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Intramolecular site selectivity in cation radical Diels–Alder cycloadditions of difunctional and trifunctional dienophiles
Author(s) -
Bauld Nathan L.,
Yang Jingkui
Publication year - 2000
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/1099-1395(200009)13:9<518::aid-poc288>3.0.co;2-9
Subject(s) - chemistry , moiety , cyclopentadiene , adduct , styrene , selectivity , diels–alder reaction , cycloaddition , intramolecular force , medicinal chemistry , polymer chemistry , organic chemistry , photochemistry , catalysis , copolymer , polymer
The cation radical Diels–Alder reactions of several difunctional and trifunctional dienophiles with 1,3‐cyclopentadiene, catalyzed by tris(4‐bromophenyl)aminium hexachloroantimonate, were determined. When both of the reactive sites are of the 4‐methoxystyrene type, reaction occurs smoothly at both styrene moieties to give the bis‐adducts. However, when one reactive moiety is of the styrene type and one is of the enol ether type, reaction occurs exclusively at the styrene moiety to give a mono‐adduct, even in the presence of a large excess of cyclopentadiene. When three potentially reactive moieties are included, two of them being of the styrene type and one of the 1,2‐diaryloxyethene type, the reaction is again specific for the styrene moieties, giving only the bis‐adduct. The high site selectivity observed in these reactions is especially noteworthy in view of the observation that monofunctional molecules containing all three of these moieties are found to be reactive toward Diels–Alder adduct formation under the same reaction conditions and that these adducts are relatively stable under the reaction conditions. Copyright © 2000 John Wiley & Sons, Ltd.