- Regio- and enantioselective allylic alkylation of an unsymmetrical substrate: A working model
-
The evolution of a model for understanding asymmetric allylic alkylations catalyzed by palladium with the use of ligands derived from chiral diamines and 2-diphenylphosphinobenzoic acid provides a basis for attacking the problem of regio- and enantioselec
- Trost,Toste
-
-
Read Online
- Ir(I)-catalyzed enantioselective decarboxylative allylic etherification: A general method for the asymmetric synthesis of aryl allyl ethers
-
Ir(I)-catalyzed enantioselective decarboxylative allylic etherification of aryl allyl carbonates provides aryl allyl ethers. Key to the generality and high stereoselection of the reaction is the use of the intramolecular decarboxylative allylation process
- Kim, Dongeun,Reddy, Srinivasa,Singh, Om V.,Lee, Jae Seung,Kong, Suk Bin,Han, Hyunsoo
-
p. 512 - 515
(2013/04/10)
-
- Stereoconvergent synthesis of chiral allylboronates from an E/Z mixture of allylic aryl ethers using a 6-NHC-Cu(I) catalyst
-
We present a 6-NHC-Cu(I) complex that provides α-substituted allylboronates using allylic aryl ether substrates. The method was discovered by comparison of the chemoselectivities exhibited by complexes 1a, 1b, 2, and 3. We observed that 1a preferentially reacts with electron-rich alkenes over electron-deficient alkenes. Development of an asymmetric method revealed that 1b reacts with both the E and Z isomers to provide the same absolute configuration without showing E-Z isomerization. This stereoconvergent reaction occurs with high yields (av 86%), high SN2′ selectivity (>99:1), and high ee (av 94%) and exhibits wide functional-group tolerance using pure E or Z isomer or E/Z alkene mixtures. The stereoconvergent feature enables the use of many different olefination strategies for substrate production, including cross-metathesis. Chiral allylboronates could be purified by silica gel chromatography and stored in the freezer without decomposition.
- Park, Jin Kyoon,Lackey, Hershel H.,Ondrusek, Brian A.,McQuade, D. Tyler
-
supporting information; experimental part
p. 2410 - 2413
(2011/04/25)
-
- Concise synthesis of licochalcone a through water-accelerated [3,3]-sigmatropic rearrangement of an aryl prenyl ether
-
Claisen-Schmidt condensation of 4-(tetrahydropyran-2-yloxy)acetophenone with 2-methoxy-4-[(3-methylbut-2-en-1-yl)oxy]benzaldehyde gave a THP-protected chalcone ether. Removal of the THP group under mild acidic conditions gave the corresponding chalcone ether, which underwent a water-accelerated Claisen rearrangement under microwave irradiation or heating in a sealed tube in aqueous ethanol to give a good yield of licochalcone A, which has diverse biological activities; no product of deprenylation or abnormal Claisen rearrangement was formed. The abnormal Claisen rearrangement of -substituted allyl aryl ethers is known to be a problem in [3,3]-sigmatropic rearrangement reaction; this, however, was not detected in our water-accelerated system.
- Jeon, Jae-Ho,Kim, Mi Ran,Jun, Jong-Gab
-
experimental part
p. 370 - 376
(2011/04/22)
-
- (Cyclopentadienyl)ruthenium-catalyzed regio- and enantioselective decarboxylative allylic etherification of allyl aryl and alkyl carbonates
-
(Cyclopentadienyl)tris(acetonitrile)ruthenium hexafluorophosphate {[CpRu(NCMe)3][PF6] or (cyclopentadienyl) (I·6-naphthalene)ruthenium hexafluorophosphate {[CpRu(I·6-naphthalene)][PF6]} in combination with a pyridine oxazoline ligand efficiently catalyze the decarboxylative allylic rearrangement of allyl aryl carbonates. Good levels of regio- and enantioselectivity are obtained. Starting from enantioenriched secondary carbonates, the reaction is stereospecific and the corresponding allylic ethers are obtained with net retention of configuration. An intermolecular version of this transformation was also developed using allyl alkyl carbonates as substrates. Conditions were found to obtain the corresponding products with similar selectivity as in the intramolecular process. Through the use of a hemi-labile hexacoordinated phosphate counterion, a zwitterionic air- and moisture-stable chiral ruthenium complex was synthesized and used in the enantioselective etherification reactions. This highly lipophilic metal complex can be recovered and efficiently reused in subsequent catalysis runs. Copyright
- Austeri, Martina,Linder, David,Lacour, Jerome
-
experimental part
p. 3339 - 3347
(2011/02/23)
-
- Synthesis and reactivity of complexes 2a-c, their involvement as catalyst precursors for regioselective allylic substitution reactions and related [Ru(Cp*)Cl(Ph2POMe)(RCHCHCH2)] [PF6] η3-allyl ruthenium(IV)inter
-
The synthesis of the new complexes [Ru(Cp*)(L)(MeCN) 2]-[PF6] (L = Ph2POMe or Ph2P-o- tolyl) and {Ru(Cp*)-[Ph2PCH2C(tBu)=O](MeCN)}[PF 6] (2a-c) is achieved starting from [Ru(Cp*)
- Demerseman, Bernard,Renaud, Jean-Luc,Toupet, Loic,Hubert, Claudie,Bruneau, Christian
-
p. 1371 - 1380
(2007/10/03)
-
- Regio- and enantioselective iridium-catalyzed intermolecular allylic etherification of achiral allylic carbonates with phenoxides
-
An enantioselective and regioselective iridium-catalyzed allylic etherification is described. The reaction of sodium and lithium aryloxides with achiral (E)-cinnamyl and terminal aliphatic allylic electrophiles in the presence of 2 mol % of an iridium-phosphoramidite complex provides chiral allylic aryl ethers in high yields and excellent levels of regio- and enantioselectivity. Lithium aryloxides containing a single substituent at an ortho, meta, or para position as well as sterically hindered phenoxides were tolerated. Reactions in THF displayed the most suitable balance of rate, regio-, and enantioselectivity. High ee's were also observed for the products from the reaction of alkyl (E)-allylic carbonates. Copyright
- Lopez, Fernando,Ohmura, Toshimichi,Hartwig, John F.
-
p. 3426 - 3427
(2007/10/03)
-
- Palladium( 0) -catalyzed phenoxycarbonylation of allylic carbonates
-
Phenoxycarbonylation of various allylic carbonates under various conditions in tetrahydrofuran is described. The nature and ratio of the products formed are dependent on the presence of water, carbon monoxide pressure and addition of various inorganic halides. The formation of a product arising from dimerization of the allylic carbonate is discussed.
- Goux, Catherine,Lhoste, Paul,Sinou, Denis,Masdeu, Anna
-
p. 139 - 143
(2007/10/03)
-
- Carbonylation of allylic ethers to esters
-
A method is disclosed for the production of esters by reaction of an allylic ether with carbon monoxide in the presence of a catalytically effective amount of a Group VIII noble metal catalyst and halide compound to obtain esters. The halide compound is present in an amount sufficient to prevent the catalyst from being converted into a Group VIII metal during the reaction. When the reaction is conducted in the presence of a quaternary ammonium salt the ester may be extracted by solvent extraction to minimize catalyst decomposition caused when extractive distillation is used to separate the ester.
- -
-
-