Studies On Bronsted Acid Catalyzed Cyclization Of 1,6-Enynes

The chemical behavior of 1,6-enyne substrate via transition metal catalyst has been extensively studied. The 1,6-enyne cycloisomerization gets the following characteristics:starting from the open chain substrate can be efficiently synthesized cyclic compounds; with atom economy; can easily obtain the 1,3-and 1,4 diene product.These features attracted the interest of chemists. After nearly two decades, this type of reaction has been great development. Up to now, scientists has developed a variety of transition metal catalyst system. And the difference of the regional selectivity, stereoselectivity lead to different reaction results.The key of this paper is that different from the traditional transition metal catalysis, researching on Br(?)nsted acid catalyzed 1,6-enyne cycloisomerization by high efficiency and convenient reaction. The divinyl product was found for the first time.2.0 mmol of 1,6-enyne with 0.1 mol% of catalyst in DCM (2.0 mL) at 0℃. In the involvement of water molecules, the 1,6-enyne was cycloisomerizedto give series of divinyl products, and the yield was in 56%-84%, respectively. The structures of products were further confirmed by from IR,1H NMR,13C NMR spectras and elemental analysis. In addition, on the basis of the electrons and structures of products, we established the mechanism of this reaction in an experimental manner:hydrogen protons through the provision of Bronsted acid activation of acetylene base, induced alkenyl as nucleophilic attack, and complete the ring of ring-diene derivatives generated together.