Ir(salen) complexes were found to catalyze enantioselective cyclopropenation efficiently. Cyclopropenation can be carried out using either a donor/acceptor- or an acceptor/acceptor-substituted diazo compound such as α-aryl-α-diazoacetates, α-phenyl-α-diazophosphonate, 2,2,2-trifluoro-1-phenyl-1-diazoethane, and α-cyano-α-diazoacetamide as carbenoid precursors. The reactions provide highly enantioenriched cyclopropenes (84-98% ee) with a functionalized quaternary carbon as versatile building blocks.
Enantioenriched Synthesis of Cyclopropenes with a Quaternary Stereocenter, Versatile Building Blocks. -The first highly enantioselective pathway to chiral cyclopropenes that include a chiral quaternary carbon atom carrying cyano, phosphonate, trifluoromethyl, or amide groups shows great tolerances to a variety of functional groups. -(UEHARA, M.; SUEMATSU, H.; YASUTOMI, Y.; KATSUKI*, T.; J. Am. Chem. Soc. 133 (2011) 2, 170-171, http://dx.
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