Br(?)nsted Acid Catalyzed Cascade Reactions Of Indole

Purpose:Indole and its derivatives are widely found in natural products,which have a wide range of applications in medicine,dyes and chemical industry.Br(?)nsted acid catalyzed cascade reaction has the characteristics of mild reaction conditions,high catalytic efficiency,no metal residue,simple operation and low cost,which has become an important way of indole and its derivatives synthesis.Using the indole as the substrate,Br(?)nsted acid catalyzed cascade reaction could be realized highly efficient synthesize indole derivatives.Methods:The first:Br(?)nsted acid catalyzed the cascade reaction of 3-substituted indole and α,β-unsaturated alkynone has been developed,affording 9H-pyrrolo[1,2-α]indole derivatives with high yields.The second: the Cinchona alkaloid-derived bifunctional catalysts catalyzed the cascade reaction of 3-ylidene oxindole and naphthol has been developed,affording furan[2,3-b]benzofuranone derivatives with high yields and stereoselectivities.The absolute configuration was established by using X-ray crystallographic analysis,and a possible reaction mechanism was proposed.Results:Br(?)nsted acid catalyzed the cascade reaction of 3-substituted indole and α,β-unsaturated alkynone has been developed,affording 9H-pyrrolo[1,2-α]indole derivatives with high yields(up to 94%).In addition,the Cinchona alkaloid-derived bifunctional catalysts catalyzed the cascade reaction of 3-ylidene oxindole and naphthol has been developed,affording furan[2,3-b]benzofuranone derivatives in good to excellent yields(up to 92%)and with high stereoselectivities(up to 96% ee,>20:1 d.r.).Conclusion :Br(?)nsted acid catalyzed Friedel-Crafts alkenylation/1,6-addition/condensation cascade reaction could efficiently synthesize 9H-pyrrolo[1,2-α]indole derivatives.Moreover,Cinchona alkaloid-derived squaramide catalyze the Friedel-Crafts alkylation/ hemiketalization/lactonization cascade reaction could synthesize furan[2,3-b] benzofuranone derivatives with high stereoselectivities.