Tert-butylphenylketone

Ruthenium-catalyzed asymmetric reductions of aromatic ketones 180 can be performed under microwave irradiation. Moberg [98] described this reaction using a monomode microwave reactor and ruthenium complexes 182 with enan-tiomerically pure chiral diamines 181 (Scheme 5.51). The reaction is very fast and efficient even sterically hindered tert-butylphenylketone, which is normally quite umeactive, was reduced in almost quantitative yield in 3 minutes. The enantio-selectivity was, however, lower than that obtained under standard conditions similarly to that described by Larhed [77] in the enantioselective Heck reaction between cydopentene 115 and phenyl triflate 116 (Scheme 5.33). 

According to low temperature C-NMR study on the affinity of MAD with oxygen containing functional groups, such as carbonyl compounds and ethers, coordination of amides to MAD is stronger than that of aldehydes, ester, and ketones, while coordination of ethers is rather weak [46). One of the most important synthetic utilities of MAD is that in the hydride reduction of two different ketones MAD can protect the less hindered ketone or more basic ketones by forming complexes with these ketones, that is, selective reduction of more hindered free ketones can realize. As shown in Scheme 6.38, for example, DIBAL reduction (1 equivalent) of a 1 1 mixture of acetophenone and tert-butylphenylketone provide two carbinols with low chemoselectivity. On the other hand, in the presence of... 

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