155156-95-9Relevant articles and documents
Iodine-Catalyzed Diels-Alder Reactions
Arndt, Thiemo,Wagner, Philip K.,Koenig, Jonas J.,Breugst, Martin
, p. 2922 - 2930 (2021/05/17)
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 to good yields and high endo selectivity. The mechanistic studies including kinetic and DFT investigations clearly indicate a halogen-bond activation and rule out other modes of activation. Furthermore, iodine performs equally well as typical metallic Lewis acids like AlCl3, SnCl4, or TiCl4.
Diazepane Carboxylates as Organocatalysts in the Diels–Alder Reaction of α-Substituted Enals
H?ggman, Nicklas O.,Zank, Benjamin,Jun, HyunJune,Kaldre, Dainis,Gleason, James L.
supporting information, p. 5412 - 5416 (2018/10/20)
Ethyl diazepane carboxylate efficiently catalyzes the Diels–Alder cycloaddition of α-substituted-α,β-unsaturated aldehydes via iminium ion organocatalysis. The reaction is applicable to a range of dienes and dienophiles and generally proceeds at room temperature in the presence of 5 mol-% catalyst and 2.5 mol-% triflic acid co-catalyst. The incorporation of a stereogenic center on the diazepane backbone in combination with a menthyl carbamate produces a catalyst which affords enantioselectivities of 70–95 % ee for the cycloaddition of cyclopentadiene with a range of dienophiles. The enantioselectivity is rationalized via a transition state in which electrostatic stabilization by the carboxylate directs the diene to the more hindered face of the dienophile.
Enantioselective Diels-Alder Reaction Induced by Chiral Supramolecular Lewis Acid Catalysts Based on CN?B and PO?B Coordination Bonds
Hatano, Manabu,Hayashi, Kazushi,Sakamoto, Tatsuhiro,Makino, Yuma,Ishihara, Kazuaki
, p. 1061 - 1067 (2016/05/19)
Chiral supramolecular boron Lewis acid catalysts were prepared from chiral 3-phosphoryl-1,1′-bi-2-naphthols, (2-cyanophenyl)boronic acids, and tris(pentafluorophenyl)borane, bound through CN···B and PO···B coordination bonds. In particular, the coordinated tris(pentafluorophenyl)boranes increase the Lewis acidity of the active center in the manner of a Lewis acid assisted Lewis acid catalyst system. A possible cavity in these catalysts was highly suitable for several Diels-Alder probe reactions of acroleins with cyclic or acyclic dienes, which gave the corresponding adducts in good to high yields and high enantio-selectivities.
