Radical Tandem Cyclization Reactions Based On Biaryl Vinyl Ethers

Benzo[c]chromene skeletons are widely present in natural products,drug molecules and materials,and play an important role in organic synthetic chemistry due to the wide reactivity of aromatic heterocycles.Therefore,synthetic routes for the construction of heterocyclic compounds are of interest to organic and pharmaceutical synthetic chemists.This paper mainly studies the synthesis of corresponding benzo[c]chromene derivatives based on radical tandem cyclization of biaryl vinyl ethers under different conditions.The specific reaction is as follows:1.The radical tandem cyclization of biaryl vinyl ether and acetonitrile by microwave irradiation was developed to obtain 3-（6H-Benzo[c]chromen-6-yl）propionitrile.In this reaction,BPO（3 equiv）was used as the oxidant,acetonitrile as the solvent and reagent,and the reaction was completed by heating to 100°C for 20 min in a microwave reaction synthesizer,realizing the C（sp~3）-H activation of acetonitrile.The reaction substrate has good functional group tolerance,simple and rapid reaction conditions,and good product yield.2.The radical tandem cyclization of biaryl vinyl ether and acetone by microwave irradiation was developed to obtain 4-（6H-Benzo[c]chromen-6-yl）butan-2-one.In this reaction,BPO（3 equiv）was used as the oxidant and acetone as the solvent and reagent.The reaction was heated to 100°C for 20 min in a microwave reaction synthesizer,and the C（sp~3）-H activation was achieved.The reaction substrate has good functional group tolerance,simple and rapid reaction conditions,and good product yield.3.Using biaryl vinyl ether as substrate,sodium aryl sulfinate as reactant,Ag NO₃（20mol%）as catalyst,K₂S₂O₈（2 equiv）as oxidant,DMF and water（2:1）were studied.A method for the efficient synthesis of 6-（Toluenesulfonylmethyl）-6H-benzo[c]chromene derivatives under the condition of heating at 120°C for 3 h.Under the optimized reaction conditions,the corresponding products were produced in good yields and the sulfonyl groups could be efficiently introduced directly into the substrates.