Conformational analysis of spiro-bis-dithiepins: a peculiar case of axial chirality.
Spiro-bis-dithiepins are synthesized via dehydrative ring expansion in alpha-hydroxyalkyl spiro-bis-dithianes. Atypical of spiranes possessing axial chirality, the two most stable conformers of substituted spiro-bis-dithiepin have virtually colinear double bonds; i.e., each enantiomer exists in a form of two energy degenerate syn and anti conformations. Because of the high polarizability of the vinyl sulfide moiety, spiro-bis-dithiepins bearing electron-withdrawing substituents offer access to two-state systems possessing large dipole moments, which can be modulated by conformational events. [structure: see text]
Wade
Edmir O
EO
Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, USA.
Valiulin
Roman A
RA
Ruybal
Leslie A
LA
Kutateladze
Andrei G
AG