Rhodium(I)-catalyzed synthesis of indoles: amino-Claisen rearrangement of N-propargylanilines.
Mild and facile preparations of 2-substituted or 2,3-disubstituted indole compounds were achieved by RhH(CO)(Ph(3)P)(3) (4-10 mol %)-catalyzed reaction of N-propargylanilines in hexafluoroisopropyl alcohol (HFIP). The formation of indoles was proven to be derived from an o-allenylaniline intermediate, which was generated by the Rh(I)-catalyzed amino-Claisen rearrangement of N-propargylanilines. The catalytic system is also available for the one-pot synthesis of indoles by reacting N-alkylaniline (1 equiv) with propargyl bromide (1.3 equiv) in the presence of K(2)CO(3) (3 equiv) in HFIP. The active catalyst was proven to be [Rh(CO)(Ph(3)P)(2)]OCH(CF(3))(2) generated in situ from RhH(CO)(Ph(3)P)(3) and HFIP. The structure of [Rh(CO)(Ph(3)P)(2)]OCH(CF(3))(2) was confirmed by single-crystal X-ray crystallographic analysis.
Saito
Akio
A
Laboratory of Organic Reaction Chemistry, Showa Pharmaceutical University, 3-3165 Higashi-Tamagawagakuen, Machida, Tokyo 194-8543, Japan. akio-sai@ac.shoyaku.ac.jp
Oda
Shoko
S
Fukaya
Haruhiko
H
Hanzawa
Yuji
Y
D000814:Aniline Compounds / Q000737:chemistry*; D001965:Bromides / Q000737:chemistry; D002384:Catalysis; D018360:Crystallography, X-Ray; D007211:Indoles / Q000138:chemical synthesis* / Q000737:chemistry; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D020005:Propanols / Q000737:chemistry; D012238:Rhodium / Q000737:chemistry*; D006845:Hydrocarbons, Fluorinated
D000814:Aniline Compounds; D001965:Bromides; D007211:Indoles; D009942:Organometallic Compounds; D020005:Propanols; D012238:Rhodium; C001337:hexafluoroisopropanol; D006845:Hydrocarbons, Fluorinated; C023650:aniline