ORGANOMETALLIC SYNTHONS - WITTIG REACTION OF TRICARBONYL[(3,4,5,6-ETA)-1,3,5-CYCLOHEPTATRIENE-1-CARBOXALDEHYDE]IRON

The utility of the Wittig reaction in synthesis of organometallic compounds is exemplified by its application to the preparation of a series of tetraene-Fe(CO)3 complexes from aldehyde 9 and a variety of triphenylphosphoranes. Reaction of 9 with triphenylmethylene phosphorane afforded unexpectedly a 1 1 isomeric mixture of 8-methylheptafulveneiron tricarbonyl (12), probably via a (1,9) hydrogen shift of intermediate 11. Triphenylbenzylidene phosphorane condensed with 9 to give the cis and trans isomers of cycloheptatrienyl-styrene complex 14. The triphenylphosphoranes of carbomethoxymethylene, carboethoxymethylene and cyanomethylene react with 9 yielding the appropriate trans condensation products exclusively. Tetracyanoethylene (TCNE) and N-phenyltriazolinedione (NPTD) readily react periselectively with the unrearranged Wittig reaction products at the free diene moiety, affording the corresponding 4+2 cycloadducts. Heptafulvene complex 12, upon reaction with TCNE, gave the 8+2 cycloadduct 26. © 1979.