ASYMMETRIC-SYNTHESIS OF (R)-(+)-ALPHA-METHYL-O-METHOXYBENZYL METHYL-ETHER VIA THE STEREOSELECTIVE BENZYLIC ELABORATION OF TRICARBONYL (ETA-6-O-METHOXYBENZYL METHYL ETHER)CHROMIUM(O)

Treatment of tricarbonyl(eta6-o-methoxybenzyl methyl ether)chromium(0) with t-butyllithium followed by an electrophile gives a single diastereoisomer of the corresponding alpha substituted complex. The relative configuration within the product from methylation, tricarbonyl(eta6-alpha-methyl-o-methoxybenzyl methyl ether)chromium(0), has been established via a single crystal X-ray structure analysis and found to be (RS,RS); the stereoselectivity thus arising from a non-chelation controlled mechanism. Repetition of the reaction on homochiral (+)-tricarbonyl(eta6-o-methoxybenzyl methyl ether)chromium(O) gives, after decomplexation, homochiral (R)-(+)-alpha-methyl-o-methoxybenzyl methyl ether.