Abstract
The reaction of the allenylidene complex [Re{CCCPh 2}(CO) 2(triphos)]OTf ( 1) (triphos=MeC(CH 2PPh 2) 3; OTf= −OSO 2CF 3) with pyrazole gave the 1,2,3-diheterocyclization product [Re{CCHCPh 2(N 2C 3H) 3}(CO) 2(triphos)]Y (Y=OTf, 2OTF; Y=BPh 4, 2BPh 4 ). The molecular structure of this complex was determined by a single-crystal X-ray analysis. Treatment of 2 with sodium methoxide gave the pyrazolyl-functionalized alkynyl derivative [Re{CCCPh 2(N 2C 3H 3)}(CO) 2(triphos)] ( 3) via selective deprotonation of the vinylic hydrogen, followed by back opening of the metal-bound heterocycle. Protonation of 3 with triflic acid in dichloromethane re-generated 1 and free pyrazole. The overall result of this deprotonation/protonation sequence allowed us to propose a reliable mechanism for the formation of the 1,2,3-diheterocyclization product 2OTf.
Published Version
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