title: Synthesis of 3,4-dihydro-2H-pyrans by hetero-Diels-Alder reactions of functionalized alpha,beta-unsaturated carbonyl compounds with N-vinyl-2-oxazolidinone.
abstract: Cycloadditions of 3-aryl-2-benzoyl-2-propenenitriles and 3-phenylsulfonyl-3-buten-2-one to N-vinyl-2-oxazolidinone proceed regio- and diastereoselectively yielding cis and trans diastereoisomers of 4-aryl-3,4-dihydro-2-(2-oxo-3-oxazolidinyl)-2H-pyrans in 37-65% yield. Cycloadducts cis- were the major products. Reaction of 5-arylidene-1,3-dimethylbarbituric acids with dienophile afforded mixtures of 2H-pyrano[2,3-d]pyrimidine-2,4(3H)-diones trans and products resulted from an elimination of 2-oxazolidinone, in 50-52% yield. To confirm the experimental results, semiempirical AM1 and PM3 calculations of frontier orbital energies have been performed.
authors.affiliation: Department of Organic Chemistry, Jagiellonian University, Ingardena 3, Pl-30060 Kraków, Poland. palasz@chemia.uj.edu.pl
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Pałasz
mesh_terms: D003500:Cyclization; D009682:Magnetic Resonance Spectroscopy / Q000379:methods / Q000592:standards; D015394:Molecular Structure; D023303:Oxazolidinones / Q000737:chemistry*; D011714:Pyrans / Q000138:chemical synthesis*; D012015:Reference Standards; D013237:Stereoisomerism
chemical_list: C506711:N-vinyl-2-oxazolidinone; D023303:Oxazolidinones; D011714:Pyrans