Diels-Alder Reactions of 2-Oxazolidinone Dienes in Polar Solvents Using Catalysis or Non-conventional Energy Sources (original) (raw)

2004, Monatshefte f�r Chemie - Chemical Monthly

The (Z)-N-substituted 4-methylene-5-propylidene-2-oxazolidinone dienes were prepared by a one-step synthesis, starting from 2,3-hexanedione and isocyanates. Diels-Alder cycloadditions of these dienes were carried out in the presence of the dienophiles methyl vinyl ketone, methyl propiolate, and a captodative olefin, under conditions such as solvents of high polarity, Lewis acid catalysis, and non-conventional energy sources. The reactions carried out either with mixtures of H 2 O=MeOH or under BF 3 Á Et 2 O catalysis yielded the highest regio-and stereoselectivities. The use of ionic liquids, microwaves, and ultrasound did not significantly increase the selectivity.

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