- Palladium-Catalyzed, Atmospheric Pressure Carbonylation of Allylic Halides under the Influence of Sodium Hydroxide or Alkoxides. A Facile Synthesis of β,γ-Unsaturated Acids
-
The palladium-catalyzed, atmospheric-pressure carboxylation of allylic halides occurs readily in an aqueous sodium hydroxide/organic solvents two-phase system, giving β,γ-unsaturated acids.Phosphine complexes (I, L=m-(Ph2P)C6H4SO3Na; II, L=Ph3P) or Na2 (III) can be used as the catalyst.Atmospheric-pressure alkoxycarbonylation is realized under the influence of a homogeneous alcoholic solution of sodium alkoxide.Phosphine-free palladium complexes, such as 2 or III, are the favored catalyst. β,γ-Unsaturated esters are obtained in high yields.
- Okano, Tamon,Okabe, Nobuyuki,Kiji, Jitsuo
-
-
Read Online
- Palladium-Catalyzed Allyl-Allyl Reductive Coupling of Allylamines or Allylic Alcohols with H2as Sole Reductant
-
Catalytic carbon-carbon bond formation building on reductive coupling is a powerful method for the preparation of organic compounds. The identification of environmentally benign reductants is key for establishing an efficient reductive coupling reaction. Herein an efficient strategy enabling H2 as the sole reductant for the palladium-catalyzed allyl-allyl reductive coupling reaction is described. A wide range of allylamines and allylic alcohols as well as allylic ethers proceed smoothly to deliver the C-C coupling products under 1 atm of H2. Kinetic studies suggested that the dinuclear palladium species was involved in the catalytic cycle.
- Zhou, Xibing,Zhang, Guoying,Huang, Renbin,Huang, Hanmin
-
supporting information
p. 365 - 369
(2021/01/26)
-
- Monoallylation and benzylation of dicarbonyl compounds with alcohols catalysed by a cationic cobalt(iii) compound
-
Monoallylation and monoalkylation of diketones and β-keto esters with allylic and benzylic alcohols catalysed by [Cp*Co(CH3CN)3][SbF6]2(I) are reported. The method does not require any additive and affords regioselective products. The mechanistic investigations were done byin situ1H NMR spectroscopy as well as control experiments. It has been shown that reactions proceedviaη3-allyl complex formation or ally ether intermediate. The alkylation takes placeviaonly ether intermediate. The resulting allylated and alkylated products have been used for the synthesis of eleven new trisubstituted pyrazoles and one pyrazolone.
- Chandra Sau, Mohan,Mandal, Smita,Bhattacharjee, Manish
-
p. 9235 - 9245
(2021/03/16)
-
- Method for synthesizing ether by catalyzing alcohol through trimethyl halosilane
-
The invention discloses a method for synthesizing ether by catalyzing alcohol through trimethyl halosilane. According to the method, under the conditions of air or nitrogen atmosphere, no solvent andno transition metal catalyst, an alcohol compound is directly used as a raw material, trimethyl halosilane is used as a catalyst, and symmetric or asymmetric ether is synthesized through one-step selective dehydration reaction. According to the method, the use of strong acid, strong base and organic primary halides with high toxicity, instability and higher price is avoided, the synthesis steps are shortened, the synthesis efficiency is improved, the reaction has good selectivity, and a target ether product can be obtained preferentially.
- -
-
Paragraph 0063-0066
(2020/12/29)
-
- Radical-Cation Cascade to Aryltetralin Cyclic Ether Lignans Under Visible-Light Photoredox Catalysis
-
The development of concise, sustainable, and cost-effective synthesis of aryltetralin lignans, bearing either a fused lactone or cyclic ether, is of significant medicinal importance. Reported is that in the presence of Fukuzumi's acridinium salt under blue LED irradiation, functionalized dicinnamyl ether derivatives are converted into aryltetralin cyclic ether lignans with concurrent generation of three stereocenters in good to high yields with up to 20:1 diastereoselectivity. Oxidation of an alkene to the radical cation is key to the success of this formal Diels–Alder reaction of electronically mismatched diene and dienophile. Applying this methodology, six natural products, aglacin B, aglacin C, sulabiroin A, sulabiroin B, gaultherin C, and isoshonanin, are synthesized in only two to three steps from readily available biomass-derived monolignols. A revised structure is proposed for gaultherin C.
- Wang, Qian,Xiang, Jia-Chen,Zhu, Jieping
-
supporting information
p. 21195 - 21202
(2020/09/17)
-
- Gold(I)/Chiral N,N′-Dioxide–Nickel(II) Relay Catalysis for Asymmetric Tandem Intermolecular Hydroalkoxylation/Claisen Rearrangement
-
A highly efficient asymmetric cascade reaction between alkynyl esters and allylic alcohols has been realized. Key to success was the combination of a hydroalkoxylation reaction catalyzed by a π-acidic gold(I) complex with a Claisen rearrangement catalyzed by a chiral Lewis acidic N,N′-dioxide–nickel(II) complex. A range of acyclic α-allyl β-keto esters were synthesized in high yields (up to 99 %) with good diastereoselectivities (up to 97:3) and excellent enantioselectivities (up to 99 % ee) under mild reaction conditions. These products can be easily transformed into optically active β-hydroxy esters, β-hydroxy acids, or 1,3-diols.
- Li, Jun,Lin, Lili,Hu, Bowen,Zhou, Pengfei,Huang, Tianyu,Liu, Xiaohua,Feng, Xiaoming
-
supporting information
p. 885 - 888
(2017/01/13)
-
- Continuous-Flow Multistep Synthesis of Cinnarizine, Cyclizine, and a Buclizine Derivative from Bulk Alcohols
-
Cinnarizine, cyclizine, buclizine, and meclizine belong to a family of antihistamines that resemble each other in terms of a 1-diphenylmethylpiperazine moiety. We present the development of a four-step continuous process to generate the final antihistamines from bulk alcohols as the starting compounds. HCl is used to synthesize the intermediate chlorides in a short reaction time and excellent yields. This methodology offers an excellent way to synthesize intermediates to be used in drug synthesis. Inline separation allows the collection of pure products and their immediate consumption in the following steps. Overall isolated yields for cinnarizine, cyclizine, and a buclizine derivative are 82, 94, and 87 %, respectively. The total residence time for the four steps is 90 min with a productivity of 2 mmol h-1. The incredible bulk: Bulk alcohols are converted continuously into chlorides using HCl in a microflow. A reaction network that consists of four steps and two inline separations leads to the continuous preparation of cinnarizine, cyclizine, and a buclizine derivative with yields of 82, 94, and 87 %, respectively. The total residence time for the four steps is 90 min with a productivity of 2 mmol h-1.
- Borukhova, Svetlana,Nol, Timothy,Hessel, Volker
-
-
- Moisture-Tolerant Frustrated Lewis Pair Catalyst for Hydrogenation of Aldehydes and Ketones
-
In this paper, we report on the development of a bench-stable borane for frustrated Lewis pair catalyzed reduction of aldehydes, ketones, and enones. The deliberate fine-tuning of structural and electronic parameters of Lewis acid component and the choice of Lewis base provided for the first time, a moisture-tolerant FLP catalyst. Related NMR and DFT studies underpinned the unique behavior of this FLP catalyst and gave insight into the catalytic activity of the resulting FLP catalyst.
- Gy?m?re, ádám,Bakos, Mária,F?ldes, Tamás,Pápai, Imre,Domján, Attila,Soós, Tibor
-
p. 5366 - 5372
(2015/09/15)
-
- Organohalide-catalyzed dehydrative O-alkylation between alcohols: A facile etherification method for aliphatic ether synthesis
-
Organohalides are found to be effective catalysts for dehydrative O-alkylation reactions between alcohols, providing selective, practical, green, and easily scalable homo- and cross-etherification methods for the preparation of useful symmetrical and unsymmetrical aliphatic ethers from the readily available alcohols. Mechanistic studies revealed that organohalides are regenerated as reactive intermediates and recycled to catalyze the reactions.
- Xu, Qing,Xie, Huamei,Chen, Pingliang,Yu, Lei,Chen, Jianhui,Hu, Xingen
-
supporting information
p. 2774 - 2779
(2015/05/27)
-
- Dehydrative cross-coupling reactions of allylic alcohols with olefins
-
The direct dehydrative activation of allylic alcohols and subsequent cross-coupling with alkenes by using palladium catalyst containing a phosphoramidite ligand is described. The activation of the allyl alcohol does not require stoichiometric additives, thus allowing clean, waste-free reactions. The scope is demonstrated by application of the protocol to a series allylic alcohols and vinyl arenes, leading to variety of 1,4-diene products. Based on kinetic studies, a mechanism is proposed that involves a palladium hydride species that activates the allyl alcohol to form the allyl intermediate.
- Gumrukcu, Yasemin,De Bruin, Bas,Reek, Joost N. H.
-
supporting information
p. 10905 - 10909
(2014/09/17)
-
- Unusual behaviour of dimethyl sulfoxide towards different alcohols in the presence of cyanuric chloride
-
Dimethyl sulfoxide in combination with cyanuric chloride in dichloromethane solvent behaved differently with alcohols having different structural features. The products were obtained as methylene acetal or methyl thioether or methyl enethioether depending on the substitution pattern of the alcohols. A plausible mechanism has been proposed on the basis of isotope labeling studies.
- Chaudhuri, Subrata Kumar,Pramanik, Amit,Roy, Rimi,Khan, Sagar,Ghatak, Avishek,Bhar, Sanjay
-
p. 1773 - 1780
(2014/01/17)
-
- Hydrophobic N,N-diarylammonium pyrosulfates as dehydrative condensation catalysts under aqueous conditions
-
Oil-soluble N,N-diarylammonium pyrosulfates as nonsurfactant-type catalysts for the dehydrative ester condensation under aqueous conditions are described. Preheat treatment of dibasic sulfuric acid with bulky N,N-diarylamines generates water-tolerant salts of pyrosulfuric acid as active catalyst species. The present catalysts in water can also widely be applied to unusual selective esterifications and dehydrative glycosylation.
- Sakakura, Akira,Koshikari, Yoshiki,Akakura, Matsujiro,Ishihara, Kazuaki
-
supporting information; experimental part
p. 30 - 33
(2012/02/14)
-
- Visible light photocatalysis of [2+2] styrene cycloadditions by energy transfer
-
Hip to be square: Styrenes participate in [2+2] cycloadditions upon irradiation with visible light in the presence of an iridium(III) polypyridyl complex. In contrast to previous reports of visible light photoredox catalysis, the mechanism of this process involves photosensitization by energy transfer and not electron transfer. Copyright
- Lu, Zhan,Yoon, Tehshik P.
-
supporting information
p. 10329 - 10332,4
(2012/12/11)
-
- Pd(OAc)2/dppf as an efficient and highly active catalyst for the allylation of amines, alcohols and carboxylic acids with 1-phenyl-1-propyne
-
Pd(OAc)2/1,1′-bis(diphenylphosphino)ferrocene as an efficient, highly active catalyst for the allylation of amines, alcohols and carboxylic acids with 1-phenyl-1-propyne has been developed. The effect of various reaction parameters, such as ligand, time, solvent, temperature, metal: ligand ratio and catalyst concentration on yields of the product were investigated. The optimized procedure works well under mild operating conditions and permits rapid generation of a library for various allylated products.
- Wagh, Yogesh S.,Sawant, Dinesh N.,Tambade, Pawan J.,Dhake, Kishor P.,Bhanage, Bhalchandra M.
-
body text
p. 2414 - 2421
(2011/04/26)
-
- Allylation of 1-phenyl-1-propyne with N- and O-pronucleophiles using polymer supported triphenylphosphine palladium complex as a heterogeneous and recyclable catalyst
-
Simple methodology for the allylation of various N- and O-pronucleophiles with 1-phenyl-1-propyne as an allylating agent, using PS-TPP-Pd (polymer supported triphenylphosphine palladium) as a highly active heterogeneous recyclable catalyst has been developed. The protocol is applicable for a wide variety of hindered and functionalized aromatic amines, alcohols, and carboxylic acids. The catalyst exhibited remarkable catalytic activity for five consecutive recycles.
- Wagh, Yogesh S.,Sawant, Dinesh N.,Dhake, Kishor P.,Deshmukh, Krishna M.,Bhanage, Bhalchandra M.
-
experimental part
p. 5676 - 5679
(2011/11/06)
-
- A chiral bidentate sp2-N ligand, naph-diPIM: Application to CpRu-catalyzed asymmetric dehydrative C-, N-, and O-allylation
-
A handy new ligand: The CpRu complex (Cp=cyclopentadienyl) of a new type of chiral bisamidine ligand with a naphtho[1,2-b:7,8-b]dipyrroloimidazole (Naph-diPIM) skeleton with a Bronsted acid efficiently catalyzes dehydrative intermolecular C-allylation with high enantio- and regioselectivity. The catalytic system also gives nearly enantiomerically pure cycloalkanes and N- and O-heterocycles with a substrate/catalyst ratios of up to 10 000.
- Miyata, Kengo,Kutsuna, Hironori,Kawakami, Sho,Kitamura, Masato
-
supporting information; experimental part
p. 4649 - 4653
(2011/06/27)
-
- Platinum-catalyzed direct amination of allylic alcohols under mild conditions: Ligand and microwave effects, substrate scope, and mechanistic study
-
Transition metal-catalyzed amination of allylic compounds via a π-allylmetal intermediate is a powerful and useful method for synthesizing allylamines. Direct catalytic substitution of allylic alcohols, which forms water as the sole coproduct, has recently attracted attention for its environmental and economical advantages. Here, we describe the development of a versatile direct catalytic amination of both aryl- and alkyl-substituted allylic alcohols with various amines using Pt-Xantphos and Pt-DPEphos catalyst systems, which allows for the selective synthesis of various monoallylamines, such as the biologically active compounds Naftifine and Flunarizine, in good to high yield without need for an activator. The choice of the ligand was crucial toward achieving high catalytic activity, and we demonstrated that not only the large bite-angle but also the linker oxygen atom of the Xantphos and DPEphos ligands was highly important. In addition, microwave heating dramatically affected the catalyst activity and considerably decreased the reaction time compared with conventional heating. Furthermore, several mechanistic investigations, including 1H and 31P{1H} NMR studies; isolation and characterization of several catalytic intermediates, Pt(xantphos)Cl2, Pt(η2-C3H5OH)(xantphos), etc; confirmation of the structure of [Pt(η3-allyl)(xantphos)]OTf by X-ray crystallographic analysis; and crossover experiments, suggested that formation of the π-allylplatinum complex through the elimination of water is an irreversible rate-determining step and that the other processes in the catalytic cycle are reversible, even at room temperature.
- Ohshima, Takashi,Miyamoto, Yoshiki,Ipposhi, Junji,Nakahara, Yasuhito,Utsunomiya, Masaru,Mashima, Kazushi
-
body text
p. 14317 - 14328
(2010/02/16)
-
- Synthesis of early-transition-metal carbide and nitride nanoparticles through the urea route and their use as alkylation catalysts
-
The use of urea as either a carbon or a nitrogen source enabled the synthesis of various early-transition-metal nitride and carbide nanoparticles (TiN, NbN, Mo2N, 2N, NbCxN1-x, Mo2 C and WC). The abil
- Yao, Weitang,Makowski, Philippe,Giordano, Cristina,Goettmann, Frederic
-
scheme or table
p. 11999 - 12004
(2010/05/19)
-
- Dual palladium-and proline-catalyzed allylic alkylation of enolizable ketones and aldehydes with allylic alcohols
-
The dual Pd/proline-catalyzed α-allylation reaction of a variety of enolizable ketones and aldehydes with allylic alcohols is described. In this reaction, the choice of a large-bite angle ligand Xantphos and proline as the organocatalyst was essential for generation of the crucial π-allyl Pd intermediate from allylic alcohol, followed by nucleophilic attack of the enamine formed in situ from the corresponding enolizable carbonyl substrate and proline.
- Usui, Ippei,Schmidt, Stefan,Breit, Bernhard
-
supporting information; experimental part
p. 1453 - 1456
(2009/09/30)
-
- High-efficiency conversion of trimethylsilyl ethers to their corresponding ethers using carbon-based solid acid as a new catalyst in heterogeneous mixtures
-
Carbon-based solid acid was used as a new catalyst for conversion of trimethylsilyl ethers to their corresponding ethers in heterogeneous mixtures. The experiments were done moderately at room temperature, and high yields in suitable times were obtained under these conditions. Copyright Taylor & Francis Group, LLC.
- Shokrollahi, Arash,Zali, Abbas,Pouretedal, Hamid Reza
-
p. 371 - 375
(2008/04/01)
-
- Direct etherification of alkyl halides by sodium hydride in the presence of N,N-dimethylformamide
-
A novel synthetic method for the preparation of various alkyl ethers is described. The reaction between alkyl halides and sodium hydride in the presence of N,N-dimethylformamide afforded the corresponding symmetrical and unsymmetrical ethers in high yields. A reaction mechanism for etherification is also proposed.
- Jin, Cheng Hua,Lee, Ho Young,Lee, Sang Hwi,Kim, In Su,Jung, Young Hoon
-
p. 2695 - 2698
(2008/02/12)
-
- Reaction of orthoesters with alcohols in the presence of acidic catalysts: A study
-
Allylic and benzylic alcohols are converted into corresponding unsymmetrical ethers when reacted with various orthoesters in the presence of montmorillonite KSF at ambient temperature. A detailed study has been undertaken to examine the mechanism and generality of these reactions with regard to various acidic catalysts, which reveal interesting competitive reactions mainly O-acetylation, together with trace amount of dimerized product. The type of the side product and their relative quantity depends upon the nature of the catalyst employed. Furthermore, the low yields of the Claisen rearrangement product obtained from allylic alcohols under heating is rationalized due to the formation of some of these products.
- Sampath Kumar,Joyasawal, Sipak,Reddy,Pawan Chakravarthy,Krishna,Yadav
-
p. 1686 - 1692
(2007/10/03)
-
- Halide-Free Dehydrative Allylation Using Allylic Alcohols Promoted by a Palladium-Triphenyl Phosphite Catalyst
-
The triphenyl phosphite-palladium complex was found to effect catalytic substitution reactions of allylic alcohols via a direct C-O bond cleavage. The dehydrative etherification proceeded efficiently without any cocatalysts and bases to give allylic ethers in good to excellent yields.
- Kayaki, Yoshihito,Koda, Takashi,Ikariya, Takao
-
p. 2595 - 2597
(2007/10/03)
-
- Silica Sulfuric Acid: An Efficient Catalyst for the Direct Conversion of Primary and Secondary Trimethylsilyl Ethers to their Corresponding Ethers under Mild and Heterogeneous Conditions
-
Primary and secondary trimethylsilyl ethers were converted to their corresponding ethers in the presence silica sulfuric acid with good to excellent yields under mild and heterogeneous conditions.
- Zolfigol, Mohammad Ali,Mohammadpoor-Baltork, Iraj,Mirjalili, Bibi Fatemeh,Bamoniri, Abdolhamid
-
p. 1877 - 1879
(2007/10/03)
-
- The use of Nafion-H as an efficient catalyst for the direct conversion of primary and secondary trimethylsilyl ethers to their corresponding ethers under mild and heterogeneous conditions
-
Primary and secondary trimethylsilyl ethers were converted to their corresponding ethers in the presence Nafion-H with good to excellent yields under mild and heterogeneous conditions.
- Zolfigol, Mohammad Ali,Mohammadpoor-Baltork, Iraj,Habibi, Davood,Mirjalili, BiBi Fatemeh,Bamoniri, Abdolhamid
-
p. 8165 - 8167
(2007/10/03)
-
- Silica sulfuric acid as an efficient reagent for the synthesis of symmetrical ethers under mild and heterogeneous conditions
-
A mild and efficient method for the synthesis of symmetrical ethers using silica sulfuric acid is reported. All reactions are performed under compeletly heterogeneous conditions in good to high yields.
- Shirini, Farhad,Zolfigol, Mohammad Ali,Mohammadi, Kamal
-
p. 2357 - 2361
(2007/10/03)
-
- α-Oximono-esters as precursors to heterocycles - generation of oxazinone N-oxides and cycloaddition to alkene dipolarophiles
-
Preparation of a series of terminally and internally substituted δ-alkenyl and δ-alkynyl esters 6,7 and 9, potential precursors to oxazin-2-one nitrones, has been attempted. Condensation between pyruvic or benzoylformic acid and the appropriate alcohol pr
- Heaney, Frances,Fenlon, Julie,O'Mahony, Colm,McArdle, Patrick,Cunningham, Desmond
-
p. 4302 - 4316
(2007/10/03)
-
- A mild and efficient method for the stereoselective formation of C-O bonds: Palladium-catalyzed allylic etherification using zinc(II) alkoxides
-
(equation presented) A highly chemo-and stereoselective palladium-catalyzed allylic etherification reaction is described. The use of zinc(II) alkoxides proved effective in promoting the addition of the oxygen nucleophile derived from aliphatic alcohols to η3-allylpalladium complexes. Using diethylzinc (0.5 equiv), 5 mol % of Pd(OAc)2, and 7.5 mol % of 2-di(tert-butyl)phosphinobiphenyl in THF, the cross-coupling reaction between various aliphatic alcohols and allylic acetates proceeded at ambient temperature to furnish allylic ethers with high stereoselectivity.
- Kim, Hahn,Lee, Chulbom
-
p. 4369 - 4371
(2007/10/03)
-
- Polystyrene-supported (catecholato)oxorhenium complexes: Catalysts for alcohol oxidation with DMSO and for deoxygenation of epoxides to alkenes with triphenylphosphine
-
Polymer-supported catalysts offer practical advantages for organic synthesis, such as improved product isolation, ease of catalyst recycling, and compatibility with parallel solution-phase techniques. We have developed the (carboxypolystyrene-catecholato)rhenium catalyst 2 derived from tyramine (=4-(2-amino-ethyl)phenol), which is effective for alcohol oxidation with dimethylsulfoxide (DMSO) and for epoxide deoxygenation with triphenylphosphine. The supported [Re(catecholato)]catalyst 2 is air- and moisture-stable and can be recovered and used repeatedly without decreasing activity. The procedures work with non-halogenated solvents (toluene). DMSO for Re-catalyzed alcohol oxidation is inexpensive and safer for transport and storage than commonly used peroxide reagents. The oxidation procedure was best suited for aliphatic alcohols, and the mild conditions were compatible with unprotected functional groups, such as those of alkenes, phenols, nitro compounds, and ketones (see Tables 1 and 2). Selective oxidation of secondary alcohols in the presence of primary alcohols was possible, and with longer reaction time, primary alcohols were converted to aldehydes without overoxidation. Epoxides (oxirans) were catalytically deoxygenated to alkenes with this catalyst and Ph3P (see Table 3). Alkyloxiranes were converted to the alkenes with retention of configuration, while partial isomerization was observed in the deoxygenation of cis-stilbene oxide (cis-1.2-diphenyloxirane). These studies indicate that supported [Re(catecholato)] complexes are effective catalysts for O-atom-transfer reactions, and are well suited for applications in organic synthesis.
- Arterburn, Jeffrey B.,Liu, Minghua,Perry, Marc C.
-
p. 3225 - 3236
(2007/10/03)
-
- Reactions of the Ethers of 2,2-Dibromo-1-hydroxymethylcyclopropane with Methyllithium. Diastereoselectivity in the Synthesis and Transformations of 2-R-Oxabicyclo[3.1.0]hexanes
-
In reactions of the ethers of 2,2-dibromo-1-hydroxymethylcyclopropane with methyllithium predominant formation of derivatives of the endo-2-R-3-oxabicyclo[3.1.0]hexane was observed. The reactions in the first stage yield cyclopropylidenes which subsequent
- Bolesov,Tverezovskii,Grishin
-
p. 817 - 829
(2007/10/03)
-
- The reaction of superoxide with cinnamyl bromide: The surprising formation of an ether and an epoxy acetal
-
The reaction of O2-· (KO2/18-crown-6 in toluene) with cinnamyl bromide yielded neither the expected cinnamyl peroxide nor its Kornblum-DeLaMare fragmentation products, cinnamaldehyde (4) and cinnamyl alcohol. Instead we ob
- Frimer, Aryeh A.,Strul, Gila,Gilinsky-Sharon, Pessia
-
p. 6337 - 6342
(2007/10/02)
-
- Formation of α,β-unsaturated carbonyl compounds by palladium-catalyzed oxidation of allylic alcohols
-
Treatment of allylic alcohols with catalytic amounts of palladium catalysts in the presence of oxygen leads to the formation of α,β-unsaturated carbonyl compounds.
- Gomez-Bengoa, Enrique,Noheda, Pedro,Echavarren, Antonio M.
-
p. 7097 - 7098
(2007/10/02)
-
- Palladium(0)-Catalyzed Allylic Substitution with Allylic Alkoxides as Substrates
-
A new method has been developed which allows palladium(0)-cayalyzed allylic substitution to occur between allylic alcohols and anionic C-nucleophiles: on reaction with Ph3B, the allylic alkoxide 2 is first converted in situ into the more reactive species 3 which then undergoes a Pd(0)-catalyzed reaction with lithio diethyl malonate via the η3-complex 6.Allylic alkoxides can be generated in situ either by deprotonation of the corresponding alcohol (1 -> 2, e.g. with BuLi), via a vinylmagnesium haalide addition to the corresponding aldehyde (4 + 5 -> 2), or by hydride reduction (DIBAH) of α,β-unsaturated ketones (31 -> 32).The whole sequence can be carried out as a one pot procedure and is suitable for sensitive allylic alcohols that might be difficult to handle in pure state.While primary allylic alcohols (7 and 18) and their allylic isomers (14 and 15) give mixtures of mono- and bis-allylated products with LiCH(CO2Et)2, exclusive monoallylation has been observed for secondary alcohols (21, 23, and 26).
- Stary, Ivo,Stara, Irena G.,Kocovsky, Pavel
-
p. 529 - 538
(2007/10/02)
-
- Studies on the Conversions of Diols and Cyclic Ethers. Dehydration of Alcohols and Diols on the Action of Dimethylsulfoxide
-
The transformations of 13 alcohols and 13 diols in the presence of a small amount dimethylsulfoxide (1/16 mol) were studied.Relationships were found between the type of the hydroxy compound and the selectivity of the transformation, and conclusions were drawn regarding the transformation mechanism.The ether formation observed with certain alcohols proceeds via a carbenium cation.The reaction conditions applied were found suitable for including water elimination from the ditertiary 1,2- and 1,3-diols (pinacol rearrangement, 1,2-elimination).From the 1,4- and 1,5-diols the corresponding oxacycloalkanes can be obtained in good yield.Cyclodehydration occurs by intramolecular nucleophilic substitution, via a concerted mechanism.The effect of DMSO is excerted directly, and proton-catalysis occurs simultaneously.
- Molnar, Arpad,Bartok, Mihaly
-
p. 389 - 398
(2007/10/02)
-