Synthesis and characterization of N-phenyl pyrrole anchored to Fischer carbene complex through ring closing metathesis oxidative aromatization and various aryl substituted Fischer carbene complexes

Abstract

Ring closing metathesis of pentacarbonyl[(ethoxy)(N,N-diallyl anilyl)carbene]tungsten(0) complex, [(CO)₅Wdouble bond; length as m-dashC(OCH₂CH₃)C₆H₄N(CH₂CHdouble bond; length as m-dashCH₂)₂], 1 leads to the formation of pentacarbonyl[(ethoxy)(N-phenyl 2,5-dihydro pyrrolyl)carbene]tungsten(0) complex, [(CO)₅Wdouble bond; length as m-dashC(OCH₂CH₃)C₆H₄N (CH₂CHdouble bond; length as m-dashCH₂)₂], 2 in good yield. Further, complex 2 undergoes oxidative aromatization to afford N-phenyl pyrrole anchored to alkoxy carbene, 3. In addition, a number of aryl substituted carbene complexes [(CO)₅Wdouble bond; length as m-dashC(OCH₂CH₃)C₆H₄R], 4–7 (4: R = OCH₂CH₃; 5: R = OCH₂CHdouble bond; length as m-dashCH₂; 6: R = OCHdouble bond; length as m-dashCHCH₂CH₂CH₂CH₂CH₃; 7: OC₆H₅Br) have been synthesized from the reaction of 1-(allyloxy)-4-bromobenzene with W(CO)₆ in presence of various concentration of n-BuLi and Meerwein's salt. All the complexes have been isolated in moderate to good yields and have been characterized by ¹H NMR, ¹³C NMR, IR, UV–vis spectroscopic techniques and the solid state structures of 1, 2 and 4 have been unequivocally established by X-ray diffraction analysis.