N-Heterocyclic Carbene Catalyzed Switchable Reactions of Enals with Azoalkenes: Formal [4 + 3] and [4 + 1] Annulations for the Synthesis of 1,2-Diazepines and Pyrazoles
作者:Chang Guo、Basudev Sahoo、Constantin G. Daniliuc、Frank Glorius
DOI:10.1021/ja510737n
日期:2014.12.17
A regio- and enantioselective formal [4 + 3] annulation reaction between enals and in situ formed azoalkenes has been achieved. A diverse set of 1,2-diazepine derivatives were synthesized in good yields with excellent enantioselectivities (often 99% ee). Alternatively, modifying the standard NHC catalyst switched the reactivity toward a formal [4 + 1] annulation to afford functionalized pyrazoles. The
Efficient Access to Chiral Trisubstituted Aziridines via Catalytic Enantioselective Aza-Darzens Reactions
作者:Barry M. Trost、Tanguy Saget、Chao-I Joey Hung
DOI:10.1002/anie.201607845
日期:2017.2.20
Herein, we report a Zn‐ProPhenol catalyzed aza‐Darzens reaction using chlorinated aromatic ketones as nucleophilic partners for the efficient and enantioselective construction of complex trisubstituted aziridines. The α‐chloro‐β‐aminoketone intermediates featuring a chlorinated tetrasubstituted stereocenter can be isolated in high yields and selectivities for further derivatization. Alternatively,