A Stereoselective and Atom-Efficient Approach to Multifunctionalized Five- and Six-Membered Rings via a Novel Michael-Initiated Intramolecular Diels−Alder Furan Reaction

A variety of key precursors to the intramolecular Diels−Alder reaction of furan diene (IMDAF)
have been prepared via a very facile 1,4-addition of O-, S-, N-, and C-centered nucleophiles possessing
unsaturated tether to β-furyl nitroethylene. Subsequent IMDAF reaction of the 1,4-adducts, carried
out under thermal conditions, provided five- and six-membered carbocycles and heterocycles fused
to an easily cleavable oxabicycloheptene moiety. The structure and stereochemistry of the
cycloadducts were determined by 2D-NMR experiments and further confirmed by X-ray crystallography. The salient features of the strategy include high degree of stereoselectivity (>80:20) in
the cycloaddition, atom and step economy, and generation of multiple chiral centers and
functionalities. The feasibility of the cleavage of the oxa bridge in the cycloadducts to afford novel
multifunctional molecules has also been demonstrated.