STRUCTURE - ACTIVITY RELATIONSHIPS IN SOME HERBICIDAL FLUORENE DERIVATIVES

Abstract

Synthetic plant-growth regulators derived from fluorene-9-carboxylic acid ('morphactins') are introduced and the literature on them is reviewed. Similar herbicidal activity has been found with 9,9-bishydroxymethylfluorene, a compound which can be obtained directly from the hydrocarbon fluorene. There follows a detailed review of the chemistry of fluorene and 9,9- bishydroxymethylfluorene. 9-Substituted and ring-substituted derivatives of this diol have been synthesised and their chemistry and biological activity are discussed. The hydroxymethylation of substituted fluorenes is possible on a small scale in suitable solvents which do not stabilise the corresponding radical anions. This radical anion formation, when it occurs, seriously reduces the yield of hydroxymethylated product. Acetonitrile as solvent and aqueous benzyltrimethyl ammonium hydroxide as base were found to be a particularly useful system for these reactions. Methyl 2-chloro-9-hydroxymethylfluorene-9-carboxylate was found to be the most active compound synthesised. It was concluded that a 9-carboxylic acid group is required for high activity. None of the compounds examined were found to be more active than 'chlorflurecol’, the commercial product.