Stereochemistry of Seven-Membered Heterocycles: XLI. Stereoselective Synthesis of 3-R-1,5-Dihydro-2,4-benzothiepine 2-Oxides

The oxidation of 3-R-1,5-dihydro-2,4-benzothiepines with m-chloroperbenzoic acid occurs in a highly diastereoselective fashion. The resulting trans-sulfoxides at -60°C in CDCl3 exist as an equilibrium mixture of the chair and boat forms with the substituents in the equatorial position. The fraction of the boat conformation increases in the series R = Ph, Me, t-Bu.     

Synthesis and Stereochemistry of 1<Emphasis Type="Italic">H</Emphasis>,5<Emphasis Type="Italic">H</Emphasis>-Naphtho[1,8-<Emphasis Type="Italic">ef</Emphasis>][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 S². 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.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1109–1112.Original Russian Text Copyright © 2005 by Kikilo, Khairutdinov, Shtyrlin, Klochkov, Klimovitskii.