A novel rearrangement reaction: single-step conversion of 2-(6-carboxy-3-oxoheptyl)-3,4-dihydro-6-methoxynaphthalen-1 (2H)-one into 1-(3-carboxybutyl)-2-(2-carboxyethyl)-3,4-dihydro-6-methoxynaphthalene

Abstract

The synthesis of 2-(2-carboxyethyl)-1-(3-carboxypropyl)-3,4-dihydro-6-methoxynaphthalene (28) and the homologous diacid (30) has been achieved in a single step from the 2-(6-carboxy-3-oxoalkyl)-3,4-dihydro-6-methoxynaphthalen-1(2H)-ones (22) and (24), respectively, via a novel acid-catalysed cyclisation–rearrangement reaction. The structure of the diacids (28) and (30) is supported by the high resolution mass spectrometric data of their respective dimethyl esters (29) and (31). The aromatic methoxy-group and the carboxy-function at C-6 in the side chain are critical for the rearrangement, but not for the cyclisation, part of the reaction. Based on this and other observations a mechanism for this novel rearrangement reaction has been proposed.