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The Hetero‐Diels–Alder Addition of Sulfur Dioxide: The Pseudo‐Chair Conformation of a 4,5‐Dialkylsultine
Author(s) -
Markovic Dean,
Roversi Elena,
Scoppelliti Rosario,
Vogel Pierre,
Meana Rubén,
Sordo José A.
Publication year - 2003
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200304932
Subject(s) - moiety , sulfur dioxide , chemistry , sulfur , anomer , quantum chemical , diene , diffraction , anomeric effect , crystallography , stereochemistry , computational chemistry , organic chemistry , molecule , physics , natural rubber , optics
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 °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 SO bonds.