Enantiospecific Synthesis of 9,10-Dihalocamphors

A new, general and straightforward method for the enantiospecific synthesis of 9,10-dihalocamphors (including mixed derivatives) is reported and exemplified for the preparation of (+)-9,10-dibromocamphor (a well-known chiral intermediate) as well as (+)-9-bromo-10-chlorocamphor and (+)-9-bromo-10-iodocamphor (novel mixed dihalides). Our approach is based on a key stereocontrolled tandem electrophilic addition - Wagner-Meerwein rearrangement of optically pure 3-endo-(halomethyl)-3-methyl-2-methylenenorbornan-1-ols, which are easily obtained from readily accessible 9-halocamphors.