Study On The Application Of Cyclopropenone In Palladium-catalyzed [2+2+1] Domino Annulation

As an important organic synthesis reaction,carbonylation reaction is widely used in medicine,natural products,and functional materials etc.It is an increasing interest to develop of new carbonyl sources.Nevertheless,the reaction strategies of using different kinds of CO substitutes in the construction of carbonyl compounds,which including M_m（CO）_n,（CH₂O）_n,CO₂,DMF,TFBen,CHCl₃,and others,have also been developed rapidly.it is of great significance that finding new sources of carbonyl groups to realize the diversified synthesis of carbonyl compounds.In this subject,chromone fused polycyclic cyclopentanones can be efficiently constructed from 3-iodochromones and bridged olefins with cyclopropenones as the sole CO surrogate via the palladium-catalyzed[2+2+1]domino annulation.After the screening of ligands,catalysts,solvents and bases,the optimal reaction system was obtainded,affording the target product in up to 91%yield.Additionally,a series of chromone fused cyclopentanones（30 examples）were constructed in 45%～91%yields under optimal conditions.To further demonstrate the synthetic utility of the methodology,preparative-scale experiments have been performed,and proceeded smoothly to afford 6a,7,8,9,10,10a-hexahydro-7,10-methanoindeno[2,1-b]chromene-6,11-dione（4a）in 1.50 g with 83%yield and 8,11-dimethyl-6a,7,7a,11b,12,12a-hexahydro-7,12-methanobenzo[3’,4’]cyclobuta[1’,2’:5,6]indeno[2,1-b]chromene-6,13-dione（4ab）in 2.28 g with 81%yield.Moreover,4a,2-bromo-6a,7,8,9,10,10a-hexahydro-7,10-methanoindeno[2,1-b]chromene-6,11-dione（4i）and 6a,7,10,10a-tetrahydro-7,10-methanoindeno[2,1-b]chromene-6,11-dione（4x）could be further converted into various chromone derivatives under the stated conditions.Lastly,a possible reaction pathway involves a Heck coupling/C（sp²）-H activation/carbonylation sequence for the palladium-catalyzed[2+2+1]domino annulation was proposed based on our previous reports and related literatures.