5 meso posit'ion since, as shown by Fieser and X e~ man,~ groups attached to the methyl group that is involved in ring closure are cleaved during the high-temperature reaction. A second method is based on the reaction of diberiz [a, h] ant hraquinone and an appropriate Grignard reagent followed by reduction of t'he resultant carbinol to the hydrocarbon. This method is limited to the preparation of derivatives with substituents in both of the ineso ...