A stereoselective and atom-efficient approach to multifunctionalized five- and six-membered rings via a novel michael-initiated intramolecular Diels-Alder furan reaction.
[reaction: see text] 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 beta-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.
Namboothiri
Irishi N N
IN
Department of Chemistry and National Single-Crystal X-ray Diffraction Facility, Indian Institute of Technology, Bombay, Mumbai 400 076, India. irishi@iitb.ac.in
Ganesh
Madhu
M
Mobin
Shaikh M
SM
Cojocaru
Miriam
M
D006576:Heterocyclic Compounds, 4 or More Rings / Q000138:chemical synthesis*; D008968:Molecular Conformation; D013237:Stereoisomerism
D006576:Heterocyclic Compounds, 4 or More Rings