The transition metal-catalyzed asymmetric cyclopropylphosphonation of olefins with diazomethylphosphonates is a highly useful synthetic transformation for the construction of optically active cyclopropylphosphonate frameworks, which play an important role in natural product and unnatural analogues of pharmaceutical chemistry. Because of the high potential of cyclopropylphosphonation in asymmetric synthesis, while there are only a few applications of alkene cyclopropanation of substrates other than styrene derivatives, we envisioned that developing different substrates from olefins in enantioenriched form would be of considerable value. Recently, we reported that the complex, Ru(II)-Pheox, is extremely efficient in the asymmetric cyclopropanation of diazomethylphosphonates with electron-rich or electron-deficient olefins. In continuation of our research interest in the chemistry of carbene transfer reaction, we discovered a novel direct catalytic asymmetric cyclopropanation via the C–H activation of diazomethylphosphonates with N-ethylaniline derivatives. Herein, we describe the first catalytic asymmetric cyclopropanation via the C–H activation reaction of diazomethylphosphonates with N-ethylaniline derivatives in good yield and excellent enantioselectivity (up to 49% yield, 99% ee) without detecting of any trace of cis-isomer by using the Ru(II)-Pheox complex. Although the yields were moderate in most cases, to the best of our knowledge, this is the first example of direct asymmetric cyclopropanations by using alkyl groups instead of alkenyl groups as the substrates. Furthermore, C–H insertion reaction on methyl group of N,N-dimethylaniline and diazomethylphosphonate also exposed as a premise to discover the new cyclopropylphosphonate reaction above, its product can give the corresponding β-aminophosphonate up to an outstanding yield of 72%.

Direct Ru(II)-pheox catalyzed asymmetric cyclopropanation of diazomethylphosphonates with N-ethylaniline derivatives

255th National Meeting (2018)

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