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Light-driven deracemization enabled by excited-state electron transfer.


ABSTRACT: Deracemization is an attractive strategy for asymmetric synthesis, but intrinsic energetic challenges have limited its development. Here, we report a deracemization method in which amine derivatives undergo spontaneous optical enrichment upon exposure to visible light in the presence of three distinct molecular catalysts. Initiated by an excited-state iridium chromophore, this reaction proceeds through a sequence of favorable electron, proton, and hydrogen-atom transfer steps that serve to break and reform a stereogenic C-H bond. The enantioselectivity in these reactions is jointly determined by two independent stereoselective steps that occur in sequence within the catalytic cycle, giving rise to a composite selectivity that is higher than that of either step individually. These reactions represent a distinct approach to creating out-of-equilibrium product distributions between substrate enantiomers using excited-state redox events.

SUBMITTER: Shin NY 

PROVIDER: S-EPMC6939311 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Light<b>-</b>driven deracemization enabled by excited<b>-</b>state electron transfer.

Shin Nick Y NY   Ryss Jonathan M JM   Zhang Xin X   Miller Scott J SJ   Knowles Robert R RR  

Science (New York, N.Y.) 20191001 6463


Deracemization is an attractive strategy for asymmetric synthesis, but intrinsic energetic challenges have limited its development. Here, we report a deracemization method in which amine derivatives undergo spontaneous optical enrichment upon exposure to visible light in the presence of three distinct molecular catalysts. Initiated by an excited-state iridium chromophore, this reaction proceeds through a sequence of favorable electron, proton, and hydrogen-atom transfer steps that serve to break  ...[more]

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