“…Among the available publications on this subject, of particular note is a series of works on the photochemical codimerization of CHT with alkenes, alkynes, and dienes in the presence of chromium complexes [2] and cycloaddition catalyzed by titanium [3] cobalt [4], and rhodium compounds [5]. In addition, polycyclic adducts based on CHT are valuable precursors in the synthesis of a number of compounds having high biological activities [6].Previously, we have developed the efficient methods for the selective cycloaddition of 1,2-dienes and acetylenes [7], 7-spirocyclopropylnorborna-2,5-dienes [8], a,u-diallenes, and a,udiacetylenes [9] to CHT in the presence of catalytic systems based on titanium complexes.As the development of these studies and in order to extend the scope of applicability of our method for the synthesis of polycyclic compounds of unique structure, we performed for the first time the [6pþ2p]-cycloaddition of Si-containing alkynes to 7-substituted CHT catalyzed by Ti(acac) 2 Cl 2 eEt 2 AlCl.The reaction of 7-alkyl(phenyl,allyl)-1,3,5-cycloheptatrienes with alkynes 1a-j taken in 1:1 M ratio catalyzed by the Ti(acac) 2 Cl 2 eEt 2 AlCl system carried out in benzene for 8 h at 80 С affords bicyclo[4.2.1]nona-2,4,7-trienes 2a-j in 79e88% yields, which were isolated by column chromatography (elution with petroleum ether) (Scheme 1) [15]. The addition of alkyne to the cycloheptatriene system occurs in the stereoselective manner to give mainly the syn-isomer.…”