Reactions of 2-chloro-NN-diethyl-1,1,2-trifluoroethylamine with alcohols. Part 3. In the presence of lithium chloride; preparation of chlorogibberellins

Abstract

The reactions of gibberellin derivatives with 2-chloro-NN-diethyl-1,1,2-trifluoroethylamine in the presence of lithium chloride have been investigated in several different solvents. In all cases the bridgehead hydroxy-group was smoothly replaced by chlorine; in gibberellic acid and its esters a 4β-chloro-substituent was also introduced, but if ring A was saturated the 2β-hydroxy-group was eliminated. When the reaction was carried out in tetrahydrofuran or 1,2-dimethoxyethane as solvent, nucleophilic attack at the bridgehead by the oxygen of the ether also took place to give 7-alkoxygibberellins in 10–30% yield. 4β,7-Dichloro- and 7-chloro-4aα-hydroxy-1β,8-dimethylgibbane-1α,10β-dicarboxylic acid 1,4a-lactones (19) and (20), respectively, and 7-chloro-4aα-hydroxy-1β,8β-dimethylgibb-2-ene-1α,10β-dicarboxylic acid 1,4a-lactone (38) have been prepared and preliminary bioassay results are discussed.