| The reaction of iron(0) carbene complexes with hexafluorobutyne produces, 3,4-bis(trifluromethylated)furans. The reaction favored electron rich carbene complexes and yields ranged from 12-56%. Excess hexafluorobutyne was required to produce significant amounts of furan. All reactions were carried out in THF. No traces of furannulation or benzannulation were observed with Group 6 (Mo, Cr, W) Fischer carbene complexes. No trimerization or other products were isolated. The furan ring formation with hexafluorobutyne appears to be unique to iron carbene complexes. Purification was done using flash column chromatography and product formation was confirmed by 1H NMR, 13C NMR, 19F NMR and GC/MS.;A further analysis of the reaction of two different vinylketene iron(0) complexes with various 1-chloroalkynes was done which generated cycloaddition products - highly substituted catechols. The larger substituent was found predominantly in the meta position to the hydroxyl group of the phenol. THF was used for all reactions and yields ranging from 0-62% were obtained. 2-Ethoxy-3-phenylvinylketene iron(0) gives higher yields of the chlorocatechols when compared to 2-ethoxy-3-methylvinylketene iron(0). No cyclization product was isolated in the case of chloroethynyl-tributylstannane with phenylvinylketene iron(0) complexes, possibly due to the sensitivity of the product to destannylation. Further study was done by reacting 2-ethoxy-3-phenylvinylketene iron(0) with commercially available hexafluorobutyne give a 2,3-bis -trifluoromethylated phenol in 42% yield. |
