摘要:
The intramolecular [4 + 2] cycloaddition of 1-thia-3-aza dienes is described. Substituted N-(trimethylsilyl)imines 2 derived from aromatic and heteroaromatic aldehydes 1 react with isothiocyanates to form heterodienes 3, which, although not isolated, undergo intramolecular cycloaddition at 90-degrees-C to yield heteropolycyclic compounds 5 and 7. The process was found to be regioselective and stereospecific; the stereochemistry of the cycloadducts arises from an exo transition state.