80. “A convenient synthesis of dibenzo[a,c]cyclooctene based on thioenol ether reduction”
    André Lottaz, P.; Edwards, T. R.; Mentha, Y. G.; Burger, U.
    Tetrahedron Lett. 1993, 34, 639-642.

9,10,11,12-Tetrahydrodibenzo[a,b]cyclooctane-9,12-diol (6) is found to be reluctant to double bond forming elimination. It gives a bridge ether (7) instead. The corresponding diketone (5) reacts with benzyl mercaptan to provide the bis-thioenol ether (8-a. The latter, upon treatment with Raney nickle, gives the desired title diene 1. An alternative approach to 1, based on repeated carbane addition to phenanthrene, is also presented.

DOI : 10.1016/S0040-4039(00)61640-4 

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