Reactions of 2-chloro-NN-diethyl-1,1,2-trifluoroethylamine with alcohols. Part 4. In the presence of lithium bromide and dimethyl sulphide: preparation of bromo- and methylsulphinyl-gibberellins

Abstract

Tetrahydrogibberelllc acid (1) was treated with 2-chloro-N,N-diethyl-1,1 -2-trifluoroethylamine in the presence of lithium bromide to give inter alia 7α-bromo-4aα-hydroxy-1β,8β-dimethylgibb-2-ene-1α,10β-dicarboxylic acid 1,4a-lactone (10); its dihydro-derivative was active in the Tanginbozu dwarf rice bioassay. When the reaction was carried out on methyl tetrahydrogibberellate (2) in dimethyl sulphide and the products were oxidized, they included 10β-methoxycarbonyl-1β,8β-dimethyl-7α-methylsulphinylgibb-2-ene-1α,4aα-carbolactone (20).