Pd?OAc?₂-Catalyzed Cyclization Reaction Of Baylis-hillman Adducts

Baylis-Hillman adducts is one kind of new stereocenters and has proven to be a very useful carbon-carbon bond-forming method in the synthesis of highly functionalized molecules.Palladium-catalyzed chemical transformations of modified Baylis-Hillman adducts started very recently,but have already provided many interesting results.This dissertation has made collective references on the synthesis methods of coumarin,Baylis-Hillman reaction,the palladium-catalyzed reactions of Baylis-Hillman adducts,the palladium-catalyzed cyclization reaction,the palladium-catalyzed synthesis of coumarin.Two cyclization reactions of Baylis-Hillman adducts catalyzed by Pd(OAc)2 has been developed.Part 1:10 Aryl allyl ethers were synthesized in good yields by acetylation?bromation and the reaction with phenols with K2CO3 as the base?actone as the solvent at reflux condition.Part 2:10 3,4-dihydrocoumarin derivatives were obtained by cyclization of aryl allyl ethers in the presence of Pd(OAc)2/Cu(OTf)2.The reaction was taken under reflux condition with 1,2-Dichloroethane as the slvent?5 mol%Pd(OAc)2?5 mol%Cu(OTf)2 as the catalyst.This cyclization reaction shows some advantages in terms of its simple operation,easily available and afford the products in moderate good yields.Part 3:Baylis-Hillman acetates were synthesized from Baylis-Hillman adducts.A number of indene derivatives were synthesized under the catalysis of Pd(OAc)2/Cs2CO3/PPh3/dioxane from Baylis-Hillman acetates.The reaction and the scope of the process were examined,it was taken under protection of Ar2,1,4-dioxane as the solvent,5 mol%Pd(OAc)2,10 mol%PPh3 as the catalyst,lequ Cs2CO3 as the base.In conclusion,two cyclization reactions of Baylis-Hillman adducts catalyzed by Pd(OAc)2 have been developed.These two methods expand the application of Baylis-Hillman adducts and the palladium-catalyzed reactions in the organic chemistry.