APPLICATION OF THE DOUBLE PAUSON-KHAND CYCLIZATION TO THE SYNTHESIS OF BIS(CYCLOPENTADIENES) - PREPARATION OF PHENYL-BRIDGED BIS(TETRAHYDROINDENYL)TITANIUM AND ZIRCONIUM DICHLORIDES

We have demonstrated a very efficient (5 steps, 28% yield from 1-octen -7-yne and 1,2-diiodobenzene) and novel synthesis of 1,2-bis(9-bicyclo [4.3.0]-non-1,6-dienyl). We utilized for the first time in a bis(cyclo pentadiene) synthesis the double Pauson-Khand cyclization and Shapiro- elimination methods. The double Pauson-Khand cyclization is also succe ssful in the preparation of ethylene-bridged bis(cyclopentadienes). A novel iodine-promoted elimination of allyl methyl ethers was also appl ied in the preparation of bis(cyclopentadienes). The solid state struc ture of yclo[4.3.0]-non-1,6-dienyl)benzenedichlorotitanium (dl-4a) was obtained and it shows a very obtuse angle between the cyclopentadieny l substituents. The crstallographic data for dl-4a are as follows: C24 H24Cl2Ti, monoclinic, C2/c. a = 15.805(3) Angstrom, b = 11.027(2) Angs trom, c = 13.323(3) Angstrom, beta = 121.40(3)degrees, volume 1981.9 A ngstrom(3), Z = 4, R = 4.41, R(w) = 6.92%, goodness of fit 2.96.