Synthesis Of Cyclopentadienyl Alkyl Ethers Via Pdcatalyzed Cyclotrimerization Of Diarylacetylenes

A novel efficient tandem cyclization–methoxylation reaction has been firstdeveloped to synthesize cyclopentadiene ethers via palladium-catalyzed trimerizationof diarylethynes. Using the discovered method, the traditional synthesis steps of thearyl substituented cyclopentadiene ethers were simplified with mild conditions.1. The reaction was carried out with5mol%Pd(OAc)2as the catalyst in MeOH(or EtOH) at60oC for24hours. A series of cyclopentadiene ether compounds wereobtained in moderate to good yields.2. The reaction mechanism was proposed based on Q-Tof APCI-HRMS resultsand some important reaction intermediates have been found. It supposed that thereaction went through the rearrangement of the1-palladacycloheptatriene whichgenerated by the cyclotrimerization reaction via palladiumcatalyzed of diarylethynes,then the elimination of one dimethoxymethyl benzene molecule to accesscyclopentadiene ethers.3. The fluorescent properties of the obtained compounds were studied both inthe solid state and in solution.