E. Juaristi, S. Antúnez
1992
Citations
0
Influential Citations
22
Citations
Journal
Tetrahedron
Abstract
Abstract The positions of equilibrium, established by acid catalysis, between diastereomeric cis - and trans -5-methoxy- ( 2 ), 5-methanesulfonyloxy- ( 3 ), 5- p -(methylphenyl)sulfonyloxy- ( 4 ), and 5-( p -nitrophenyl)sulfonyloxy-2-phenyl-1,3-dioxanes ( 5 ) are reported. Quantitation of the O-C-C-O attractive gauche effects in these compounds revealed substantial gauche effects in 3 – 5 ; i.e., when the substituent at C(5) is tosylate, nosylate, and mesylate. No significant attractive gauche effect was observed for the 5-methoxy derivative. Good correlations between the magnitude of the attractive gauche effect and the positive character of the antiperiplanar hydrogens (H-4,6ax) in the cis diastereomers, as well as between the nucleofugicity of the 5-substituents and the energies for the unoccupied orbitals of lowest energy ( E LUMO ) in the corresponding dioxanes, appear to support a hyperconjugative interpretation of the attractive gauche effect.