Enantioselective organocatalysis using SOMO activation.

The asymmetric α-addition of relatively nonpolar hydrocarbon substrates, such as allyl and aryl groups, to aldehydes and ketones remains a largely unsolved problem in organic synthesis, despite the wide potential utility of direct routes to such products. We reasoned that well-established chiral amine catalysis, which activates aldehydes toward electrophile addition by enamine formation, could be expanded to this important reaction class by applying a single-electron oxidant to create a transient radical species from the enamine. We demonstrated the concept of singly occupied molecular orbital (SOMO) activation with a highly selective α-allylation of aldehydes, and we here present preliminary results for enantioselective heteroarylations and cyclization/halogenation cascades.

Rh(I)-catalyzed direct ortho-alkenylation of aromatic ketimines with alkynes and its application to the synthesis of isoquinoline derivatives.

[reaction: see text] Novel synthetic methods of both ortho-alkenylated aromatic ketones and isoquinoline derivatives have been developed through the Rh(I)-catalyzed direct ortho-alkenylation of common aromatic ketimines with alkynes. Furthermore, a highly efficient one-pot synthesis of isoquinoline derivatives was achieved by simply mixing aromatic ketone, benzylamine, and alkyne under a Rh(I) catalyst.

Chelation-assisted Rh(I)-catalyzed ortho-alkylation of aromatic ketimines or ketones with olefins.

Described herein is the Rh(I)-catalyzed ortho-alkylation of aromatic ketimines or ketones with olefins. This method showed high reactivity and selectivity to monoalkylation for a variety of olefins including 1-alkenes with an allylic proton, alpha,omega-dienes, and internal olefins. For a mechanistic study, H/D exchange experiments were carried out, which demonstrated that the ortho C-H bond could be easily cleaved even at the low temperature of 45 degrees C. The key step of this reaction is the formation of a stable five-membered metallacycle by a chelation-assisted ortho C-H bond activation. Furthermore, the direct ortho-alkylation of aromatic ketones with the Rh(I) complex was successfully achieved by adding 50 mol % of benzylamine as a chelation-assistant tool.