Eine stereospezifische Synthese von <i>syn</i>‐Bishomochinon über <i>p</i>‐Benzochinon‐bis(äthylen)ketal

Abstract

Abstract The bis(ethylene)ketal of p ‐benzoquinone ( 6 ) has been prepared from the bis(ethylene)ketal of cyclohexane‐1,4‐dione ( 3 ) by bromination with bromine in ether followed by dehydrobromination with potassium t ‐butoxide. Two intermediate dibromides ( 4 and 5 ) were isolated and their constitutions as well as their configurations determined from spectroscopic properties. Partial hydrolysis of 6 furnished the mono(ethylene)ketal of p ‐benzoquinone ( 9 ), which was converted stereospecifically to syn ‐bishomoquinone ( 2 ) by the double addition of sodium dimethylsulfoxonium‐methylide. The intermediate mono(ethylene)ketals of syn ‐bishomoquinone ( 11 ) as well as of the mono(methylene) addition product ( 10 ) were also isolated.