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The series of dinuclear to nonanuclear all-ortho methylene-bridged oligophenols 2 -9 has been synthesized according to a repetitive reaction sequence involving the C-ortho regiospecific condensation of appropriate phenoxymagnesium precursors with salicyl alcohol or paraformaldehyde. IR, UV, mass, 'H and I3C NMR characteristics of these oligomers are discussed. X-ray crystal structures of 2, 3, and 4 are also reported.

The reactions between formaldehyde and a series of aryloxymagnesium bromides (1 ) and their complexes with hexamethylphosphoramide (HMPA) in benzene have been investigated. In the absence of ligand 2.2'-dihydroxydiphenylmethanes (2) are obtained, while in the presence of stoicheiometric amounts of HM PA Z-hydroxybenzaldehydes (4) are produced in high yield. Both products are the result of an exceptional ortho-regioselective attack on the aromatic nucleus of the phenol. The formation of (4) has been shown to occur via an oxidationreduction process, promoted by HM PA, between the 2-hydroxybenzyl alcohol intermediate ( 5) and formaldehyde.The difference in acidity between the free and HMPA-complexed magnesium counterion is invoked to explain the two reaction pathways.IN spite of the enormous amount of work done on the reaction between phenols and formaldehyde due to its industrial importance, no great success has been achieved so far in the control of its regioselectivity and of the RESULTSThe production in high yield (Table 1) of 2,2'-dihydroxydiarylmethane derivatives (2) by means of two successive ortho-regioselective reactions on the aromatic nucleus of the TABLE 1 Reaction of aryloxymagnesium bromide, RMgBr ( l ) , with formaldehyde (0.5 equiv.) in refluxing benzene (20 h)R (la) Phenoxy (1 b) 2-Methylphenoxy (Ic) 3-Methylphenoxy (Id) 4-Methylphenoxy (le) 2-isopropylphenoxy (If) 2-t-Butylphenoxy (lg) 2,3-Dimethylphenoxy (lh) 3,5-Dimethylphenoxy (li) 2-t-Butyl-5-methylphenoxy ( l j ) 4-Methoxyphenoxy (lk) 4