Abstract
Treatment of allylic dimethyl ethylenetricarboxylates (1,5) with ferric chloride gives high yields of 0-chloroalkyl 7-lactones (4,6) with stereospecific trans addition of carbon and chlorine to the double bond. With the cyclohexenyl
triester 13, only one of eight possible diastereomers is formed. Trimethyl ethylenetricarboxylate (24) adds to alkenes in the presence of ferric chloride in a cis fashion to give -lactones 26,28,30, and 32, arising from zwitterion formation followed by rapid attack of the carbonyl oxygen on the cation.