| Abstract
| - Metal carbonyl salts CpW(CO)3Na,Re(CO)5Na, and CpFe(CO)2Na were usedfor intramolecularcyclization of 1-(3-bromo-1-propynyl)-2-(3-oxopropyl)benzene.Among these salts, CpW(CO)3Na wasfound to be the most effective in yielding a metalated fusedη1-2,5-dihydro-3-furyl complex. Togeneralize this cyclization, a number of organic substrates containingpropargyl bromide andtethered aldehyde or ketone were prepared. Cyclizations of thesesubstrates by CpW(CO)3Naproceeded with moderate yields (50%-65%), producing fusedtungsten−η1-2,5-dihydrofur-3-ylcompounds of five-, six-, and seven-membered rings. Demetalationsof these organometallic productsby(NH4)2Ce(NO3)6in CH3OH/CH2Cl2 underflowing CO provided fused 3-(methoxycarbonyl)-2,5-dihydrofurans; the yields were 50−60% for most cases.Consecutive oxidations of the representativeη1-2,5-dihydrofur-3-yl complex 15 to its fusedη1-2-furyl and further to η1-butenolidederivative wereaccomplished in good yields. Demetalations of these two fusedη1-heterocycles were successful forη1-butenolide but not for the η1-2-furylderivative.
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