 12. Flexible form of tetrachlorophthalylformal and dipole moment of COCOC fragment in γ1 conformation

1. According to IR and13C NMR spectroscopic data, tetrachlorophthalylformal exists in the flexible form. 2. By the use of tetrachlorophthalyl sulfite as a model compound, the relative conformational energy of the tetrachloro-o-xylylene fragment has been determined to be -0.70±0.15 kcal/mole. 3. The group DM of the COCOC fragment in the gg1 conformation has been determined experimentally, and its components have been analyzed. © 1984 Plenum Publishing Corporation

Conformations of some 1,5-dioxaspiro[5.5]undecanes

1. A conformational equilibrium of the chair-like forms, which is shifted toward the conformers with an axial C-Hal bond, is characteristic for α-halocyclohexane trimethylene ketals. 2. The rotamer equilibrium due to the rotation about the exocyclic C-C bond, which is anancomerically shifted toward the t forms, is characteristic for the 2-chloromethyl(bromo-methyl)-1,3-dioxanes. © 1980 Plenum Publishing Corporation

New data on the raman spectra of 1,3-bioxepane. Observation of a three-component equilibrium

A conformational equilibrium between three forms was detected in 1,3-dioxepane by Raman spectroscopy of the crystal, the liquid, and solutions with various polarities. The fraction of the predominant TC1 form in benzene solution is 0.9. © 1988 Plenum Publishing Corporation

Stereochemistry of seven-membered heterocycles 5. The conformation of 1.3-dioxacyclohept-5-enes

1. According, to the results of dipole moment and IR and Raman spectroscopy methods, the butenediol acetal's (I)-(IX) are characterized by a conformational equilibrium of the chair and twist forms determined by the influence of various factors. 2. In the determination of the conformational equilibrium of the 2-alkyl-substituted acetals the influence of the "alkyl" dipole must be taken into account. © 1981 Plenum Publishing Corporation

Stereochemistry of seven-membered heterocycles 11. Isoenergy chair-twist conformation equilibrium in phthalylformal and its 2-phenyl derivative

By means of dynamic13C NMR, spectra have been obtained for the "frozen" chair and twist conformers of phthalylformal and its 2-phenyl derivative. The γ-effects of the phenyl substituent have been analyzed for both conformational species. 2. The introduction of a phenyl group into position 2 of phthalylformal is not reflected in the magnitude of the conformational free energy. © 1983 Plenum Publishing Corporation

Stereochemistry of seven-membered heterocycles. 3. Conformation of 5,6-dichloro-1,3-dioxacyclopent-5-enes and the planar-fragment effect

1. It is shown by dipole-moment measurements and IR and PMR spectroscopy that 2-R-5,6-dichloro-1, 3-dioxacyclohept-5-enes (R=C6H5, p-ClC6H4, p-NO2C6H4 and the corresponding cyclohexanone ketal exist in the flexible form; the 2-t-butyl analog exists in a chair-e-twist equilibrium depending on the polarity of the medium. 2. It is shown that a conformational planar-fragment effect occurs as a result of shielding of the C-Cl and C-H bonds in the chair form. © 1981 Plenum Publishing Corporation

Stereochemistry of seven-membered heterocycles. 4. Dipole moments and conformations of seven-membered ketals of α-halocyclohexanones

1. The conformational equilibrium in seven-membered 2-chloro(bromo)cyclohexanone ketals derived from 2-butenediol and its 2,3-dichloro and benzo analogs is ananchomerically shifted in favor of the axial form. 2. A graphical method is proposed for processing the dipole-moment data for this series of compounds. © 1981 Plenum Publishing Corporation

Seven-membered acetals based on cis-2,3-Dichloro-2-butene-1,4-diol

cis-2,3-Dichloro-2-butene-1,4-diol was obtained by reduction of dichloromaleic anhydride with lithium aluminum hydride. Condensation of the diol with carbonyl compounds leads to seven-membered unsaturated acetals, viz., 5,6-dichloro-1,3-dioxa-5-cycloheptenes. © 1980 Plenum Publishing Corporation

Stereochemistry of seven-membered heterocycles Communication 12. Flexible form of tetrachlorophthalylformal and dipole moment of COCOC fragment in γ1 conformation

1. According to IR and13C NMR spectroscopic data, tetrachlorophthalylformal exists in the flexible form. 2. By the use of tetrachlorophthalyl sulfite as a model compound, the relative conformational energy of the tetrachloro-o-xylylene fragment has been determined to be -0.70±0.15 kcal/mole. 3. The group DM of the COCOC fragment in the gg1 conformation has been determined experimentally, and its components have been analyzed. © 1984 Plenum Publishing Corporation