title: Racemization in Prins cyclization reactions.
abstract: Isotopic labeling experiments were performed to elucidate a new mechanism for racemization in Prins cyclization reactions. The loss in optical activity for these reactions was shown to occur by 2-oxonia-Cope rearrangements by way of a (Z)-oxocarbenium ion intermediate. Reaction conditions such as solvent, temperature, and the nucleophile employed played a critical role in whether an erosion in enantiomeric excess was observed. Additionally, certain structural features of Prins cyclization precursors were also shown to be important for preserving optical purity in these reactions.
authors.affiliation: Department of Chemistry, University of California-Irvine, 1102 Natural Sciences II, Irvine, CA 92697-2025, USA.
authors.forename: Ramesh
authors.initials: R
authors.lastname: Jasti
authors.forename: Scott D
authors.initials: SD
authors.lastname: Rychnovsky
mesh_terms: D000085:Acetates / Q000737:chemistry; D003500:Cyclization; D004164:Diphosphonates / Q000737:chemistry; D006838:Hydrocarbons / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D007553:Isotope Labeling; D009682:Magnetic Resonance Spectroscopy; D008698:Mesylates / Q000737:chemistry*; D008697:Methane / Q000031:analogs & derivatives / Q000737:chemistry; D008956:Models, Chemical; D009904:Optical Rotation; D011714:Pyrans / Q000138:chemical synthesis*; D012997:Solvents / Q000737:chemistry; D013237:Stereoisomerism; D013696:Temperature; D013816:Thermodynamics
chemical_list: D000085:Acetates; D004164:Diphosphonates; D006838:Hydrocarbons; D008698:Mesylates; C118890:Oxonia Active; D011714:Pyrans; D012997:Solvents; C030011:carbene; D006861:Hydrogen Peroxide; D008697:Methane