Annulation Cascades Of Enynes Or Alkynes For The Synthesis Of Polycyclic Compounds

Polycyclic compounds are widely found in natural products,drugs and functional materials,and are closely related to people’s production and life.The development of efficient methods for the synthesis of polycyclic compounds has been a research hotspot in organic synthesis.Although methods for the synthesis of polycyclic compounds have made a breakthrough in recent years,examples for targeting polycyclic skeleton construction in one step are rare.This paper aims to develop new methods for preparing polycyclic compounds in one step,thereby overcoming the problems existed in the traditional synthesis process of polycyclic compounds and providing new idea,efficient accesses to polycyclic compounds.The main contents of this paper are as follows:1.The challenges and development tendency in the synthesis of polycyclic compounds are firstly introduced.Moreover,recent progress in the applications of the cascade reactions for the synthesis of polycyclic compounds has also disclosed,where some reaction mechanisms were also discussed.2.A palladium-catalyzed annulation of 1,6-enyne via a 6-exo-trig fashion was developed.By using Pd（OAc）₂ as catalyst,t BuONO as oxidant,and 1,2-dichloroethane as solvent,a series of potentially medicinal valuable bridge ring compounds were synthesized with high selectivity at room temperature under air atmosphere;The reaction features mild conditions,broad substrate scope,excellent functional group tolerance and simple post-treatment.3.A[2+2+2]annulation of 1,n-enynes with azobis（alkyl nitrile）s using CuBr₂ as catalyst,n Bu₄NOAc as additive and H₂O/MeCN as solvent at 85°C was established.A variety of phenanthridinedione derivatives were synthesized efficiently.Control experiments show that the reaction includes a free radical process.The ¹⁸O isotope labeling experiment verifies the source of carbonyl oxygen atoms in the resulting products.4.A CuSO₄-catalyzed[2+2+2]cycloaddition reaction ofα-bromo-o-ethynylarylcarbonyl compounds with alkynes for efficiently producing various benzo[de]quinolinone derivatives is reported in the presence of TPMA ligand,potassium carbonate base,potassium iodide additive and trifluorotoluene solvent.Selective split of the C-Br bond is achieved by changing the ligands.Control experiments suggest that the reaction proceeds via a radical process,and the bromide-transfer intermediate is not the key intermediate for the reaction.