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

Ring closing metathesis of pentacarbonyl[(ethoxy)(N,N-diallyl anilyl)carbene]tungsten(0) complex, [(CO)5WC(OCH2CH3)C6H4N(CH2CHCH2)2], 1 leads to the formation of pentacarbonyl[(ethoxy)(N-phenyl 2,5-dihydro pyrrolyl)carbene]tungsten(0) complex, [(CO)5WC(OCH2CH3)C6H4N (CH2CHCH2)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)5WC(OCH2CH3)C6H4R], 4–7 (4: R = OCH2CH3; 5: R = OCH2CHCH2; 6: R = OCHCHCH2CH2CH2CH2CH3; 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.

Graphical abstractN-phenyl pyrrole anchored to Fischer carbene complex has been synthesized via ring closing metathesis-oxidative aromatization of pentacarbonyl[(ethoxy)(N,N-diallyl anilyl)carbene]tungsten(0) complex, [(CO)5WC(OCH2CH3)C6H4N(CH2CHCH2)2]. In addition, a number of aryl substituted carbene complexes have also 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.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Ring closing metathesis of Fischer-type carbene complexes have been documented. ► Oxidative aromatization is the key to form heteroaromatic pyrrole ring anchored to carbene complex. ► Several aryl substituted Fischer carbene complexes have been reported.