Utilization of an oxonia-Cope rearrangement as a mechanistic probe for Prins cyclizations.
An oxonia-Cope rearrangement was used as an internal clock reaction to probe the mechanism of the Prins cyclization reaction and the subsequent nucleophilic capture of the resultant tetrahydropyranyl cation. The oxonia-Cope rearrangement was shown to occur rapidly under typical Prins cyclization conditions when the oxocarbenium ion resulting from the rearrangement is similar to or lower in energy than the starting oxocarbenium ion. Oxonia-Cope rearrangements can be disfavored by destabilizing the resultant oxocarbenium ion or by stabilizing an intermediate tetrahydropyranyl cation. Stereoselectivity in the nucleophilic capture was dramatically affected by the reactivity of the nucleophile and electrophile. More reactive partners combined rapidly to give axial-substituted Prins products through a least-motion pathway. High selectivity for the equatorial-substituted tetrahydropyran was observed for less reactive nucleophiles and electrophiles.
Department of Chemistry, University of California, Irvine, California 92697-2025, USA.
Ramesh
R
Jasti
Christopher D
CD
Anderson
Scott D
SD
Rychnovsky
D000085:Acetates / Q000737:chemistry*; D001965:Bromides / Q000737:chemistry; D003500:Cyclization; D004164:Diphosphonates / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D013237:Stereoisomerism
D000085:Acetates; D001965:Bromides; D004164:Diphosphonates; C118890:Oxonia Active; D006861:Hydrogen Peroxide