Study On The Cycloaddition Of Norbornadienyl Ruthenium Complex With Alkenes/alkynes

The cycloaddition of norbornadiene(NBD) with alkenes or alkynes, in which a complex polycyclic compound is produced in one step, has been greatly developed. In these cycloaddition reactions, ruthenium complexes, especially for pentmethyl cyclopentadienyl ruthenium complexes present superior catalytic activity and numerous applications. The reactions of [Cp*Ru(H₂O)(NBD)]BF4 with various alkenes or alkynes and the mechanism of these reactions were studied, and the catalytic activity of [Cp*Ru(H₂O)(NBD)]BF₄ toward the [2+2] cycloaddition of NBD and alkynes was explored. In our work, the main results are as follows:1) A study on the Homo Diels-Alder cycloaddition of [Cp*Ru(H₂O)(NBD)]BF₄ with various alkynes was carried out. Treatment of [Cp*Ru(H₂O)(NBD)]BF₄ with phenyl acetylene, ethyl phenylpropiolate, or 4,4'-diethynyl-biphenyl at room temperature produced a [2+2+2] cycloadduct in good yield. In contrast, a similar ruthenocene complex was produced when [Cp*Ru(H₂O)(NBD)]BF4 was treated with 1,4-diphenylbutadiyne. The structures for these compounds were characterized by 1^H NMR, (13)^C NMR spectra and X-ray diffraction.It is expected that these Homo Diels-Alder cycloaddition via the intermediate [Cp*Ru(RC=CR)(NBD)]⁺. The outcome of the reaction is strongly affected by the structures of the alkynes and NBD.2) In the course of using [Cp*Ru(H₂O)(NBD)]BF₄ to catalyze the dimerization of NBD, we found the ruthenocene complexes were formed. The process begins with the rearrangement of a coordinated NBD ligand to a vinylcyclopentadiene group, and then the vinyl group undergoes [2+2] cycloaddition reaction with NBD.