142977-31-9Relevant academic research and scientific papers
Formal homo-nazarov and other cyclization reactions of activated cyclopropanes
De Simone, Filippo,Saget, Tanguy,Benfatti, Fides,Almeida, Sofia,Waser, Jerome
, p. 14527 - 14538 (2012/02/04)
The Nazarov cyclization of divinyl ketones gives access to cyclopentenones. Replacing one of the vinyl groups by a cyclopropane leads to a formal homo-Nazarov process for the synthesis of cyclohexenones. In contrast to the Nazarov reaction, the cyclization of vinyl-cyclopropyl ketones is a stepwise process, often requiring harsh conditions. Herein, we describe two different approaches for further polarization of the three-membered ring of vinyl-cyclopropyl ketones to allow the formal homo-Nazarov reaction under mild catalytic conditions. In the first approach, the introduction of an ester group α to the carbonyl on the cyclopropane gave a more than tenfold increase in reaction rate, allowing us to extend the scope of the reaction to non-electron-rich aryl donor substituents in the β position to the carbonyl on the cyclopropane. In this case, a proof of principle for asymmetric induction could be achieved using chiral Lewis acid catalysts. In the second approach, heteroatoms, especially nitrogen, were introduced β to the carbonyl on the cyclopropane. In this case, the reaction was especially successful when the vinyl group was replaced by an indole heterocycle. With a free indole, the formal homo-Nazarov cyclization on the C3 position of indole was observed using a copper catalyst. In contrast, a new cyclization reaction on the N1 position was observed with BrAnsted acid catalysts. Both reactions were applied to the synthesis of natural alkaloids. Preliminary investigations on the rationalization of the observed regioselectivity are also reported.
Synthetic studies on the key component of the new generation of quinolonecarboxylic acid, DU-6859. 1. Synthesis of (1R,2S)-2-fluorocyclopropylamine by the use of optical resolution
Tamura, Osamu,Hashimoto, Masaru,Kobayashi, Yuko,Katoh, Tadashi,Nakatani, Kazuhiko,Kamada, Masahiro,Hayakawa, Isao,Akiba, Toshifumi,Terashima, Shiro
, p. 3889 - 3904 (2007/10/02)
The title synthesis was achieved by employing highly cis-selective cyclopropanation of N-benzyl-N-vinylcarbamates with zinc-monofluorocarbenoid, deprotection of the formed N-benzyl-N-(cis-2-fluorocyclopropyl)carbamates, and optical resolution of the resul
Synthesis and optical resolution of dl-cis-2-fluorocyclopropylamine, the key component of the new generation of quinolonecarboxylic acid, DU-6859
Tamura,Hashimoto,Kobayashi,Katoh,Nakatani,Kamada,Hayakawa,Akiba,Terashima
, p. 3483 - 3486 (2007/10/02)
The title synthesis was accomplished by featuring highly cis-selective cyclopropanation of an N-vinylcarbamate with zinc-monofluorocarbenoid followed by deprotection of the formed N-(cis-2-fluorocyclopropyl)carbamate. Optical resolution of dl-cis-2-fluoro
