Hans Greuter

Fluorine-containing organozinc reagents. V.: The reformatskii-claisen reaction of chlorodifluoroacetic acid derivatives

Abstract Silicon induced Reformatskii-Claisen reaction of allyl chlorodifluoroacetate ( 1 ) affords 2,2-difluoro-4-pentenoic acid ( 2 ) in good yields. Starting from inexpensive chloro-difluoroacetic acid, a variety of useful fluorine-containing synthetic building blocks can be obtained under the same reaction conditions.

Intramolecular [2+2] Cycloadditons of Ketenes and Olefins

The synthetic potential of the intramolecular ketene cycloaddition is presented. It proves to be a versatile method for the synthesis of a variety of bi- and tricyclic cyclobutanones. The major side reaction, namely the dimerization of the ketene is prevented by the introduction of conformational restrictions. This has been achieved by an additional double bond or by an annulated ring system. Following this strategy C-analogues of a penem and a carbapenem as well as linear and angular annulated triquinanes are obtained in high yield.