Reductive Cyclization of 1,6- and 1,7-Enynes Catalyzed by Iron Complexes
作者:Zhan Lu、Tuo Xi、Xu Chen、Heyi Zhang
DOI:10.1055/s-0035-1561957
日期:——
conducted. Iron-catalyzed reductive cyclization of 1,6- and 1,7-enynes was demonstrated by using an oxazoline iminopyridine ligand. Alcohol, ketone, ester, ether, halide, amine, amide, imine, nitrile, silyl, and alkyne groups are tolerated under the mild reaction conditions. A speculative mechanism is proposed on the basis of deuteration studies. A primary enantioselective transformation was also conducted
Rhodium‐Catalyzed Asymmetric [2+2+2] Cycloaddition of 1,6‐Enynes with Racemic Secondary Allylic Alcohols through Kinetic Resolution
作者:Shunsuke Suzuki、Yu Shibata、Ken Tanaka
DOI:10.1002/chem.202000010
日期:2020.3.23
[2+2+2] cycloaddition of 1,6-enynes with racemicsecondary allylic alcohols to produce the corresponding chiral bicyclic cyclohexenes, possessing three stereogenic centers, as a single diastereomer with excellent ee values. Mechanistic experiments revealed that the present cycloaddition proceeds through the kineticresolution of the racemicsecondary allylic alcohols, in which one enantiomer preferentially
Cobalt-Catalyzed Hydrosilylation/Cyclization of 1,6-Enynes
作者:Tuo Xi、Zhan Lu
DOI:10.1021/acs.joc.6b01555
日期:2016.10.7
An iminopyridine cobalt dichloride complex was synthesized and demonstrated as an effective precatalyst for hydrosilylation/cyclization of 1,6-enynes with silanes. Various functional groups such as amine, free aniline, ester, ether, cyano, halide, trifluoromethyl, and heterocycle were tolerated to afford a variety of silicon-containing compounds. The reaction could be scaled up to afford products on
It has been established that a cationic rhodium(I)/(R)-tol-BINAP or (R)-BINAP complex catalyzes the enantioselective [2 + 2 + 1] cycloaddition of 1,6-enynes, possessing monosubstituted alkene units, with cyclopropylideneacetamides at room temperature through the elimination of ethylene to give bicyclic (cyclopent-2-en-1-ylidene)acetamides with high enantioselectivity.
AbstractA cationic rhodium(I)/2,2′‐bis[bis(3,5‐di‐tert‐butyl‐4‐methoxyphenyl)phosphino]‐6,6′‐dimethoxy‐1,1′‐biphenyl (DTBM‐MeO‐BIPHEP) catalyst was highly efficient for the asymmetric catalytic Pauson–Khand reaction, especially for those substrates containing aryl group‐substituted alkynes. The formation of the products that were derived from a β‐hydride eliminated intermediate 5 was completely suppressed over a wide range of substrates. This reaction was a serious process competing reaction with the migratory CO insertion that led to the Pauson–Khand reaction product and often substantially ruined the chemical yield of the Pauson–Khand reaction. The advantages of this system were clearly demonstrated for previously troublesome substrates, N‐tosyl‐ (1b) and malonate‐tethered 1,6‐enynes (1c), that exhibited a higher enantioselectivity without a loss in the chemical yields. The obvious beneficial effects were attributed to the synergic effect of various factors, such as the electron density of the phosphorus of the ligand, the dihedral angles of the atropisomeric ligand, and the substitution on the phosphine aryl rings which play a crucial role in the stereochemical outcome of Rh‐catalyzed Pauson–Khand reaction.