NICKEL(0)-CATALYZED CYCLOADDITION OF SILYL DIYNES WITH CARBON-DIOXIDE TO SILYL BICYCLIC ALPHA-PYRONES

Mono- and bicyclic a-pyrones are useful intermediates in organic synthesis.1 Furthermore monocyclic and an-nulated a-pyrone ring systems are found in several biologically active natural products.la-c Thus it is interesting to develop a convenient synthetic method for function-alized a-pyrones. A silyl-substituted a-pyrone is attractive because the silyl substituent attached to an sp2-carbon atom is known to be easily converted into a variety of functional groups,2 i.e., halogen, acyl, and hydroxy groups3 along with a hydrogen atom. Examples of the synthesis of silyl a-pyrones, however, are few. Formation of 3- and 5-(trimethylsilyl)-substituted 6-ethoxy-4-methyl-a-pyrones by the rhodium-catalyzed carbonylation of 1-carbethoxy-3-methyl-2-(trimethylsilyl)cyclopropene has been described. © 1990, American Chemical Society. All rights reserved.