Stereoselective synthesis of spiro and condensed pyrazolines of steroidal α,β-unsaturated ketones and nitrilimines by 1,3-dipolar cycloaddition

摘要: Abstract Effective syntheses of endo- and exocyclic α,β-unsaturated ketones as C dipolarophiles were carried out in the 13α-estrone series. The 1,3-dipolar cycloadditions 15,16α,β-unsaturated 3-methyl 3-benzyl ether with nitrilimines stereoselectively furnished two regioisomers new condensed pyrazolines a ratio 2:1. main product was isomer obtained by attack N-terminus 1,3-dipole on carbon atom β to carbonyl group dipolarophile. nitrilimine 16-methylene-17-ketones stereo- regioselectively spiropyrazolines. dipole occurred α-carbon ketones. reactions performed under both homogeneous heterogeneous conditions. Silver acetate base proved more effective than its triethylamine counterpart. Changes regio- stereoselectivities not observed variation conditions cycloaddition reactions. structures products determined NMR (one- two-dimensional) MALDI TOF MS techniques, C70 fullerenes matrix latter case.