Synthesis of C-16 exocyclic dipolarophiles viz. (E)-16-arylidene estrones
In the present work, the C-16 exocyclic dipolarophiles viz. (E)-16-arylidene estrones 2 were synthesized from the reaction of estrone 1 with various aromatic aldehydes (Scheme 1). An equivalent mixture of estrone and the appropriate aldehyde were dissolved in ethanol followed by the addition of alcoholic potassium hydroxide. The mixture was boiled to reflux for 5 h and the completion of the reaction was realized when the (E)-16-arylidene estrones 2 precipitated out of the reaction mixture as yellow solid, which was filtered and washed with water. A total of fifteen (E)-16-arylidene estrones 2a–o were synthesized in almost quantitative yields (>91 %, Table 1). However, the reaction failed to occur with aliphatic aldehydes.