Palladium-Catalyzed Intramolecular Asymmetric Hydroamination, Hydroalkoxylation, and Hydrocarbonation of Alkynes

Abstract

A conceptually novel approach for asymmetric intramolecular hydroamination, hydroalkoxylation and hydrocarbonation of alkynes using chiral palladium catalysts are described. The reactions of the aminoalkynes 5, alkynols 7, and alkynylmethines 9 in the presence of Pd2(dba)3 x CHCl3/PhCOOH/renorphos 4 in benzene (or benzene-hexane) at 100 degrees C gave the corresponding cyclization products (nitrogen heterocycles 6, oxygen heterocycles 8, and carbocycles 10) in good yields with good enantioselectivities. The origins of enantioselectivities in the hydroamination reaction are discussed based on DFT computations.

Modular N,O‐Chelating Ligands: Group‐4 Amidate Complexes for Catalytic Hydroamination

“…[119][120][121][122][123][124][125][126][127] There have also been some chiral late-transition metals that have been investigated for enantioselective intermolecular hydroamination with activated alkene and alkyne substrates. [128][129][130][131][132][133][134] The cationic group-4 complexes that were mentioned in the preceding section are capable of asymmetric hydroamination of secondary aminoalkenes, albeit with modest enantioselectivities. [114] Very recently, Bergman and co-workers reported a number of neutral bis(amido)zirconium precatalysts for the asymmetric hydroamination of aminoalkenes which displayed ee values of up to 80 %.…”

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.…”

Synthesis of Saturated Heterocycles via Metal-Catalyzed Alkene Hydroamination or Hydroalkoxylation Reactions

“…This suggests that the enantiodetermining step is due to an irreversible and selective nucleophilic attack of the amine onto the gold-π-complex, with matched or mismatched reactivity depending on the stereochemistry of the substrate and catalyst, and not as a result of selective formation of the gold allene π complex. Yamamoto developed an asymmetric palladium-catalyzed alkyne isomerization/ hydroamination by utilizing a chiral bisphosphine ligand (R,R)-RENORPHOS in combination with catalytic Pd 2 (dba) 3 to afford enantioenriched 2-alkenylpyrrolidines 135 and -piperidines 137 in moderate to excellent enantioselectivities (Scheme 56) [90,108,109]. Although the triflate protecting group was suitable, the use of the nonafluorobutanesulfonyl (Nf) group gave better results by allowing for reduced catalyst loadings.…”