title: The hetero-Diels-Alder addition of sulfur dioxide: the pseudo-chair conformation of a 4,5-dialkylsultine.
abstract: Even unsubstituted butadiene adds to sulfur dioxide in the hetero-Diels-Alder mode more rapidly than in the chelotropic mode. The sultine can be observed in equilibrium with the diene and the sulfur dioxide only at low temperature and in the presence of CF(3)COOH. Crystals of 4,5-dialkyl-sultine resulting from the SO(2) addition to 1,2-dimethylidenecyclohexane have been obtained at -100 degrees C and analyzed by X-ray diffraction. Quantum chemical calculations have shown that hyperconjugative interactions within the sulfinyl moiety are responsible for the anomeric effects observed in sultines that prefer pseudo-chair conformations with pseudo-axial Sdbond;O bonds.
authors.affiliation: Institute of Molecular and Biological Chemistry, Swiss Institute of Technology, BCH, 1015 Lausanne-Dorigny, Switzerland. pierre.vogel@epfl.ch
authors.forename: Dean
authors.initials: D
authors.lastname: Markovic
authors.forename: Elena
authors.initials: E
authors.lastname: Roversi
authors.forename: Rosario
authors.initials: R
authors.lastname: Scoppelliti
authors.forename: Pierre
authors.initials: P
authors.lastname: Vogel
authors.forename: Rubén
authors.initials: R
authors.lastname: Meana
authors.forename: José A
authors.initials: JA
authors.lastname: Sordo