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[摘要]：Dirhodium(II) caprolactamate exhibits optimal efficiency for the prodn. of the tert-butylperoxy radical, which is a selective reagent for hydrogen atom abstraction. These oxidn. reactions occur with aq. tert-Bu hydroperoxide (TBHP) without rapid hydrolysis of the caprolactamate ligands on dirhodium. Allylic oxidns. of enones yield the corresponding enedione in moderate to high yields, and applications include allylic oxidns. of steroidal enones. Although methylene oxidn. to a ketone is more effective, Me oxidn. to a carboxylic acid can also be achieved. The superior efficiency of dirhodium(II) caprolactamate as a catalyst for allylic oxidns. by TBHP (mol % of catalyst, % conversion) is described in comparative studies with other metal catalysts that are also reported to be effective for allylic oxidns. That different catalysts produce essentially the same mixt. of products with the same relative yields suggests that the catalyst is not involved in product-forming steps. Mechanistic implications arising from studies of allylic oxidn. with enones provide new insights into factors that control product formation. A previously undisclosed disproportionation pathway, catalyzed by the tert-butoxy radical, of mixed peroxides for the formation of ketone products via allylic oxidn. has been uncovered. |
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