1. Lehrstuhl für Organische Chemie I, Technische Universität München, Lichtenbergstr. 4, D-85747 Garching, Germany
2. Universität Münster, Organisch-Chemisches Institut, Corrensstr. 40, D-48149 Münster, Germany

Correspondence to: Thorsten Bach¹ Correspondence and requests for materials should be addressed to T.B. (Email: thorsten.bach@ch.tum.de).

Abstract

Photoinduced electron transfer is an essential step in the conversion of solar energy into chemical energy in photosystems I and II (ref. 1), and is also frequently used by chemists to build complex molecules from simple precursors². During this process, light absorption generates molecules in excited electronic states that are susceptible to accepting or donating electrons. But although the excited states are straightforward to generate, their short lifetimes makes it challenging to control electron transfer and subsequent product formation—particularly if enantiopure products are desired. Control strategies developed so far use hydrogen bonding, to embed photochemical substrates in chiral environments³ and to render photochemical reactions enantioselective through the use of rigid chiral complexing agents⁴. To go beyond such stoichiometric chiral information transmission, catalytic turnover is required⁵. Here we present a catalytic photoinduced electron transfer reaction that proceeds with considerable turnover and high enantioselectivity. By using an electron accepting chiral organocatalyst that enforces a chiral environment on the substrate through hydrogen bonding, we obtain the product in significant enantiomeric excess (up to 70%) and in yields reaching 64%. This performance suggests that photochemical routes to chiral compounds may find use in general asymmetric synthesis.

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