Triformylferrocenes, novel modules for organometallic scaffolds

Protection of formylferrocene with propanediol under acidic conditions furn ishes its acetal. Metalation of the acetal occurs mainly in the ortho posit ion at the same ring. Reaction with N-formylpiperidine leads to the semipro tected 1,2-diformylferrocene, and the monoacetal of 1,1',2-triformylferroce ne, which can be obtained upon acidic deacetalization. Further protection o f the semiprotected 1,2-diformylferrocene with propanediol results in the c orresponding bisacetal, which is metalated to give the title compound 1,2,3 -triformylferrocene after quenching of the anion with N-formylpiperidine an d acidic deprotection. The 1,1',2-triformylferrocene undergoes an interesti ng solid-state reaction at 170 degreesC under cross-linking to yield a nove l organometallic polycondensate, while 1,2,3-triformylferrocene melts undec omposed. 1,2-Diformylferrocene was transformed into 1,2-bisbutadiynylferroc ene by treatment with Taber's reagent, followed by coupling of 1,2-diethyny lferrocene to bromo-triisopropylsilylethyne under Cadiot-Chodkiewicz condit ions in an overall 40% yield starting from diformylferrocene. (C) 2001 Else vier Science B.V. All rights reserved.