Published January 1, 2013 | Version v1
Journal article Open

Stereoconvergent Generation of a Contrasteric syn-Bicyclopropylidene (=syn-Cyclopropylidenecyclopropane) by Stille-Like Coupling

  • 1. Ataturk Univ, Fac Sci, Dept Chem, TR-25240 Erzurum, Turkey
  • 2. Middle E Tech Univ, Fac Sci, Dept Chem, TR-06800 Ankara, Turkey
  • 3. Univ Ca Foscari Venezia, Dipartimento Chim, I-30123 Venice, Italy

Description

Stereoisomerically pure endo- and exo-7-halo-7-(trimethylstannyl)benzonorcar-3-enes (=endo- and exo-(1-halo-1a,2,7,7a-tetrahydro-1H-cyclopropa[b]naphthalen-1-yl)trimethylstannane) 4 and 6 were selectively obtained by lithiumtin or magnesiumtin transmetalation in good yields (Scheme2 and 3). The reaction of these compounds with copper(I) thiophene-2-carboxylate (CuTC) produced in both cases the corresponding CS-symmetric bicyclopropylidene (=cyclopropylidenecyclopropane) syn-1, a single diastereoisomer (Schemes5 and 6). The structure of syn-1 was undoubtedly elucidated by X-ray single crystal diffraction. The coupling mechanism of the carbenoid cyclopropane is discussed (Scheme7).

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