Titanium-Catalyzed Diastereoselective Keto- and Iminonitrile Cyclizations
Christoph Kern1,2, Ritu Singh1, Michael A Unkrig-Bau2
1Department of Chemistry for Life Sciences, Uppsala University, Uppsala, Sweden.
None:
Substituted five-membered carbocycles with multiple stereocenters are common structural motifs of natural products but difficult to synthesize in a stereoselective fashion. In this study, we report a titanium(III)-catalyzed diastereoselective cyclization of keto- and iminonitriles that forms oxygenated and aminated cyclopentanones in good yield and diastereoselectivity. The derivatization into cyclopentyls with three consecutive stereocenters and a cyclopentenone is demonstrated. With support by DFT calculations, a transition state model is derived that is in agreement with an earlier proposal for related ketomalononitrile cyclizations.
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