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Intermolecular Hetero Diels‐Alder Reactions of Enamino Ketones with Highly Substituted Vinyl Ethers Effect of High Pressure on the Kinetics and Diastereoselectivity
Author(s) -
Buback Michael,
Kuchta Gabriele,
Niklaus Anja,
Henrich Marielouise,
Rothert Iris,
Tietze Lutz F.
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960714
Subject(s) - chemistry , kinetics , cycloaddition , dichloromethane , diastereomer , vinyl ether , ketone , isomerization , intermolecular force , ether , methyl vinyl ketone , photochemistry , yield (engineering) , diels–alder reaction , medicinal chemistry , organic chemistry , solvent , polymer , catalysis , molecule , physics , quantum mechanics , copolymer , materials science , metallurgy
The hetero Diels‐Alder reactions of enamino ketones 1 and 2 with the vinyl ethers 3–5a are studied in dichloromethane solution under high pressures up to 5 kbar. The kinetics is measured by on‐line FT‐IR spectroscopy to 3 kbar. The cycloaddition reactions of enamino ketones 1 and 2 with vinyl ethers 3 and 4 yield the diastereomeric dihydropyrans 7a–d and 8a–d , respectively, whereas in the cycloaddition of enamino ketone 1 to vinyl ether 5a the constitutional isomers 9 and 11 are formed. The unexpected reaction of 1 with 5a to give the spiro compound 9 is explained by isomerisation of 5a to 5b under the reaction conditions. The kinetics of the reactions is discussed in terms of both overall and individual rate coefficients, activation energies, and activation volumes