- A polystyrene-supported 9-amino(9-deoxy)epi quinine derivative for continuous flow asymmetric Michael reactions
-
A polystyrene (PS)-supported 9-amino(9-deoxy)epi quinine derivative catalyzes Michael reactions affording excellent levels of conversion and enantioselectivity using different nucleophiles and structurally diverse enones. The highly recyclable, immobilized catalyst has been used to implement a single-pass, continuous flow process (residence time: 40 min) that can be operated for 21 hours without significant decrease in conversion and with improved enantioselectivity with respect to batch operation. The flow process has also been used for the sequential preparation of a small library of enantioenriched Michael adducts.
- Izquierdo, Javier,Ayats, Carles,Henseler, Andrea H.,Pericàs, Miquel A.
-
supporting information
p. 4204 - 4209
(2015/04/14)
-
- Silicone as an organosilicon reagent 2. Rhodium-catalyzed conjugate addition of the silicone reagent to α,β-unsaturated carbonyl compounds
-
The reaction of poly(phenylmethylsiloxane) with α,β-unsaturated carbonyl compounds in the presence of aqueous K2CO3 and 3 mol% of [Rh(OH)(cod)]2 gives 1,4-conjugate addition product in good yields. Arylchlorosilanes also u
- Koike, Tooru,Du, Xiaoli,Mori, Atsunori,Osakada, Kohtaro
-
p. 301 - 303
(2007/10/03)
-
- Predominant 1,2-insertion of styrene in the Pd-catalyzed alternating copolymerization with carbon monoxide
-
The regioselectivity of styrene insertion to an acyl-Pd bond was studied by NMR in (i) a stoichiomeric reaction and (ii) a copolymerization with CO. In the stoichiometric reaction of styrene with [(CH3CO)Pd-(CH3CN){(R,S)-BINAPHOS}] ·[B{3,5-(CF3)2C6 H3}4], both 1,2-and 2,1-products were given. To mimic the real polymerization conditions, a polyketone-substituted complex [{CH3(CH2CHCH3CO)n}Pd{(R,S)-BINAP HOS}]·[B(3,5-(CF3)2C6 H3)4] (n ≈ 14) was prepared. When this polymer-attached Pd species was treated with styrene, the 1,2-insertion product was the only detectable species. Thus, exclusive 1,2-insertion is demonstrated to be responsible for the styrene-CO copolymerization, in sharp contrast to the predominant 2,1-insertion with conventional nitrogen ligands. Chain-end analysis revealed that β-hydride elimination took place from the 2,1-complex but not from the 1,2-complex. Thus, once 2,1-insertion occurs, rapid β-hydride elimination proceeds to terminate the polymerization, as is common to the other phosphorus-ligand systems. The resulting Pd-H species re-initiates the copolymerization, as was proven by MALDI-TOF mass analysis of the product copolymers.
- Nozaki,Komaki,Kawashima,Hiyama,Matsubara
-
p. 534 - 544
(2007/10/03)
-
- Photochemical Wittig Reaction of Quasi-phosphonium Ylides
-
α-(Methoxycarbonyl)benzylidene quasi-phosphonium ylides, which are unreactive towards most carbonyl compounds, are found to undergo the Wittig reaction upon irradiation; irradiation with acyclic carbonyl compounds, e.g. benzaldehydes and acetophenones, af
- Tomioka, Hideo,Ichikawa, Naoki,Murata, Hideki
-
p. 193 - 195
(2007/10/02)
-
- A Novel Acetonylation of Carbonucleophiles via Palladium-Catalyzed Allylation with Isopropyl 2-Methylene-3,5-dioxahexyl Carbonate
-
Carbonucleophiles such as malonate esters, β-keto esters, phenylacetate ester, and phenylacetonitrile were acetonylated in high yields by allylation with isopropyl (or methyl) 2-methylene-3,5-dioxahexyl carbonate (4b or 4a) in the presence of palladium-phosphine catalyst under neutral conditions, followed by acidic hydrolysis.Adopting this procedure dihydrojasmone (7) was prepared from ethyl 3-oxononanoate (6) in an overall yield of 72percent.
- Ikeda, Isao,Gu, Xue-Ping,Okuhara, Toshio,Okahara, Mitsuo
-
-
- Asymmetric Allylic Alkylation of 1,3-Disubstituted 2-Propenyl Acetetes Catalyzed by a Chiral Ferrocenylphosphine-Palladium Complex
-
Reaction of racemic 2-propenyl acetates substituted with two different aryl groups at 1 and 3 positions with sodium acetylacetonate in the presence of a palladium catalyst containing an optically active ferrophosphine ligand gave regioisomeric allylic alkylation products of high optical purity (up to 95 percent ee).
- Hayashi, Tamio,Yamamoto, Akihiro,Ito, Yoshihiko
-
p. 177 - 180
(2007/10/02)
-
- Reactions of Ketenes. XX. Phenylketene Dimethylacetal As Synthon For the Introduction of Functionalized Phenylethyl Units
-
Phenylketene dimethylacetal (1) reacts with the α-diazoketones to give the dihydrofurans 6.These compounds, as cyclic ortho esters, can undergo dealcoholation into the furans 2 and hydrolysis into the γ-ketoesters 3 and into the γ-ketoacids 4.Cyclopropane acetal 8, obtained starting from acetal 1 and ethyl diazoacetate, by heating leads quantitatively to functionalized ester 9.These synthetic methods enlarge the sphere of applicability of the electron-rich alkene 1 as synthon in organic synthesis.
- Graziano, Liliana M.,Iesce, Rosaria M.,Scarpati, Rachele
-
p. 553 - 556
(2007/10/02)
-
- Michael Reaction of Conjugated Nitro Olefins with Carboxylic Acid Dianions and with Ester Enolates: New Synthesis of γ-Keto Acids and γ-Keto Esters
-
Base-sensitive conjugated nitro olefins 2 reacted with lithium dianions of carboxylic acids 3 or with lithium enolates of esters 4 at a low temperature of ca. -100 deg C, and subsequent treatment of the Michael adducts with aqueous acid yielded γ-keto acids 5 or esters 5' in a one-pot operation, respectively.Results of both the reactions have been compared.Some applications of the resulting γ-keto esters in organic synthesis have also been demonstrated in lactone synthesis and cyclenone annulation.
- Miyashita, Masaaki,Yamaguchi, Ryuji,Yoshikoshi, Akira
-
p. 2857 - 2863
(2007/10/02)
-
- Electrochemical Acylation and Carboxylation of Some Activated Olefins
-
The electrochemical acylation and carboxylation of some activated olefins have been investigated.Acenaphthylene yields thus on reductive electrochemical acetylation mainly the Z and E enol acetates of 1-(1,2-dihydro-1-acenaphthylidene)ethanone, whereas carboxylation followed by methylation gives trans-1,2-dimethoxycarbonyl-1,2-dihydroacenaphthene.Ethyl cinnamate can be acylated and carboxylated in the 3-position, whereas benzoylacetone could be carboxylated but not acetylated.Neither carboxylation nor acylation were able to compete with the dimerization of benzylidenemalonitrile.Cyclic voltammetry showed that carboxylation generally was faster than acetylation.
- Degrand, Chantal,Mora, Raymond,Lund, Henning
-
p. 429 - 436
(2007/10/02)
-
- NEW SYNTHESIS OF Γ-KETO ACIDS FROM NITROOLEFINS AND CARBOXYLIC ACID DIANIONS
-
As a convenient synthetic method of γ-keto acids, oxoalkylation of carboxylic acids with nitroolefins was examinated.Carboxylic acid dianions reacted with conjugated nitroolefins at low temperature (-100 deg C) and a variety of γ-keto acids were obtained on acidic workup in moderate to good yields.
- Miyashita, Masaaki,Yamaguchi, Ryuji,Yoshikoshi, Akira
-
p. 1505 - 1508
(2007/10/02)
-
- Studies on Organic Fluorine Compounds. 38. Ring-Opening Reactions of gem-Difluorocyclopropyl Ketones with Nucleophiles
-
Syntheses of gem-difluorocyclopropyl ketones (3a-d) and their reactions with nucleophiles are described.Ring-opening reaction of 3a,c,d having a hydrogen substituent at C1 adjacent to the carbonyl group with a methanolate anion gave carboxylic acid derivatives derived from C1-C2 bond scission (between the carbon atom with an acyl group and the carbon atom with fluorine substituents).On the other hand, reaction of 3a-c with a thiolate anion resulted in the C1-C3 bond cleavage (carbon-carbon bond opposite to the difluoromethylene group).
- Kobayashi, Yoshiro,Taguchi, Takeo,Morikawa, Tsutomu,Takase, Toyohiko,Takanashi, Hiroshi
-
p. 3232 - 3236
(2007/10/02)
-
- RING OPENING REACTION OF gem-DIFLUOROCYCLOPROPYL KETONES WITH NUCLEOPHILES
-
Syntheses of gem-difluorocyclopropyl ketones (3a-d) and their reactions with nucleophiles are described.Ring opening reactions of 3a, c and d with a methanolate and a thiolate anion took entirely different courses of bond scission of the cyclopropane ring.
- Kobayashi, Yoshiro,Taguchi, Takeo,Morikawa, Tsutomu,Takase, Toyohiko,Takanashi, Hiroshi
-
p. 1047 - 1050
(2007/10/02)
-
- NEW AND EFFICIENT SYNTHESIS OF γ-KETO ESTERS FROM NITRO OLEFINS
-
The Lewis acid-catalyzed reaction of nitro olefins and ketene methyl trimethylsilyl acetals afforded methyl 4-oxo-carboxylates on hydrolysis of the resulting adducts followed by treatment with diazomethane.
- Miyashita, Masaaki,Kumazawa, Toshiaki,Yoshikoshi, Akira
-
p. 1043 - 1044
(2007/10/02)
-