Die Cobalt(I)‐katalysierte asymmetrische [2+2+2]‐Cycloaddition von Alkinen und Nitrilen: Synthese von enantiomerenangereicherten Atropisomeren von 2‐Arylpyridinen

Cationic Rhodium(I)/Modified‐BINAP Catalyzed [2+2+2] Cycloaddition of Alkynes with Nitriles

“…[14] In view of the application to such enantioselective [2+2+2] cycloaddition, the development of Rh-based catalysts is an attractive target. We recently reported the cationic rhodium(I)/H 8 -BINAP [2,2Ј-bis(diphenylphosphanyl)-5,5Ј,6,6Ј,7,7Ј,8,8Ј-octahydro-1,1Ј-binaphthyl] catalyzed chemo-, regio-, and enantioselective cross cyclotrimerization of two different alkynes.…”

Asymmetric Dehydrative Cyclization of ω‐Hydroxy Allyl Alcohols Catalyzed by Ruthenium Complexes

“…The development of an efficient strategy for the construction of these cyclic ethers has attracted a great deal of attention over the last two decades. In particular, the focal point is the creation of catalytic enantioselective protocols, which have been categorized into three types: 1) Wacker-type oxidative cyclization of ortho-allyl-or homoallylphenol derivatives, [2] 2) Tsuji-Trost-type intramolecular allylation using w-hydroxy allyl esters, [1c,f, 3] and 3) hydroalkoxylation of alkynes [4] and allenes.[5] Herein, we report a new type of protocol, in which non-activated or non-protected diols 1 dehydratively cyclize into the corresponding cyclic ethers 2 with high regio-and enantioselectivity.We have developed a new chiral ligand-R-naphpyCOOH 4 [naph = naphthyl, py = pyridine, R = substituent (see structures)]-based on the knowledge that a catalytic system combining [CpRu(CH 3 CN) 3 ]PF 6 (3; Cp = cyclopentadienyl) [6] with a pyridine-2-carboxylic acid derivative or the corresponding cationic CpRu IV -p-allyl carboxylato complex can convert a 1:1 mixture of alcohols or allyl alcohols into allyl ethers with the liberation of water.[7] The ligand is characterized by the sterically flexible axial chirality through the C6-C1' bond [8] and the adjustability of electronic and steric properties of the naphthalene ring by changing the R substituent at C2'. The allyl esters R-naph-pyCOOallyl (allyl = CH 2 CH = CH 2 ) 5 were also target ligands because of the convenient formation of the CpRu IV -p-allyl complex directly from 3.…”

Developing a New Class of Axial Chiral Phosphorus Ligands: Preparation and Characterization of Enantiopure Atropisomeric Phosphinines

“…[5] This modular approach also allowed us to design and synthesize the first atropisomeric phosphinine 1 (R, S) by enforcing restricted rotation around a C aryl -C aryl' bond (Scheme 1). [6,7] By using density functional theory (DFT) calculations, an energy barrier for internal rotation of DG°2 98 = 116 kJ mol À1 for the enantiomerization of 1 was predicted, which is expected to be high enough for configurational stability under ambient conditions. [8] Compound 1 was obtained as a racemic mixture, but we have already demonstrated that both enantiomers can be detected with Abstract: Both enantiomers of the first atropisomeric phosphinine (1) have been isolated by using analytical HPLC on a chiral stationary phase.…”