136577-69-0Relevant articles and documents
Remote Tris(pentafluorophenyl)borane-Assisted Chiral Phosphoric Acid Catalysts for the Enantioselective Diels-Alder Reaction
Hatano, Manabu,Ishihara, Hideyuki,Goto, Yuta,Ishihara, Kazuaki
, p. 564 - 570 (2016)
Tris(pentafluorophenyl)borane-assisted chiral supramolecular phosphoric acid catalysts were developed for the model Diels-Alder reaction of α-substituted acroleins with cyclopentadiene. Two remotely coordinated tris(pentafluorophenyl)boranes should help to increase the Bronsted acidity of the active center in the supramolecular catalyst and create effective bulkiness for the chiral cavity. The prepared supramolecular catalysts acted as not only conjugated Bronsted acid-Bronsted base catalysts but also bifunctional Lewis acid-Bronsted base catalysts with the addition of a central achiral Lewis acid source such as catecholborane.
Br?nsted acid assisted chiral lewis acid (BLA) catalyst for asymmetric Diels-Alder reaction
Ishihara, Kazuaki,Yamamoto, Hisashi
, p. 1561 - 1562 (1994)
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Arene-Ruthenium Complexes of 1,1′-Bis(ortho-carborane): Synthesis, Characterization, and Catalysis
Chan, Antony P. Y.,Jeans, Rebekah J.,Riley, Laura E.,Rosair, Georgina M.,Sivaev, Igor B.,Taylor, James,Welch, Alan J.
, (2019)
Deprotonation of 1,1′-bis(ortho-carborane) with nBuLi in THF followed by reaction with [RuCl2(p-cymene)]2 affords, in addition to the known compound [Ru(κ3-2,2′,3′-{1-(1′-closo-1′,2′-C2B10H10)-closo-1,2-C2B10H10)}(p-cymene)] (I), a small amount of a new species, [Ru(κ3-2,2′,11′-{1-(7′-nido-7′,8′-C2B9H11)-closo-1,2-C2B10H10)}(p-cymene)] (1a), with two B-agostic B-H?Ru bonds, making the bis(carborane) unit a closo-nido-X(C)L2 ligand, a previously unreported bonding mode. Similar species were also formed with arene = benzene (1b), mesitylene (1c), and hexamethylbenzene (1d), although in the last two cases the metallacarborane-carborane species [1-(1′-closo-1′,2′-C2B10H11)-3-(arene)-closo-3,1,2-RuC2B9H10)], 2c and 2d, were also isolated. With the bis(ortho-carborane) transfer reagent [Mg(κ2-2,2′-{1-(1′-closo-1′,2′-C2B10H10)-closo-1,2-C2B10H10)}(DME)2], the target compounds [Ru(κ3-2,2′,3′-{1-(1′-closo-1′,2′-C2B10H10)-closo-1,2-C2B10H10)}(arene)], 4b and 4d, were prepared in reasonable-to-good yields, although for arene = benzene and mesitylene small amounts of the unique paramagnetic species [{Ru(arene)}2(μ-Cl)(μ-κ4-2,2′,3,3′-{1-(1′-closo-1′,2′-C2B10H9)-closo-1,2-C2B10H9})], 3b and 3c, were also formed. In compounds 3, the bis(carborane) acts as a closo-closo-X4(C,C′,B,B′) ligand to the Ru2 unit. In I, 4b, and 4d, the B-agostic B-H?Ru bond is readily cleaved by MeCN, affording compounds [Ru(κ2-2,2′-{1-(1′-closo-1′,2′-C2B10H10)-closo-1,2-C2B10H10})(arene)(NCMe)] (5a, 5b, and 5d) and suggesting that I, 4b, and 4d could act as Lewis acid catalysts, which is subsequently shown to be the case for the Diels-Alder cycloaddition reactions between cyclopentadiene and methacrolein, ethylacrolein and E-crotonaldehyde. All new species were characterized by multinuclear NMR spectroscopy and 1a, 1c, 1d, 2c, 2d, 3b, 3c, 4b, 4d, 5a, 5b, and 5d were also characterized crystallographically.
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
supporting information, 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.
