Diastereoselective [Cu(MeCN)4BF4/BF3·Et2O]-Catalyzed Cyclopropenation of Alkynes: Asymmetric Synthesis of β-Amino-α-cyclopropenyl PhosphonatesWe thank the Committee of Science and Technology of Tianjin (15JCYBJC20700), the Tianjin Rural Work Committee (201604020) and State Key Laboratory of Elemento-Organic Chemistry in Nankai University for financial support.
Received: 31 May 2017
Accepted after revision: 06 July 2017
03 August 2017 (online)
The diastereospecific formation of β-amino-α-cyclopropenyl phosphonates has been achieved in moderate yields from the cyclopropenation of 1-alkynes with dialkyl α-diazophosphonates. The reaction was performed by using a combined catalyst consisting of Cu(MeCN)4BF4 and BF3·Et2O as additive in dichloromethane at 40 °C. A possible mechanism for the reaction has been proposed to explain the origin of the activation and the asymmetric induction. This method provides a versatile approach to β-amino-α-cyclopropenylphosphonates containing a quaternary stereogenic center with good efficiency and diastereoselectivity.