Hydrogenation of cyclobutanes in strained cage compounds. Synthesis of ditwistane and bisnorditwistane (ditwistbrendane)

Abstract

The central bond of the bicyclo[2.2.0]hexane system of the dimeric cage compound synthesized photochemically from N-chloroacetyltyramine was hydrogenated with 10% Pd–C to give the dihydro-compound. Similarly 7,10-dihydroxy-1,4,7,10-tetramethylpentacyclo[6.4.0.0^2,5.0^3,12.0^4,9]dodecane-6,11-dione gave 6,12-dihydroxy-2,6,9,12-tetramethyltetracyclo[6.2.2.0^2,7.0^4,9]dodecane-5,11-dione, and its spectral data revealed the correct structure, which was confirmed by the X-ray analysis. This hydrogenation was extended to the synthesis of [8]-ditwistane and bisnorditwistane (ditwistbrendane). Thus, pentacyclo[6.4.0.0.^2,50^3,12.0^4,9]dodecane-6,11-dione synthesized from salicyl alcohol was hydrogenated to give ditwistanedione. Dithioketalization and desulphurization gave ditwistane. All the rings of this compound are six-membered and in the distorted twist-boat conformation. Similarly, hydrogenation of pentacyclo[5.3.0.0^2,5.0^3,10.0^4,8]decane and its 6-one gave bisnorditwistane.