Faculté des sciences

An Unexpected Tandem Reaction between N-Butadienyl-N-alkylketeneN,0-Trimethylsilylacetals of Propionamide and Activated Dienophiles like N-Phenylmaleimide or Acryloyl Chloride

Baak, Marcel ; Rubin, Yves ; Franz, Andreas ; Stoeckli-Evans, Helen ; Bigler, Laurant ; Nachbauer, Jürgen ; Neier, Reinhard

In: Chimia, 1993, vol. 47, p. 233-240

Starting from the N-butadienyl-N-alkylpropionamides 1a-1c the corresponding N,0-trimethylsilylacetals could be obtained using the mixture ofLDA and trimethylsilyl chloride in THF. The unexpected reaction sequence Diels-Alder reaction/acylation between the N-butadienyl-N-alkylketene N,0-trimethylsilylacetal ofpropionamide (2a-2b) and... Plus

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    Summary
    Starting from the N-butadienyl-N-alkylpropionamides 1a-1c the corresponding N,0-trimethylsilylacetals could be obtained using the mixture ofLDA and trimethylsilyl chloride in THF. The unexpected reaction sequence Diels-Alder reaction/acylation between the N-butadienyl-N-alkylketene N,0-trimethylsilylacetal ofpropionamide (2a-2b) and N-phenylmaleimide produced tricyclic products rac-5a -rac-5b and bicyclic products rac-6a - rac-6b with high diastereoselectivity. The reaction of the N,0-trimethylsilylacetals 2a and 2c with acryloyl chloride in a similar sequence gave the bicyclic products rac-8a and mc-8c. The stepwise synthesis of bicyclic systems of this general structure could only be successfully executed in 26 yield treating the Diels-Alder product rac-10 with LDA.