331 Journal of Organometallic Chemistry, 289 (1985) 331-339 Elsevier Sequoia S.A., Lausanne - Printed in The Netherlands zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONM TITANIUM-CATALYZED DIELS-ALDER CYCLOADDITION OF CONJUGATED DIENES TO BIS(TRIMETHYLSILYL)ACETYLENE. 1,2-BIS(TRIMETHYLSILYL)CYCLOHEXA-1,4-DIENE, 1,2-BIS(TRIMETHYLSILYL)BENZENE, AND THEIR METHYL DERIVATIVES K. MACH*, H. ANTROPIUSOVA, L. PETRUSOVA, F. TURE’?EK, V. HANUS, J. Heyrovskj Institute zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA of Physical Chemistry and Electrochemistry Czechoslovak Academy of Sciences, 121 38 Prague 2 (Czechoslovakia) P. SEDMERA, Institute of Microbiology, Czechoslovak Academy of Sciences, 142 20 Prague 4 (Czechoslovakia) and J. SCHRAML Institute of Chemical Process Fundamentals, Czechoslovak Academy of Sciences, 16.5 02 Prague 6 (Czechoslovakia) (Received January 3Oth, 1985) Summary The catalytic system Et ,AlCl/TiCl, induces Die&Alder cycloaddition of bis(trimethylsilyl)acetylene to 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene and (E)-1,3-pentadiene affording 1,2-bis(trimethylsilyl)cyclohexa-1,4dienes in high yields. The cyclohexadienes are readily converted to the corresponding l,Zbis(t,ri- methylsilyl)benzenes upon heating to 24O’C. Mass, infrared, ‘H, 13C and 29Si NMR spectra of all the products obtained are reported and briefly discussed. The crowded character of aromatic compounds is reflected in their mass, 13C and 29Si NMR spectra. Introduction The Diels-Alder reaction between non-polar dienes and acetylenes usually re- quires high temperature activation which in turn decreases the regio- and stereo- selectivity of the process. Highly selective cycloadditions have been carried out under mild conditions by transition metal catalysts. Nickel-catalyzed reactions have been reported to yield diene-acetylene cyclic adducts in 2/l, 2/2 and l/2 ratios, depending on the ligand field of nickel complex [l]. The l/l cyclic adducts have 0022-328X/85/$03.30 0 1985 Elsevier Sequoia S.A.