Cyclopropyl Building Blocks for Organic Synthesis.Part 19. Versatile Syntheses of Alkynyl-and Substituted Alkynylcyclopropanes:2-Alkoxyethynylcyclopropanes for the Anellation of Bicyclo(3.3.0)octane Fragments.-Alkynyl-and substituted alkynylcyclopropanes are prepared from the enol ethers (I) which are brominated and coupled with propargyl magnesium bromide (II). The protected compounds (V) undergo cyclization to produce the cyclopropanes (VI) and (VII). The lithio derivative of (VIa) and (VIIa) reacts with electrophiles such as (X) with retention of configuration on the three membered ring. (VIIIb) and (IXb) can be used to anellate a bicyclo(3.3.0)octane fragment onto a cycloalkene such as (XIII). -(MILITZER, H.-C.; SCHOEMENAUER, S.; OTTE, C.; PULS, C.; HAIN, J.; BRAESE, S.; DE MEIJERE, A.; Synthesis (1993) 10, 998-1012; Inst. Org. Chem., Univ. Hamburg, D-20146 Hamburg, Germany; EN)
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