Carbocations as Lewis Acid Catalysts in Diels-Alder and Michael Addition Reactions
作者:Juho Bah、Johan Franzén
DOI:10.1002/chem.201304160
日期:2014.1.20
the carbocation as a highly powerful Lewis acid catalyst for organic reactions. The stable and easily available triphenylmethyl (trityl) cation was found to be a highly efficient catalyst for the Diels–Alder reaction for a range of substrates. Catalyst loadings as low as 500 ppm, excellent yields, and good endo/exo selectivities were achieved. Furthermore, by changing the electronic properties of the
Recyclable organotungsten Lewis acid and microwave assisted Diels–Alder reactions in water and in ionic liquids
作者:I-Hon Chen、Jun-Nan Young、Shuchun Joyce Yu
DOI:10.1016/j.tet.2004.09.078
日期:2004.12
water-soluble, organotungsten Lewisacid, [OP(2-py)3W(CO)(NO)2](BF4)2 (1), was synthesized and characterized. A series of 1-catalyzed Diels–Alderreactions were investigated under conventional heating or microwave heating conditions. The cycloaddition reactions were efficiently conducted in either water or in an ionicliquid, 1-butyl-3-methylimidazolium hexafluorophosphate. The ionicliquid acts as a powerful
作者:Thiemo Arndt、Philip K. Wagner、Jonas J. Koenig、Martin Breugst
DOI:10.1002/cctc.202100342
日期:2021.6.18
The Diels-Alder cycloaddition is the most popular pericyclic reaction with numerous applications in synthesis and catalysis. We now demonstrate that we can perform this reaction under mild and metal-free conditions relying on molecular iodine as the catalyst. Cycloadditions with cyclohexadiene, cyclopentadiene, or isoprene with various dienophiles can be performed typically within minutes in moderate
The development of a new method for effecting [4+2] cycloadditions on the surface of chromatographic adsorbents in the absence of solvents that leads to a moderation of the reaction conditions and an increase in selectivity is described.
Taming the Silylium Ion for Low-Temperature Diels-Alder Reactions
作者:Hendrik F. T. Klare、Klaus Bergander、Martin Oestreich
DOI:10.1002/anie.200904520
日期:2009.11.16
trivalent silicon cation stabilized by an electron‐rich transition metal as the “hot” Lewis acidic site catalyzes challenging Diels–Alderreactions at low temperatures with excellent reaction rates and selectivities (see scheme). In addition to the chemical stability of the silyliumion catalyst (in CH2Cl2), the potential of these reactive compounds is also discussed.