Visible-Light Organophotoredox-Mediated [3 + 2] Cycloaddition of Arylcyclopropylamine with Structurally Diverse Olefins for the Construction of Cyclopentylamines and Spiro[4.n] Skeletons

Abstract

We developed a visible-light-mediated [3 + 2] cycloaddition of arylcyclopropylamine with structurally diverse olefins using QXPT-NPh as a highly efficient organic photoredox catalyst. We first achieved the use of various alkyl-substituted alkenes in intermolecular [3 + 2] cycloadditions with cyclopropylamine. We also developed a general and efficient strategy for the construction of structurally diverse cyclopentane-based spiro[4.n] skeletons with 1,3-difunctional groups, which broadly exist in natural products and synthetic molecules. Furthermore, we proposed a hydrogen-bond mode between the arylcyclopropylamine and the photocatalyst QXPT-NPh.

Visible-light organophotoredox-mediated intermolecular formal [4 + 2] cycloadditions of arylcyclobutylamines with olefins

“…Therefore, we continued to test other photocatalysts. Many photocatalysts including the organic ones developed in our laboratory 14,15 have been tested (see the ESI for details †) and we found that most of the photocatalysts could promote the reaction and QXPT-NPhCN…”

“…This experiment shows that the N–H of 1a is essential, which is similar to our previous report on arylcyclopropylamines. 14 Stern–Volmer quenching studies showed that 1a quenched the visible-light-excited QXPT-NPhCN . However, both olefins 2a and 4p hardly quenched QXPT-NPhCN .…”

“…Therefore, we continued to test other photocatalysts. Many photocatalysts including the organic ones developed in our laboratory 14,15 have been tested (see the ESI for details†) and we found that most of the photocatalysts could promote the reaction and QXPT-NPhCN [ λ max, abs = 414 nm, E 1/2 (P/P−) = −1.63 V, E 1/2 (P * /P−) = +0.85 V, E 1/2 (P+/P) = +1.23 V and E 1/2 (P+/P * ) = −1.25 V vs. SCE in MeCN] was the best choice (entry 3). The addition of K 3 PO 4 increased the yield of 3a from 43% (entry 12) to 64% (entry 3).…”

“…To our delight, spiro-cycloadducts ( 5t–5w ) were successfully obtained in moderate yields and with excellent diastereoselectivities. However, unlike in the [3 + 2] cycloadditions of arylcyclopropylamines, 14 the scope of the olefins in [4 + 2] cycloadditions of arylcyclobutylamines is somewhat limited in which the alkyl olefins and electron-rich olefins did not afford the desired cycloadducts (see the ESI for details†). NMR experiments and X-ray crystallography analysis of 5p and 5w confirmed their stereochemistries (see the ESI for details†).…”

“…13 We have recently reported visible light-mediated [3 + 2] cycloaddition of arylcyclopropylamine with structurally diverse olefins using a highly efficient organic photocatalyst. 14 Herein, we report visible-light organophotoredox-mediated [4 + 2] cycloadditions of arylcyclobutylamines with olefins to afford 2-functionalized cyclohexylamines (Scheme 1).…”