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A Synthesis of Densely Functionalized 2,3‐Dihydropyrans Using Ring‐Closing Metathesis and Base‐Induced Rearrangements of Dihydropyran Oxides
Author(s) -
Schmidt Bernd,
Wildemann Holger
Publication year - 2000
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200009)2000:18<3145::aid-ejoc3145>3.0.co;2-b
Subject(s) - dihydropyran , chemistry , steric effects , organic chemistry , ceric ammonium nitrate , ring closing metathesis , salt metathesis reaction , metathesis , catalysis , grafting , polymerization , polymer
The preparation of dihydropyran and dihydrofuran oxides and their rearrangement in the presence of lithium dialkylamides to functionalized 2,3‐dihydropyrans or 2,3‐dihydrofurans, respectively, is described. The regiochemical outcome of the reaction can be influenced by the relative configuration of the starting epoxides and the steric demand of the base. The 2,3‐dihydropyrans obtained were converted stereoselectively to difunctionalized 3,4‐dihydropyrans by the carbon‐Ferrier reaction, or to fused acetals by addition of dimedone, mediated by ceric ammonium nitrate. The stereochemical results are rationalized by mechanistic proposals.