40015-13-2Relevant articles and documents
Synthesis of indoles from anilines and intermediates therein
-
, (2008/06/13)
Preparing indoles and intermediates therefor by reacting an N-haloaniline with a β-carbonylic hydrocarbon sulfide to form an azasulfonium halide, reacting the azasulfonium halide with a strong base to form a thio-ether indole derivative, and then reducing the thio-ether indole, e.g. with Raney nickel, to form the indole compound. When an acetal or ketal of the β-carbonyl hydrocarbon sulfide is used, the azasulfonium salt is treated with a base, and then with an acid to form the thio-ether indole derivative. When an α-ethyl-β -carbonylic hydrocarbon sulfide is used, the resulting azosulfonium salt reacts with strong base to form a thio-ether indolenine derivative, which on reduction with Raney nickel or complex metal hydrides yields 3-substituted indoles. The aniline may be an aminopyridine to form an aza-indole compound in the process. The azasulfonium salts and thio-ether indole or thio-ether indolenine derivatives can be isolated and recovered from their respective reaction mixtures. The thio-ether-indole and thio-ether indolenine derivatives are useful as intermediates to make the indoles without the thio-ether group. The indoles are known compounds having a wide variety of uses, e.g., in making perfumes, dyes, amino acids, pharmaceuticals, agricultural chemicals and the like.
