The present study concerned with the influence of the nature of the acetal fragment in unsaturated compounds on the reactivity of the C=C bond in cyclopropanation reactions with diazomethane catalyzed by copper and palladium compounds. The acetal substituents at the α or γ position with respect to the C=C bond were found to exert an activating effect on the yields of cyclopropanation products compared to the starting unsaturated carbonyl com pounds, which give 1,3 dipolar cycloaddition adducts with CH 2 N 2 as by products. Cyclo propanation of the double bonds appeared to be most efficiently catalyzed by Pd(acac) 2 .
The influence of 1,3 oxazolidine and 1,3 oxathiolane fragments in substituted alkenes on the direction of their catalytic reaction with diazomethane has been investigated. The olefins bearing an oxazolidine substituent in the α or γ position and an oxathiolane substituent in the γ position relative to the C=C bond react with diazomethane in the presence of Pd(acac) 2 selectively resulting in cyclopropanation products. The use of Cu(OTf) 2 does not result in cyclopropanation; however Cu(OTf) 2 catalyzes the reaction of diazomethane with 2 (alk 1 enyl) 1,3 oxathiolanes yielding 2,3,5,6 tetrahydro 1,4 oxathiocines formed through the [2,3] sigmatropic rearrangement of the intermediate sulfonium ylides.
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