Syntheses of 4- and 5-chloro-cis-1,3-dimethylindanes

Reaction of chlorobenzene with crotonic acid under Friedel-Crafts conditions gives an unexpectedly high proportion of 4-chloro-3-methylindan-1-one together with the expected 6-chloro-3-methylindan-1-one. Hydrogenolysis of the tertiary alcohols which result from addition of methylmagnesium iodide to these compounds gives predominantly cis-4- and -5-chloro-1,3-dimethylindanes with only small amounts of the trans-isomers.