APPROACHES TO THE SYNTHESIS OF HEPTITOL DERIVATIVES VIA IRON-MEDIATED STEREOCONTROLLED FUNCTIONALIZATION OF CYCLOHEPTATRIENONE

Stereocontrolled reduction of tropone-Fe(CO)3 (9) followed by alcohol protection gives the [(trialkylsilyl)oxy]cycloheptatriene complex 11. Osmylation of 11 proceeds with complete stereoselectivity to give the protected trihydroxycycloheptadiene complex 12, treatment of which with acid in the presence of methanol (generated in situ) gives the symmetrically trioxygenated diene complex 15. Decomplexation of these complexes, followed by stereocontrolled diene oxygenation and ring cleavage, provides methodology for the construction of heptitol derivatives. Conversion of complex 15 to ether-substituted dienyl-Fe(CO)3 cationic complexes was studied. These complexes react with nucleophiles to give diene-, dienyl-, or enediyl-Fe(CO)2L complexes, depending on the nature of the nucleophile and the spectator ligand.