Synfacts 2009(6): 0609-0609  
DOI: 10.1055/s-0029-1216708
Synthesis of Heterocycles
© Georg Thieme Verlag Stuttgart ˙ New York

Preparation of Substituted Indoxyls and Aminoindoles

Contributor(s): Victor Snieckus, Toni Rantanen
Jr., J. S. Schneekloth, J. Kim, E. J. Sorensen*
Princeton University, USA
Further Information

Publication History

Publication Date:
25 May 2009 (online)


Reported is a variation of the classical Ugi reaction, in which the nitrilium ion generated by the addition of the isocyanide to the iminium ion is interrupted by an electron-rich arene. The authors hypothesized such a trapping to proceed by replacing the carboxylic acid component with a Brønsted or a Lewis acid (J. A. Deyrup et al. Tetrahedron 1969, 25, 1467). Screening of a variety of acids led to triflic acid A as the reagent of choice. When R4 ∂ H, the imino intermediates may be ­hydrolyzed under mild conditions to afford substituted indoxyls. The substrate scope was fairly well studied and the reaction proceeds in yields ranging from moderate to excellent.