A catalyst-free 1,3-dipolar cycloaddition of C,N-cyclic azomethine imines and 3-nitroindoles: an easy access to five-ring-fused tetrahydroisoquinolines

A catalyst-free 1,3-dipolar cycloaddition of C,N-cyclic azomethine imines and 3-nitroindoles: an easy access to five-ring-fused tetrahydroisoquinolines

Green Chem., 2016, Advance Article

DOI: 10.1039/C6GC02517J, Communication

Xihong Liu, Dongxu Yang, Kezhou Wang, Jinlong Zhang, Rui Wang

A catalyst-free 1,3-dipolar cycloaddition of C,N-cyclic azomethine imines and 3-nitroindoles has been reported under mild conditions.

A catalyst-free 1,3-dipolar cycloaddition of C,N-cyclic azomethine imines and 3-nitroindoles: an easy access to five-ring-fused tetrahydroisoquinolines

Xihong Liu,a   Dongxu Yang,a   Kezhou Wang,a  Jinlong Zhanga and   Rui Wang*ab  

*Corresponding authors

aSchool of Life Sciences, Institute of Biochemistry and Molecular Biology, Lanzhou University, Lanzhou 730000, P. R. China

bState Key Laboratory of Chiroscience, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Kowloon, P. R. China

Green Chem., 2016, Advance Article

DOI: 10.1039/C6GC02517J

We have reported herein a catalyst-free 1,3-dipolar cycloaddition of C,N-cyclic azomethine imines and 3-nitroindoles by which a series of five-ring-fused tetrahydroisoquinolines featuring an indoline scaffold were obtained as single diastereomers in moderate to high yields without any additives under mild conditions. Moreover, the current method provides a novel and convenient approach for the efficient incorporation of two biologically important scaffolds (tetrahydroisoquinoline and indoline).

ethyl 13b-nitro-8-tosyl-8,8a,13b,13c-tetrahydro-5H-indolo[2′,3′:3,4]pyrazolo[5,1- a]isoquinoline-9(6H)-carboxylate

ethyl 13b-nitro-8-tosyl-8,8a,13b,13c-tetrahydro-5H-indolo[2′,3′:3,4]pyrazolo[5,1- a]isoquinoline-9(6H)-carboxylate:

White solid, m.p. 153 – 154 oC; 94% yield; 1H NMR (300 MHz, CDCl3) δ 7.86 (d, J = 8.2 Hz, 2H), 7.78 (d, J = 7.9 Hz, 1H), 7.30 – 7.13 (m, 5H), 7.1 (s, 1H), 7.05 – 6.94 (m, 1H), 6.94 – 6.87 (m, 1H), 6.59 (t, J = 7.6 Hz, 3H), 6.28 (d, J = 7.6 Hz, 1H), 4.78 (s, 1H), 4.37 (q, J = 7.1 Hz, 2H), 2.80 – 2.58 (m, 2H), 2.33 (s, 3H), 2.31 – 2.11 (m, 2H), 1.41 (t, J = 7.1 Hz, 3H) ppm;

13C NMR (75 MHz, CDCl3) δ 152.1, 144.6, 142.6, 134.0, 132.1, 129.3, 129.0, 128.7, 128.3, 127.5, 127.3, 126.2, 122.8, 121.1, 115.5, 104.5, 84.9, 70.7, 62.8, 48.5, 29.1, 21. 6, 14.3 ppm;

HRMS (ESI): C27H26N4NaO6S [M + Na]+ calcd: 557.1465, found: 557.1476.

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