Amino Acid-Derived Enaminones: A Study in Ring Formation Providing Valuable Asymmetric Synthons
15 Jun 2006-Journal of the American Chemical Society (American Chemical Society)-Vol. 128, Iss: 27, pp 8702-8703
TL;DR: Although disguised as a 6-endo-dig cyclization, the reagents employed in the transformation play a direct role in bond making and bond breaking, thus changing the mode of addition.
Abstract: A new reaction for the preparation of enaminones has been discovered. This method employs β-amino acids as starting materials to allow diversification as well as incorporation of chirality. The β-amino acids, once converted to ynones, are readily cyclized to the desired six-membered enaminone via a two-step, one-pot protocol. Although disguised as a 6-endo-dig cyclization, the reagents employed in the transformation play a direct role in bond making and bond breaking, thus changing the mode of addition.
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References
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TL;DR: A number of polyfunctional molecules have been examined as substrates for the 5-Endo-Trigonal ring-forming reaction, and it has been found that for first-row elements this is a disfavoured process, alternative reactions of type 5-Exo-trig generally taking precedence.
Abstract: A number of polyfunctional molecules have been examined as substrates for the 5-Endo-Trigonal ring-forming reaction, and it has been found that for first-row elements this is a disfavoured process, alternative reactions of type 5-Exo-Trig generally taking precedence; one case of a 5-Endo-Trig closure for a second-row element, sulphur, has been found.
324 citations
TL;DR: In this article, an overview of the chemistry of enaminones and related compounds containing the structural unit N-CaC-Z (Za COR, CO2R, CN, NO2, S O 2Ar, etc.).
Abstract: Efforts in our laboratories to devise a general approach to the synthesis of alkaloids focus on the versatile reactivity of enaminones and related compounds containing the structural unit N-CaC-Z (Za COR, CO2R, CN, NO2 ,S O 2Ar, etc.). This lecture presents an overview of our research with these useful building blocks. Themes to be elaborated include chemo- selectivity and diastereoselectivity in reactions of enaminones, and the challenge of controlling absolute stereochemistry.
130 citations
TL;DR: In this paper, nucleophilic addition of organometallics to chiral 1-acylpyridinium salts occurs with high diastereoselectivity to give N-acyl-2,3-dihydro-4-pyridones, which are useful building blocks for the asymmemc synthesis of various alkaloids.
83 citations
TL;DR: Stereoselective vinylcupration of a cyclopropenone acetal, followed by in situ electrophilic trapping with an alkylating agent, affords a cis-substituted vinylcyclopropane 2, witch stereoselectively rearranges to the acetal of a cross-conjugate dienone 3 upon thermolysis at 60-160 o C
Abstract: Stereoselective vinylcupration of a cyclopropenone acetal (1), followed by in situ electrophilic trapping with an alkylating agent, affords a cis-substituted vinylcyclopropane 2, witch stereoselectively rearranges to the acetal of a cross-conjugate dienone 3 upon thermolysis at 60-160 o C
22 citations