The reaction of the allenylidene complex [Re{C/C/CPh2}(CO)2(triphos)]OTf (1) (triphos/MeC(CH2PPh2)3;OTf/OSO2CF3) with pyrazole gave the 1,2,3-diheterocyclization product [Re{C/CHCPh2(N2C3H)3}(CO)2(triphos)]Y (Y/OTf, 2OTF;Y/BPh4, 2BPh4). 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{C/CCPh2(N2C3H3)}(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.
1,3-Cycloaddition of pyrazole to the allenylidene ligand in [Re{C=C=CPh2}(CO)(2){MeC(CH2PPh2)(3)}](+)
BERTOLASI, Valerio;MANTOVANI, Nicoletta;MARVELLI, Lorenza;ROSSI, Roberto;
2003
Abstract
The reaction of the allenylidene complex [Re{C/C/CPh2}(CO)2(triphos)]OTf (1) (triphos/MeC(CH2PPh2)3;OTf/OSO2CF3) with pyrazole gave the 1,2,3-diheterocyclization product [Re{C/CHCPh2(N2C3H)3}(CO)2(triphos)]Y (Y/OTf, 2OTF;Y/BPh4, 2BPh4). 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{C/CCPh2(N2C3H3)}(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.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
