Iridium-Catalyzed Enantioselective Cyclopropenation
M. Uehara, H. Suematsu, Y. Yasutomi, T. Katsuki*
Kyushu University, Fukuoka, Japan
16. Februar 2011 (online)
Significant effort has been made to prepare substituted cyclopropenes in an enantiomerically pure fashion since they are useful building blocks, which can be further modified in numerous ways. The methodology described herein utilizes chiral iridium(salen) complexes of type 4 and 5 to achieve the enantioselective cyclopropenation of terminal alkynes 2 using different diazo compounds of type 1 as carbenoid precursors. The cyclopropenation towards the target compounds 3 could be achieved with good to excellent yields and high enantioselectivities.