Synthesis of 4-, 5-, 11-, and 12-(Chloromethyl)benzopyrene

Article abstract of DOI:10.1021/jo00205a002

The previously unknown title compounds have been synthesized in excellent yields from the ethyl arylacetates 3a-d.Formylation of 3a-d allowed the isolation of formyl esters 4a-d that were cyclized by a novel procedure utilizing dilute solutions (5-10percent) of methanesulfonic acid in methylene chloride.The resulting benzopyrene ethyl esters were transformed to the target chloromethyl compound by reduction (LAH) followed by reaction with thionyl chloride.The overall yields obtained from esters 3a-d ranged from 44percent to 66percent.These compounds can be used as immediate precursors of benzopyrenylmethyl carbocations which are believed to be relevant in certain carcinogenesis mechanisms.