Stereochemistry of Seven-membered Heterocycles. XXXVI. Unprecedented Solvent Effect on Thermodynamical Parameters of Conformational Equilibrium of Model 1,2,3-Trithia-5,6-benzocycloheptene: Donor-Acceptor Interactions of Conformers with the Medium

Medium effect on the conformational equilibrium of a model seven-membered trisulfide represented in solutions by chair and boat conformations is studied by dynamic 1H NMR spectroscopy. Thermodynamic equilibrium parameters (ΔG0, ΔH0, and ΔS0) in nine solvents substantially differing in polar, acceptor, and donor properties, as well as in 5 M solution of lithium perchlorate in acetone are obtained. A pronounced compensation effect is revealed. The difference in the ΔH0 values in the studied media are as high as 6.6 kcal/mol, magnitudes of ΔS0 differ by up to 22 e.u. Analysis of the solvation energy components led us to conclusion that the observed effect depends on the donor-acceptor interaction of two conformers with the medium. Increasing acceptor properties of solvent result in the enthalpy stabilization of the boat form

Synthesis and stereochemistry of 1H,5H-naphtho[1,8-ef][1,3]dithiocine 2-oxides

3-Substituted 1H,5H-naphtho[1,8-ef][1,3]dithiocines (R = H, Me, Ph, t-Bu) were oxidized with m-chloroperoxybenzoic acid to the corresponding 2-oxides having trans configuration (R ≠ H). According to the 1H and 13C NMR data (including NOESY experiments), the disubstituted compounds at room temperature exist in a boat conformation with equatorial orientation of the substituent on C3 and oxygen atom on S 2. The compound with no substituent on C3 gives rise to a mixture of boat conformers with axial and equatorial sulfoxide oxygen atoms at a ratio of 83:17. © 2005 Pleiades Publishing, Inc

Stereochemistry of 1,3-dithia-5,6-benzocycloheptene-s-oxides

According to dynamic 13C NMR spectroscopy trans-2-R-(R=Ph, Me, Et, Pri)-5,6-benzocycloheptene-1-oxides at -60°C in CDCl 3 exist as an equilibrium mixture of the chair and boat forms with the substituents in the equatorial position. Unsubstituted (R=H) compound has in addition a boat form with an axial sulfinyl group, whereas for Bu t derivative conformational equilibrium is anancomerically shifted to the boat structure. X-ray study of trans-2-isopropyl-1,3-dithia-5,6- benzocycloheptene-1,3-dioxide displays a chair form with equatorial alkyl substituent and axial-equatorial SO-moieties. © 2003 Elsevier B.V. All rights reserved

Stereochemistry of Seven-membered Heterocycles. XXXVI. Unprecedented Solvent Effect on Thermodynamical Parameters of Conformational Equilibrium of Model 1,2,3-Trithia-5,6-benzocycloheptene: Donor-Acceptor Interactions of Conformers with the Medium

Medium effect on the conformational equilibrium of a model seven-membered trisulfide represented in solutions by chair and boat conformations is studied by dynamic 1H NMR spectroscopy. Thermodynamic equilibrium parameters (ΔG0, ΔH0, and ΔS0) in nine solvents substantially differing in polar, acceptor, and donor properties, as well as in 5 M solution of lithium perchlorate in acetone are obtained. A pronounced compensation effect is revealed. The difference in the ΔH0 values in the studied media are as high as 6.6 kcal/mol, magnitudes of ΔS0 differ by up to 22 e.u. Analysis of the solvation energy components led us to conclusion that the observed effect depends on the donor-acceptor interaction of two conformers with the medium. Increasing acceptor properties of solvent result in the enthalpy stabilization of the boat form

Stereochemistry of Seven-membered Heterocycles. XXXVI. Unprecedented Solvent Effect on Thermodynamical Parameters of Conformational Equilibrium of Model 1,2,3-Trithia-5,6-benzocycloheptene: Donor-Acceptor Interactions of Conformers with the Medium

Medium effect on the conformational equilibrium of a model seven-membered trisulfide represented in solutions by chair and boat conformations is studied by dynamic 1H NMR spectroscopy. Thermodynamic equilibrium parameters (ΔG0, ΔH0, and ΔS0) in nine solvents substantially differing in polar, acceptor, and donor properties, as well as in 5 M solution of lithium perchlorate in acetone are obtained. A pronounced compensation effect is revealed. The difference in the ΔH0 values in the studied media are as high as 6.6 kcal/mol, magnitudes of ΔS0 differ by up to 22 e.u. Analysis of the solvation energy components led us to conclusion that the observed effect depends on the donor-acceptor interaction of two conformers with the medium. Increasing acceptor properties of solvent result in the enthalpy stabilization of the boat form

Stereochemistry of Seven-membered Heterocycles. XXXVI. Unprecedented Solvent Effect on Thermodynamical Parameters of Conformational Equilibrium of Model 1,2,3-Trithia-5,6-benzocycloheptene: Donor-Acceptor Interactions of Conformers with the Medium

Medium effect on the conformational equilibrium of a model seven-membered trisulfide represented in solutions by chair and boat conformations is studied by dynamic 1H NMR spectroscopy. Thermodynamic equilibrium parameters (ΔG0, ΔH0, and ΔS0) in nine solvents substantially differing in polar, acceptor, and donor properties, as well as in 5 M solution of lithium perchlorate in acetone are obtained. A pronounced compensation effect is revealed. The difference in the ΔH0 values in the studied media are as high as 6.6 kcal/mol, magnitudes of ΔS0 differ by up to 22 e.u. Analysis of the solvation energy components led us to conclusion that the observed effect depends on the donor-acceptor interaction of two conformers with the medium. Increasing acceptor properties of solvent result in the enthalpy stabilization of the boat form

Synthesis and stereochemistry of 1H,5H-naphtho[1,8-ef][1,3]dithiocine 2-oxides

3-Substituted 1H,5H-naphtho[1,8-ef][1,3]dithiocines (R = H, Me, Ph, t-Bu) were oxidized with m-chloroperoxybenzoic acid to the corresponding 2-oxides having trans configuration (R ≠ H). According to the 1H and 13C NMR data (including NOESY experiments), the disubstituted compounds at room temperature exist in a boat conformation with equatorial orientation of the substituent on C3 and oxygen atom on S 2. The compound with no substituent on C3 gives rise to a mixture of boat conformers with axial and equatorial sulfoxide oxygen atoms at a ratio of 83:17. © 2005 Pleiades Publishing, Inc

Synthesis and stereochemistry of 1H,5H-naphtho[1,8-ef][1,3]dithiocine 2-oxides

3-Substituted 1H,5H-naphtho[1,8-ef][1,3]dithiocines (R = H, Me, Ph, t-Bu) were oxidized with m-chloroperoxybenzoic acid to the corresponding 2-oxides having trans configuration (R ≠ H). According to the 1H and 13C NMR data (including NOESY experiments), the disubstituted compounds at room temperature exist in a boat conformation with equatorial orientation of the substituent on C3 and oxygen atom on S 2. The compound with no substituent on C3 gives rise to a mixture of boat conformers with axial and equatorial sulfoxide oxygen atoms at a ratio of 83:17. © 2005 Pleiades Publishing, Inc

Synthesis and stereochemistry of 1H,5H-naphtho[1,8-ef][1,3]dithiocine 2-oxides

3-Substituted 1H,5H-naphtho[1,8-ef][1,3]dithiocines (R = H, Me, Ph, t-Bu) were oxidized with m-chloroperoxybenzoic acid to the corresponding 2-oxides having trans configuration (R ≠ H). According to the 1H and 13C NMR data (including NOESY experiments), the disubstituted compounds at room temperature exist in a boat conformation with equatorial orientation of the substituent on C3 and oxygen atom on S 2. The compound with no substituent on C3 gives rise to a mixture of boat conformers with axial and equatorial sulfoxide oxygen atoms at a ratio of 83:17. © 2005 Pleiades Publishing, Inc

Stereochemistry of 1,3-dithia-5,6-benzocycloheptene-s-oxides

According to dynamic 13C NMR spectroscopy trans-2-R-(R=Ph, Me, Et, Pri)-5,6-benzocycloheptene-1-oxides at -60°C in CDCl 3 exist as an equilibrium mixture of the chair and boat forms with the substituents in the equatorial position. Unsubstituted (R=H) compound has in addition a boat form with an axial sulfinyl group, whereas for Bu t derivative conformational equilibrium is anancomerically shifted to the boat structure. X-ray study of trans-2-isopropyl-1,3-dithia-5,6- benzocycloheptene-1,3-dioxide displays a chair form with equatorial alkyl substituent and axial-equatorial SO-moieties. © 2003 Elsevier B.V. All rights reserved