title: Organocatalysis in synthesis: L-proline as an enantioselective catalyst in the synthesis of pyrans and thiopyrans.
abstract: The multicomponent reaction (MCR) of aromatic aldehydes 1 and malononitrile (2) with active methylenes 5a-h in the presence of L-proline produced pyrans and thiopyrans 6a-h stereospecifically and in good yields. Moreover a novel MCR of ethyl propiolate (8) with 1 and 2 in the presence of L-proline to afford (R)-polysubstituted pyran is also reported. X-ray structures, e.e. and optical activity of the synthesized compounds indicated that L-proline as a catalyst is responsible for the observed enantioselectivity in the studied reactions.
authors.affiliation: Women Students-Medical Studies & Sciences Sections, Chemistry Department, College of Science, King Saud University, Riyadh, KSA, P.O. Box 22452, Riyadh 11495, Saudi Arabia. elnagdinoha@yahoo.com
authors.forename: Noha M Hilmy
authors.initials: NM
authors.lastname: Elnagdi
authors.forename: Noura Saad
authors.initials: NS
authors.lastname: Al-Hokbany
mesh_terms: D002384:Catalysis; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011392:Proline / Q000737:chemistry*; D011714:Pyrans / Q000138:chemical synthesis*; D013438:Sulfhydryl Compounds / Q000138:chemical synthesis*
chemical_list: D011714:Pyrans; D013438:Sulfhydryl Compounds; C522033:thiopyran; D011392:Proline