STABILIZATION OF REACTIVE ALDEHYDES BY COMPLEXATION WITH METHYLALUMINUM BIS(2,6-DIPHENYLPHENOXIDE) AND THEIR SYNTHETIC APPLICATION

Reactive aldehydes such as formaldehyde and alpha-chloro aldehydes can be successfully generated by treatment of readily available trioxane and alpha-chloro aldehyde trimers, respectively, with methylaluminum bis(2,6-diphenylphenoxide) (MAPH), and stabilized as their 1:1 coordination complexes with MAPH. The resulting CH2=O.MAPH complex reacts with a variety of olefins to furnish ene-reaction products with excellent regio- and stereoselectivities. In addition, this complex as well as alpha-chloro aldehyde-MAPH complexes can be utilized as a stable source of gaseous formaldehyde and reactive alpha-chloro aldehydes, respectively, for the nucleophilic addition of various carbanions (organometallics, enolates, etc.). Formation of reactive aldehyde-MAPH complexes is firmly confirmed by H-1 NMR spectroscopy. A space-filling model of aldehyde-MAPH complexes implies that formaldehyde and alpha-chloro aldehydes coordinated with MAPH may be electronically stabilized by two parallel phenyl groups of aluminum ligands.