o-nitrostyrene first reacts with triethyl phosphite, and the nitro group is converted to a nitroso group. The nitroso group then reacts with the alkene, and N-hydroxylindole is formed, which reacts again with triethyl phosphite to form the indole.[1][2][3][4]
Application
The CadoganâSundberg indole synthesis has been used as an intermediate step in the total synthesis of Tjipanazole E,[8] transforming 2-[trans-2-[5-Chloro-2-nitrophenyl)vinyl]-5-chloro-1H-indole to 5,5â-Dichloro-2,2â-biindole.
^
abSundberg, Richard J.; Yamazaki, Toshio (1 February 1967). "Rearrangements and ring expansions during the deoxygenation of ÎČ,ÎČ-disubstituted o-nitrostyrenes". The Journal of Organic Chemistry. 32 (2): 290â294.
doi:
10.1021/jo01288a009.
^
abSundberg, Richard J. (1 November 1965). "Deoxygenation of Nitro Groups by Trivalent Phosphorus. Indoles from o-Nitrostyrenes". The Journal of Organic Chemistry. 30 (11): 3604â3610.
doi:
10.1021/jo01022a006.
^Gribble, Gordon W. (17 June 2016). "CadoganâSundberg Indole Synthesis". Indole Ring Synthesis: From Natural Products to Drug Discovery. pp. 266â277.
doi:
10.1002/9781118695692.ch26.
ISBN9781118695692.
^Majgier-Baranowska, Helena; Williams, John D.; Li, Bing; Peet, Norton P. (1 February 1967). "Studies on the mechanism of the CadoganâSundberg indole synthesis". Tetrahedron Letters. 53 (35): 4785â4788.
doi:
10.1016/j.tetlet.2012.06.146.
^Li, Jie Jack (4 January 2014). "CadoganâSundberg indole synthesis". Indole Ring Synthesis: From Natural Products to Drug Discovery. Springer. p. 102-103.
doi:
10.1007/978-3-319-03979-4_49.
ISBN978-3-319-03979-4.
^Kuethe, Jeffrey T.; Wong, Audrey; Davies, Iaan W. (3 September 2003). "Effective Strategy for the Preparation of Indolocarbazole Aglycons and Glycosides: Total Synthesis of Tjipanazoles B, D, E, and I". Organic Letters. 5 (20): 3721â3723.
doi:
10.1021/ol035418r.
PMID14507214.