Transition metals of the fourth row are abundant and cheap compared to those of the fifth and sixth rows.Therefore,by introducing new reactivities with fourth-row metal complexes,it might be possible to replace fifth- and sixth-row metals in some of the more fundamental and important reactions.Catalytic Grignard-type addition of nucleophiles to aldehydes is one such reaction.Grignard reagents are usually prepared from organic halides and magnesium metal,but this procedure results in the undesired formation of stoichiometric amounts of metal salts.One way to solve this problem is to generate the nucleophiles by C-H bond activation;however,it has been difficult to promote nucleophilic addition after the C-H activation step.We report herein that 1) a complexe of manganese,a fourth-row transition metal,can be employed for C-H bond activation of aromatic compounds;2) catalytic insertion of aldehydes into the C-H bond is achieved with the manganese complex by the addition of Et3SiH.
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