Application of the Suzuki reaction to the asymmetric desymmetrisation of 1,2- and 1,3-disubstituted bulky cobalt metallocenes

Reaction of (η5-cyclopentadienyl)(η4-tetraphenylcyclobutadiene)cobalt with Hg(OAc)2 (2.3 equiv) in 1:1 MeOH/CH2Cl2 followed by the addition of LiCl resulted in the formation of (η5-1,2-dichloromercuricyclopentadienyl)(η4-tetraphenylcyclobutadiene)cobalt (33%) and its 1,3-isomer (6%). Following conversion into their corresponding diiodides these compounds were desymmetrised by Suzuki reactions with ArB(OH)2 employing [(R)-BINAP]PdCl2, with the highest ee of 24% being obtained for (η5-1-iodo-3-(2-methoxyphenyl)cyclopentadienyl)(η4-tetraphenylcyclobutadiene)cobalt.

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