borate ion comprising an O,N,N,O‐tetradentate backbone, which ensures hitherto unattainable structural robustness. Upon pairing with a proton, the hydrogen borate acts as an effective catalyst for the asymmetric Prins‐type cyclization of vinyl ethers, providing access to structurally and stereochemically defined dihydropyrans. The key to selectivity control is the distinct ability of the borate ion to
Catalytic Ring Expansion of Vinyl Oxetanes: Asymmetric Synthesis of Dihydropyrans Using Chiral Counterion Catalysis
作者:Boying Guo、Gregg Schwarzwalder、Jon T. Njardarson
DOI:10.1002/anie.201201367
日期:2012.6.4
Acid Showdown! The first catalyticring expansion of vinyl oxetanes to 3,6‐dihydro‐2H‐pyrans is described. Copper(II) triflate emerged as the best catalyst for this new transformation, which has broad scope as demonstrated by the eighteen examples included. The symmetric vinyl oxetane substrate can be asymmetrically desymmetrized when using either chiral Lewis or Brønsted acids as catalysts.
Cationic iron(III) porphyrin was found to be an efficient catalyst for the highly chemoselective hetero-Diels Alder-type reaction of aldehydes with 1,3-dienes. The catalyzed process did not require the use of electron-deficient aldehydes such as glyoxylic acid derivatives or activated electron-rich 1,3-dienes such as Danishefslcy's diene and Rawal's diene. The high functional group tolerance and robustness of the catalyst were demonstrated. Further, the potential utility of the catalyst was demonstrated by performing the cycloaddition in the presence of water and by carrying out cycloaddition of an unactivated ketone such as cyclohexanone with a diene.
Romanov, N. A.; Kantor, E. A.; Musavirov, R. S., Journal of Organic Chemistry USSR (English Translation), 1981, vol. 17, p. 1576 - 1581
作者:Romanov, N. A.、Kantor, E. A.、Musavirov, R. S.、Karakhanov, R. A.、Rakhmankulov, D. L.
DOI:——
日期:——
Romanov, N. A.; Kantor, E. A.; Karakhanov, R. A., Journal of Organic Chemistry USSR (English Translation), 1982, vol. 18, # 2, p. 351 - 354
作者:Romanov, N. A.、Kantor, E. A.、Karakhanov, R. A.、Rakhmankulov, D. L.