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Electrocyclic Ring Opening Reactions of Ethylene Oxides
Author(s) -
Huisgen Rolf
Publication year - 1977
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.197705721
Subject(s) - conrotatory and disrotatory , ring (chemistry) , ethylene , chemistry , ethylene oxide , photochemistry , electrocyclic reaction , kinetic energy , computational chemistry , organic chemistry , physics , quantum mechanics , catalysis , polymer , copolymer
Substituents capable of stabilizing negative charge endow ethylene oxides with the ability to undergo electrocyclic ring opening at the CC bond; heating or irradiation generates small equilibrium concentrations of carbonyl ylides which can engage in 1,3‐dipolar cycloadditions. Apart from the normal conrotatory mode of ring opening, predicted by the Woodward‐Hoffmann rules, the disrotatory process, forbidden by orbital symmetry, also appears to occur in the case of α‐cyano‐ cis ‐stilbene oxide. Kinetic studies on α‐cyano‐ trans ‐and ‐ cis ‐stilbene oxide permit construction of the energy profile for electrocyclic ring opening to give the stereoisomeric carbonyl ylides and for their recyclization and rotation.