69016-33-7Relevant academic research and scientific papers
Novel synthesis of (d,l)-cis-chrysanthemic acid involving α,α′-dibromination of 2,2,5,5-tetramethylcyclohexane-1,3-dione: application to the enantioselective synthesis of (1R)-cis-chrysanthemic acid
Krief, Alain,Dumont, Willy,Kremer, Adrian
, p. 2398 - 2401 (2009)
cis-Chrysanthemic acid has been prepared in a few steps from dimethyldimedone via dibromination at alpha positions of each carbonyl carbons. The trans-dibromide which is almost exclusively formed has been isomerized to its cis-stereoisomer by highly chemoselective tandem H/K-K/H exchanges involving potassium bases at low temperature (-40 °C). Carbocyclization of the potassium enolate intermediate takes place at around -30 °C and provide the bicyclo[3.1.0]-hexane skeleton. Lithiated bases behave differently and mainly lead to Br/M rather than to H/M exchange. We have been unsuccessful in using state of the art enantioselective metallation reactions to achieve the enantioselective synthesis of (1R)-cis-chrysanthemic acid using the disclosed strategy. This therefore still remains challenge.
