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Paper | Special issue | Vol 74, No. 1, 2007, pp.637-648
Published online, 4th October, 2007
DOI: 10.3987/COM-07-S(W)44
An Alternative Chiral Synthesis of Wieland-Miescher Ketone Mediated by (S)-2-(Pyrrolidinylmethyl)pyrrolidine: Remarkable Effects of Brønsted Acid

Yuichi Akahane, Naoko Inage, Takashi Nagamine, Kohei Inomata,* and Yasuyuki Endo

*Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan

Abstract

The enantioselectivity of the intramolecular asymmetric aldol reaction mediated by (S)-2-(pyrrolidinylmethyl)pyrrolidine to prepare Wieland- Miescher ketone was examined in detail. A remarkable inversion of enantioselectivity was observed when a Brønsted acid was used as a co-catalyst. Development of the reaction to Robinson annulation was successfully achieved by the use of (S)-2-(pyrrolidinylmethyl)pyrrolidine as a Brønsted base, followed by trifluoroacetic acid as a Brønsted acid.