Synthesen von (1<i>R</i>)‐<i>cis</i>‐3‐(2′,2′‐Dihalovinyl)‐2, 2‐dimethylcyclopropan‐carbonsäuren <i>via Favorskii</i>‐Umlagerung von optisch aktiven Cyclobutanonen

Abstract

Syntheses of (1 R )‐ cis ‐3‐(2′,2′‐Dihalovinyl)‐2,2‐dimethylcyclopropane Carboxylic Acids via Favorskii ‐rearrangement of Optically Active Cyclobutanones The cis ‐cyclobutanones 7 are resolved by means of optically active amine salts of their sodium hydrogen sulfite adducts. The desired (1 R )‐ cis ‐carboxylic acids 9 are obtained from the (+)‐ cis ‐cyclobutanones 7 via Favorskii ‐rearrangement and HX‐elimination. The recycling of undesired (−)‐ cis ‐cyclobutanones 7 is carried out in good yield by their racemization, thus rendering the total synthesis 1 + 2 → 9 chirally economic.