Both 2,2-dibromocyclobutanones and 2,2-dichlorocyclobutanones were synthesized in order to compare their ability for ring expansion towards 3-pyrrolinones. The synthesis of these small ring compounds involves a [2+2]-cycloaddition of in situ generated dihalogenated ketenes to substituted styrenes. [12] [13] In contrast to the synthesis of 2,2-dibromocyclobutanone, which is a more laborious and low yielding procedure, 2,2-dichlorocyclobutanones are readily ...
