Low-valent Niobium Catalyzed Efficient Transformation Using Simple Alkenes

过渡金属催化的不饱和化合物的[2+2+2]环加成反应已被广泛研究，用于形成各种芳香族和不饱和环状化合物。本文报道了热稳定性较好的低价Nb（III）化合物NbCl_3（DME）或NbCl_5/（TMS）_3SiH作为催化剂，催化端炔、内炔和烯烃的多组分偶联[2+2+2]分子间环加成反应，以优异的产率和化学/区域选择性合成1，3-环己二烯衍生物。

Transition-metal-catalyzed[2+2+2] cycloaddition of unsaturated compounds has been extensively studied for the formation of various aromatic and unsaturated cyclic compounds. In this study, we reported that thermally stable low-vallent Nb(III) compounds, NbCl_3(DME) or NbCl_5/(TMS)_3SiH provide as an efficient catalysts for the multi-component coupling[2+2+2] intermolecular cycloaddition reaction of terminal alkynes, internal alkynes and alkenes leading to 1, 3-cyclohexadiene derivatives as the desired products in excellent yield and chemo/regioselectivity.