Ketones transmetallation, diethylzinc

A transmetallation to titanium derivatives - also promotes the addition of various zinc organo-metallics to carbonyl cmnpounds. However, the functional group tolerance seems to be limited (see Scheme lO), - - Interestingly, diethylzinc reacts with aromatic 1,2-diketones to give a-ethoxy ketones (see equation 10). ... 

Scheme 7.50 Transmetallation of phenylboronic acid with diethylzinc and enantioselective addition to ketones, as described by Yus and coworkers [80].

The chiral 6is-(sulfonamide) 510 catalyzes the enantioselective addition of boronic acids to aromatic ketones in the presence of diethylzinc. Actually, this reaction proceeds via the transmetalation of a boronic acid giving the corresponding organozinc intermediate. The reaction produces interesting tertiary diaryIcarbinols such as 511 in up to 93% ee (Scheme 2-147, eq. Rudolph et al. have shown that this approach can... 

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