Scrabbling around in Synthetic Nuances Managing Sodium Compounds: Bisphenol/Bisnaphthol Synthesis by Hydroxyl Group Masking

A unique method of bisphenol/bisnaphthol synthesis is being proposed, serendipitously discovered in the course of the careful analysis of an aminophenol methylation reaction. The insightful exploration of the synthesis of N- or O-methylated species, originating from functionalized phenols obtained by a conventional strategy, provided the opportunity to discover an unexpected reaction pathway yielding various bisphenols. Sodium complexes were found to be crucial intermediates in the synthetic scenario. Their formation, which is usually an imperceptive step, was substantial for the productive outcome of functional group protection. Thorough exploration revealed an essential structural motif of aminophenolate, necessary for the successful outcome of the reaction, and also enabled establishing the limitations of the new method. The work demonstrated that a slight change in the perspective and close inspection of the synthetic nuances can answer the important question concerning what a specific target-oriented synthesis strategy is lacking.

The protection of the hydroxyl group of aminophenols with use of MeI—a general and, in many cases, excellent methylation reagent—was investigated. In-depth understanding of the mechanistic aspects of methyl protective group incorporation provided a practical guide for its application in organic synthesis, but it also opened a new route for the synthesis of an original group of bisphenols.