HIGHLY EFFICIENT RING-CLOSURE OF AROMATIC DIALDEHYDES TO MACROCYCLIC ALLENES

The one-pot double deoxygenation of simple alkyl- and polyether-tether ed aromatic dialdehydes to give macrocyclic allenes has been accomplis hed in extraordinarily high yield without the need for slow-addition t echniques, using a Ti(IV)-substituted ylide reagent and bis(trimethyls ilyl)amide bases. Diastereoselective allene formation occurs when a bi naphthyl unit is present in the substrate backbone, and the resulting cyclic allene is characterized by X-ray diffraction. Highly efficient cyclization is proposed to be the result of a combination of preorgani zation about the amide base counterion and a low concentration of the immediate precursor to Wittig-style olefination ring closure.