- Recyclable and reusable PdCl2(PPh3)2/PEG-400/H2O system for the hydrophenylation of alkynes with sodium tetraphenylborate
-
A stable and efficient PdCl2(PPh3)2/PEG-400/H2O catalytic system for the hydrophenylation reaction of alkynes has been developed. In the presence of 3 mol% PdCl2(PPh3)2 and 2 equiv. of HOAc, the hydrophenylation of both terminal and internal alkynes with sodium tetraphenylborate proceeded smoothly in a mixture of PEG-400 and water at room temperature or 50 °C to afford a variety of phenyl-substituted alkenes in moderate to high yields. The isolation of the products was easily performed by extraction with petroleum ether, and the PdCl2(PPh3)2/PEG-400/H2O system could be readily recycled and reused six times without apparent loss of catalytic activity.
- Liu, Rong,Zhang, Tingli,Huang, Bin,Cai, Mingzhong
-
p. 172 - 178
(2020/07/04)
-
- Oxoammonium-Mediated Allylsilane–Ether Coupling Reaction
-
A new C(sp3)?H functionalization reaction consisting of the oxidative α-allylation of allyl- and benzyl- methyl ethers has been developed. The C?C coupling could be carried out under mild conditions thanks to the use of cheap and green oxoammonium salts. The scope of the reaction was studied over 27 examples, considering the nature of the substituents on the two coupling partners.
- Carlet, Federica,Bertarini, Greta,Broggini, Gianluigi,Pradal, Alexandre,Poli, Giovanni
-
supporting information
p. 2162 - 2168
(2021/04/02)
-
- Dramatic Effect of γ-Heteroatom Dienolate Substituents on Counterion Assisted Asymmetric Anionic Amino-Cope Reaction Cascades
-
We report a dramatic effect on product outcomes of the lithium ion enabled amino-Cope-like anionic asymmetric cascade when different γ-dienolate heteroatom substituents are employed. For dienolates with azide, thiomethyl, and trifluoromethylthiol substituents, a Mannich/amino-Cope/cyclization cascade ensues to form chiral cyclohexenone products with two new stereocenters in an anti-relationship. For fluoride-substituted nucleophiles, a Mannich/amino-Cope cascade proceeds to afford chiral acyclic products with two new stereocenters in a syn-relationship. Bromide- and chloride-substituted nucleophiles appear to proceed via the same pathway as the fluoride albeit with the added twist of a 3-exo-trig cyclization to yield chiral cyclopropane products with three stereocenters. When this same class of nucleophiles is substituted with a γ-nitro group, the Mannich-initiated cascade is now diverted to a β-lactam product instead of the amino-Cope pathway. These anionic asymmetric cascades are solvent- and counterion-dependent, with a lithium counterion being essential in combination with etheral solvents such as MTBE and CPME. By altering the geometry of the imine double bond from E to Z, the configurations at the R1 and X stereocenters are flipped. Mechanistic, computational, substituent, and counterion studies suggest that these cascades proceed via a common Mannich-product intermediate, which then proceeds via either a chair (X = N3, SMe, or SCF3) or boat-like (X = F, Cl, or Br) transition state to afford amino-Cope-like products or β-lactam in the case of X = NO2.
- Das, Pradipta,Delost, Michael D.,Qureshi, Munaum H.,Bao, Jianhua,Fell, Jason S.,Houk, Kendall N.,Njardarson, Jon T.
-
supporting information
p. 5793 - 5804
(2021/05/07)
-
- Copper-Catalyzed 1,2-Methoxy Methoxycarbonylation of Alkenes with Methyl Formate
-
Reported here is a copper-catalyzed 1,2-methoxy methoxycarbonylation of alkenes by an unprecedented use of methyl formate as a source of both the methoxy and the methoxycarbonyl groups. This reaction transforms styrene and its derivatives into value-added β-methoxy alkanoates and cinnamates, as well as medicinally important five-membered heterocycles, such as functionalized tetrahydrofurans, γ-lactones, and pyrrolidines. A ternary β-diketiminato-CuI-styrene complex, fully characterized by NMR spectroscopy and X-ray crystallographic analysis, is capable of catalyzing the same transformation. These findings suggest that pre-coordination of electron-rich alkenes to copper might play an important role in accelerating the addition of nucleophilic radicals to electron-rich alkenes, and could have general implications in the design of novel radical-based transformations.
- Budai, Balázs,Leclair, Alexandre,Wang, Qian,Zhu, Jieping
-
supporting information
p. 10305 - 10309
(2019/06/27)
-
- DMAP-Catalyzed [4 + 2] Cycloaddition of α,β-Unsaturated Carboxylic Acids with Ketones for Synthesis of α,β-Unsaturated δ-Lactones
-
The DMAP-catalyzed [4 + 2] cycloaddition of α,β-unsaturated carboxylic acids with ketones furnishing α,β-unsaturated δ-lactones in good yields (up to 80%) is described, which is the first example of remote γ-C(sp3)-H activation of α,β-unsaturated carboxylic acids facilitated by DMAP, a pyridine-based catalyst. Copyright
- Jin, Jinghai,Xu, Qinchang,Deng, Weiping
-
supporting information
p. 397 - 400
(2017/04/27)
-
- Highly efficient synthesis of chiral aromatic ketones: Via Rh-catalyzed asymmetric hydrogenation of β,β-disubstituted enones
-
A succinct and efficient protocol was developed for the synthesis of chiral aromatic ketones via asymmetric hydrogenation of β,β-disubstituted enones with rhodium catalysts based on chiral bisphosphine thiourea ligands. A series of substrates (17 examples) was smoothly catalyzed to afford the corresponding chiral aromatic ketones in high conversions (>99%) with excellent enantioselectivities (up to 96% ee).
- Zhang, Tao,Jiang, Jun,Yao, Lin,Geng, Huiling,Zhang, Xumu
-
supporting information
p. 9258 - 9261
(2017/08/22)
-
- Rhodium-Catalyzed Asymmetric Hydrogenation of α,β-Unsaturated Carbonyl Compounds via Thiourea Hydrogen Bonding
-
The strategy of secondary interaction enables enantioselectivity for homogeneous hydrogenation. By introducing hydrogen bonding of substrates with thiourea from the ligand, α,β-unsaturated carbonyl compounds, such as amides and esters, are hydrogenated wi
- Wen, Jialin,Jiang, Jun,Zhang, Xumu
-
supporting information
p. 4451 - 4453
(2016/09/28)
-
- Palladium-Catalyzed Arylation of Olefins by Triarylphosphines via C-P Bond Cleavage
-
C-H Arylation of olefins by triarylphosphines via C-P bond cleavage has been achieved with either Pd0 or PdII catalysts. A variety of olefins and triarylphosphines are tolerated, and we inferred that both Pd0 and PdII could function directly without pre-oxidation or pre-reduction.
- Lu, Dapeng,Xu, Yu,Liu, Wenjing,Guo, Lijuan,Sun, Xingxia
-
p. 116 - 122
(2015/10/19)
-
- Gallium-assisted transfer hydrogenation of alkenes
-
We report a rare case of alkene transfer hydrogenation using a main-group compound instead of a transition-metal complex as catalyst. We disclosed that 1, 4-cyclo-hexadiene can be used as H2 surrogate towards olefin reduction in the presence of [IPrGaCl2][SbF6]. Hydrogenative cycli-zations have also been carried out because this cationic gallium complex is also a potent hydroarylation catalyst.
- Michelet, Bastien,Bour, Christophe,Gandon, Vincent
-
supporting information
p. 14488 - 14492
(2015/04/16)
-
- Pd-arylurea complexes for the Heck arylation of crotonic and cinnamic substrates
-
A catalyst consisting of the 1:2 complex of Pd(OAc)2 (1 mol %) with N-(4-carbethoxy)-phenylurea promotes the Heck arylation of a range of crotonic and cinnamic substrates, including aldehydes, ketones, esters, and nitriles, with electron-rich - but not electron-deficient - aryl iodides.
- Smith, Matthew R.,Kim, Jung Yun,Ciufolini, Marco A.
-
supporting information
p. 2042 - 2045
(2013/04/24)
-
- Palladium-catalyzed arylation of enoates with iodobenzene: Stereoselective synthesis of trisubstituted olefins
-
The Heck reaction between E- and Z-enoates and iodobenzene was studied in the presence of Pd(OAc)2. The stereochemistry in resulting adducts was dependent on the enoate geometry (stereospecific reaction). Best yields were obtained from Z-isomer
- De Fernandes, Talita A.,Vaz, Boniek G.,Da Silva, Alcides J.M.,Esteves, Pierre M.,Eberlin, Marcos N.,Costa, Paulo R.R.
-
p. 500 - 506
(2013/08/25)
-
- Highly porous chitosan microspheres supported palladium catalyst for coupling reactions in organic and aqueous solutions
-
Porous chitosan microspheres (PCMS) were prepared from crosslinking chitosan/polyethylene glycol (PEG) interpenetrating microspheres through selective dissolution of the water-soluble PEG component for the immobilization of palladium catalyst. The resultant Pd/PCMS supported palladium has been demonstrated as a highly active and easily recyclable heterogeneous catalyst for the Ullmann-type reductive homocoupling of aromatic halides and the Heck cross-coupling of aromatic halides with acrylates. Most interestingly, the prepared Pd/PCMS heterogeneous palladium catalyst can also be employed in the environmentally-benign aqueous solution due to the highly hydrophilic hydroxyl and amino functional groups of chitosan. The large size of the microsphere structure can greatly facilitate separation and recycling of the expensive and toxic palladium catalysts from the reaction mixture and the recovered Pd/PCMS catalyst can preserve the catalytic activity and selectivity for the Heck reaction without any observable degradation over ten recycling times. The high activity and stability of the Pd/PCMS catalyst have been attributed to a combination of the high specific surface area of the porous structure as well as the strong chelation of palladium species with the abundant chitosan surface hydroxyl, amino and carbonyl functional groups.
- Zeng, Minfeng,Zhang, Xin,Shao, Linjun,Qi, Chenze,Zhang, Xian-Man
-
experimental part
p. 29 - 37
(2012/04/04)
-
- Synthesis, modeling and functional activity of substituted styrene-amides as small-molecule CXCR7 agonists
-
The chemokine receptor CXCR7 is an atypical G protein-coupled receptor as it preferentially signals through the β-arrestin pathway rather than through G proteins. CXCR7 is thought to be of importance in cancer and the development of CXCR7-targeting ligands is of huge importance to further elucidate the pharmacology and the therapeutic potential of CXCR7. In the present study, we synthesized 24 derivatives based on a compound scaffold patented by Chemocentryx and obtained CXCR7 ligands with pKi values ranging from 5.3 to 8.1. SAR studies were supported by computational 3D Fingerprint studies, revealing several important affinity descriptors. Two key compounds (29 and 30, VUF11207 and VUF11403) were found to be high-potency ligands that induce recruitment of β-arrestin2 and subsequent internalization of CXCR7, making them important tool compounds in future CXCR7 research.
- Wijtmans, Maikel,Maussang, David,Sirci, Francesco,Scholten, Danny J.,Canals, Meritxell,Muji?-Deli?, Azra,Chong, Milagros,Chatalic, Kristell L.S.,Custers, Hans,Janssen, Elwin,De Graaf, Chris,Smit, Martine J.,De Esch, Iwan J.P.,Leurs, Rob
-
supporting information; experimental part
p. 184 - 192
(2012/07/14)
-
- Pyridine ligands as promoters in PdII/0-catalyzed C-H olefination reactions
-
Commercially available pyridine ligands can significantly enhance the rate, yield, substrate scope, and site selectivity of arene C-H olefination (Fujiwara-Moritani) reactions. The use of a 1:1 ratio of Pd/pyridine proved critical to maximize reaction rates and yields.
- Kubota, Asako,Emmert, Marion H.,Sanford, Melanie S.
-
supporting information; experimental part
p. 1760 - 1763
(2012/05/20)
-
- An efficient procedure based on a MW-assisted Horner-Wadsworth-Emmons reaction for the synthesis of (Z)-3,3-trisubstituted-α,β-unsaturated esters
-
A microwave-assisted HWE olefination process of readily accessible aryl-alkyl ketones has been developed to provide a rapid access to (Z)-3,3-trisubstituted-α,β-unsaturated methyl esters, key building blocks for the synthesis of biologically active compou
- Rossi, Daniela,Baraglia, Anna Carnevale,Serra, Massimo,Azzolina, Ornella,Collina, Simona
-
experimental part
p. 5928 - 5942
(2010/12/18)
-
- Mild, efficient, and robust method for stereocomplementary iron-catalyzed cross-coupling using (E)- and (Z)-enol tosylates
-
Iron-catalyzed cross-coupling of Grignard reagents (RMgX) with (E)- and (Z)-enol tosylates proceeded smoothly to give a variety of the corresponding (E)- and (Z)-trisubstituted ,-unsaturated methyl esters (total 30 examples; 55-98% yield). The simple, mild, stereoretentive method utilized iron(III) chloride (FeCl3), iron(III) acetylacetonate [Fe(acac)3], and iron(III) tris(dibenzylmethane) [Fe(dbm). The (E)- and (Z)-enol tosylates were readily prepared by the reported stereocomplementary tosylation method from methyl -keto esters or -formyl esters. Methyl -formyl esters were obtained via a practical and robust TiCl4-Et3N-mediated -formylation of methyl esters with methyl formate.
- Nishikado, Hiroshi,Nakatsuji, Hidefumi,Ueno, Kanako,Nagase, Ryohei,Tanabe, Yoo
-
experimental part
p. 2087 - 2092
(2010/10/03)
-
- P[N(i-Bu)CH2CH2]3N: Nonionic Lewis base for promoting the room-temperature synthesis of α,β-unsaturated esters, fluorides, ketones, and nitriles using Wadsworth - Emmons phosphonates
-
The bicyclic triaminophosphine P(RNCH2CH2) 3N (R = i-Bu, 1c) serves as an effective promoter for the room-temperature stereoselective synthesis of α,β-unsaturated esters, fluorides, and nitriles from a wide array of aromatic, aliphatic, heterocyclic, and cyclic aldehydes and ketones, using a range of Wadsworth-Emmons (WE) phosphonates. Among the analogues of 1c [R = Me (1a), i-Pr (1b), Bn (1d)], 1a and 1b performed well, although longer reaction times were involved, and 1d led to poorer yields than 1c. Functionalities such as cyano, chloro, bromo, methoxy, amino, ester, and nitro were well tolerated. We were able to isolate and characterize (by X-ray means; see above) the reactive WE intermediate species formed from 2b and 1c.
- Chintareddy, Venkat Reddy,Ellern, Arkady,Verkade, John G.
-
supporting information; experimental part
p. 7166 - 7174
(2010/12/25)
-
- Enantioselective Rh-catalyzed hydrogenation of 3-aryl-4-phosphonobutenoates with a P-stereogenic BoPhoz-type ligand
-
A series of chiral 3-aryl-4-phosphonobutyric acid esters were synthesized in high enantioselectivities (93-98% ee) via the Rh-catalyzed asymmetric hydrogenation of the corresponding 3-aryl-4-phosphonobutenoates using a P-stereogenic BoPhoz-type phosphine-aminophosphine ligand. The methodology has been successfully applied to the asymmetric synthesis of a potential GABA B antagonist, (R)-phaclofen, in high enantioselectivity.
- Duan, Zheng-Chao,Hu, Xiang-Ping,Zhang, Cheng,Zheng, Zhuo
-
supporting information; experimental part
p. 8319 - 8321
(2011/03/17)
-
- Palladium-catalyzed hydrophenylation of alkynes with sodium tetraphenylborate under mild conditions
-
(Chemical Equation Presented) In an aqueous solution of acetic acid, PdCl2(PPh3)2 showed high catalytic activity for the hydrophenylation of both terminal and internal alkynes with sodium tetraphenylborate (NaBPh4) under mild conditions, affording phenyl alkenes in moderate to excellent yields.
- Zeng, Hanxiang,Hua, Ruimao
-
p. 558 - 562
(2008/09/17)
-
- General, robust, and stereocomplementary preparation of β-ketoester enol tosylates as cross-coupling partners utilizing TsCl-N-methylimidazole agents
-
(Chemical Equation Presented) We have developed a general, robust, and cost-effective method for the (E)- or (Z)-stereocomplementary enol tosylation of β-ketoesters using TsCl-N-methylimidazole (NMI)-Et3N or LiOH. TsCl coupled with NMI formed a
- Nakatsuji, Hidefumi,Ueno, Kanako,Misaki, Tomonori,Tanabe, Yoo
-
supporting information; scheme or table
p. 2131 - 2134
(2009/05/26)
-
- Oxygen and base-free oxidative heck reactions of arylboronic acids with olefins
-
A mild and efficient protocol for palladium-catalyzed oxidative Heck reactions of arylboronic acids with both electron-rich and -deficient olefins is described. In contrast to the normal oxidative Heck coupling, this new method works in the absence of a base, oxygen, or other external oxidants. With a wide variety of substrates tolerated, the method broadens the scope of palladium-catalyzed coupling reactions. Copyright
- Ruan, Jiwu,Li, Xinming,Saidi, Ourida,Xiao, Jianliang
-
p. 2424 - 2425
(2008/09/18)
-
- Palladium-catalyzed enantioselective conjugate addition of arylboronic acids
-
(Chemical Equation Presented) The first asymmetric palladium-catalyzed conjugate addition of arylboronic acids to α,β-unsaturated aldehydes, ketones, and esters is described. For cyclic substrates, excellent chemo-, regio-, and enantioselectivities are achieved when a Pd(O2CCF 3)2/DuPHOS catalyst is applied.
- Gini, Francesca,Hessen, Bart,Minnaard, Adriaan J.
-
p. 5309 - 5312
(2007/10/03)
-
- Sterically bulky thioureas as air- and moisture-stable ligands for pd-catalyzed heck reactions of aryl halides
-
We demonstrate that sterically bulky N,N′-disubstituted cyclic thiourea-Pd(0) complexes are air- and moisture-stable and highly active catalysts for palladium-catalyzed Heck reaction of aryl iodides and bromides with olefins (TONs up to 500 000 for the reaction of Phl and methyl acrylate). Even activated aryl chlorides can undergo complete conversion in Bu 4NBr in the presence of 1 mol % Pd catalyst.
- Yang, Dan,Chen, Ying-Chun,Zhu, Nian-Yong
-
p. 1577 - 1580
(2007/10/03)
-
- Mesyloxy-group migration as the stereoselective preparation method of various functionalized olefins and its reaction mechanism
-
It was demonstrated that mesylation of appropriate γ,γ-difluorinated allylic alcohols under usual conditions furnished the corresponding α,γ-difluorinated allylic mesylates, possibly by way of 1,3-mesyloxy-group migration after formation of the expected "normal" intermediates, γ,γ-difluorinated allylic mesylates. This rearrangement was conveniently applied to the construction of trisubstituted allylic alcohols, α,β-unsaturated esters, amides, or ketones in good to excellent chemical yields with exclusive E selectivities.
- Yamazaki, Takashi,Hiraoka, Shuichi,Sakamoto, Johei,Kitazume, Tomoya
-
p. 743 - 746
(2007/10/03)
-
- A versatile catalyst for heck reactions of aryl chlorides and aryl bromides under mild conditions
-
In the presence of Cy2NMe, Pd/P(t-Bu)3 serves as an exceptionally mild and versatile catalyst for Heck reactions of aryl chlorides and bromides. A sterically and electronically diverse array of aryl bromides, as well as activated aryl chlorides, couple with a range of mono- and disubstituted olefins at room temperature, furnishing the arylated product with high E/Z stereoselection. The corresponding reactions of a broad spectrum of electron-neutral and electron-rich aryl chlorides proceed at elevated temperature, also with high selectivity. In terms of scope and mildness, Pd/P(t-Bu)3/Cy2NMe represents an advance over previously reported catalysts for these Heck coupling processes.
- Littke,Fu
-
p. 6989 - 7000
(2007/10/03)
-
- Highly active Pd(II) cyclometallated imine catalysts for the Heck reaction
-
The new cyclopalladated, phosphine-free imine complexes 1-3 are exceptional catalysts for the Heck arylation, leading to more than a million turnovers in some cases; the catalysts are very thermally and air stable and are recovered unchanged after the catalysis.
- Ohff, Manuela,Ohff, Andreas,Milstein, David
-
p. 357 - 358
(2007/10/03)
-
- New approaches towards the synthesis of alkenes using the Horner-Wadsworth-Emmons (HWE) reaction as the key step
-
Leading from our work in asymmetric alkene synthesis it was discovered that the alkenylatio of aldehydes with phosphonates proceeds smoothly at room temperature in the absence of Lewis acidusing triethylamine as the base if the reaction is carried out at a pressure of 8 kbar. Based on this protoco a new domino process was developed, combining the HWE reaction with a Heck coupling, thus allowing the one pot synthesis of trisubstituted alkenes.
- Bodman, Kerstin,Has-Becker, Shenay,Reiser, Oliver
-
p. 173 - 176
(2007/10/03)
-
- Zinc metal-promoted stereoselective olefination of aldehydes and ketones with gem-dichloro compounds in the presence of chlorotrimethylsilane
-
A combination of zinc metal and a catalytic amount of chlorotrimethylsilane has been found to promote the transformation of various aldehydes and ketones with gem-dichloro compounds, such as benzylidene dichloride (1a) and methyl dichloroacetate (1b), to the corresponding cross- coupling products, such as substituted styrene 3 and methyl acrylates 4 derivatives, under mild reaction conditions in THF. The E-isomer of the corresponding alkenes was obtained stereoselectively in good-to-excellent yields. The reaction serves as a very convenient one-pot procedure.
- Ishino, Yoshio,Mihara, Masatoshi,Nishihama, Shintaro,Nishiguchi, Ikuzou
-
p. 2669 - 2672
(2007/10/03)
-
- New reaction mode of the Horner-Wadsworth-Emmons reaction using Sn(OSO2CF3)2 and N-ethylpiperidine
-
Excellent Z or E selectivity is observed in the Horner-Wadsworth-Emmons reactions of methyl bis(trifluoroethyl)phosphonoacetate 2 with aryl alkyl ketones 3a-d or aldehydes 3f,g using Sn(OSO2CF3)2 in the presence of N-ethylpiperidine, which should have a different reaction mode to those using sodium hydride.
- Sano, Shigeki,Yokoyama, Kenji,Fukushima, Mari,Yagi, Tetsuo,Nagao, Yoshimitsu
-
p. 559 - 560
(2007/10/03)
-
- Wittig reactions in the presence of silica gel
-
Wittig reactions, of stable phosphorous ylids, when carried out in presence of silica gel, in hexane, provide a fast, efficient and simple method to obtain α:β unsaturated compounds in high yields and high purity.
- Patil, Vijay J.,Maevers, Ursula
-
p. 1281 - 1284
(2007/10/03)
-
- Synthesis and Properties of Cationic Organopalladium Complexes. Remarkable Rate Enhancement in Olefin Insertion into the Palladium-Aryl Bond by the Generation of a Cationic Palladium Complex from trans-
-
By removing the bromide ligand in trans- (1) by AgBF4 in the presence and absence of pyridine, pyridine-coordinated and solvent-coordinated cationic complexes, trans-BF4 (2) and trans-BF4 (3) have been obtained.These cationic phenylpalladium complexes show much greater reactivities than do the parent neutral complex 1 toward olefins to give phenylated olefins by insertion followed by β-hydrogen elimination processes.Kinetic studies concerning the insertion of methyl acrylate into the phenyl-palladium bond have indicated that the reactions are first order in the phenylpalladium complexes and that addition of pyridine to a system containing 2 and methyl acrylate inhibits the insertion reaction of the olefin.The results suggest that the generation of a cationic arylpalladium complex with a vacant site is important for the olefins to be inserted.
- Kawataka, Futoshi,Shimizu, Isao,Yamamoto, Akio
-
p. 654 - 660
(2007/10/02)
-
- The Kharasch reaction revisited: CuX3Li2-catalyzed conjugate addition reactions of Grignard reagents
-
The conjugate addition of Grignard reagents RMgX to α,β-unsaturated ketones and esters is effectively catalyzed by soluble copper ate-complexes of the type CuX3Li2, e.g.CuI*2LiCl.In the presence of Me3SiCl the corresponding ketone enolsilanes are formed in high yield and selectivity.Diastereoselectivity in the case of chiral ketones is similar to that observed by using stoichiometric amounts of cuprates R2CuLi.Thus CuX3Li2-catalyzed 1,4-additions of Grignard reagents may be an industrially viable process.Keywords: Copper; Magnesium; Lithium; Silicon; Ketone; Enolsilanes
- Reetz, Manfred T.,Kindler, Alois
-
-
- Electron Transfer Profile of Cyclopropanone Acetals in the Nonirradiated Reaction with Tetracyanoethylene, Chloranil, and Dicyanodichlorobenzoquinone
-
The donor profiles of cyclopropanone acetals 1 and 2 were examined in the reactions with electron acceptors (TCNE, DDQ, chloranil, and 1-cyanonaphthalene).With TCNE under nonirradiating conditions, an exclusive 2 + 2 cycloaddition took place stereospecifically with monosubstituted acetals 1a-c but nonstereospecifically with disubstituted acetals 1d,e.With quinones, a ring-opening of the cyclopropane and its coupling with the quinone took place to give the C (cyclopropane)-O (quinone) adduct 9 (with chloranil) or 10 (with DDQ), the latter of which underwent the elimination of a phenol to produce unsaturated esters 5 and 6.In addition, the intervention of the C (cyclopropane)-C (quinone) adduct 14 (with chloranil) or 15 (with DDQ), both as the precursor of 5 and 6, was also postulated.With 1-cyanonaphthalene, under photolysis, the cis/trans isomerization of 1 and 2 occured.The results provided evidences that cyclopropanone acetals, in general, are prone to function as donors.The mechanism of the reaction with quinones, in particular, was investigated in detail.
- Oku, Akira,Abe, Manabu,Iwamoto, Masaharu
-
p. 7445 - 7452
(2007/10/02)
-
- Formation of Unsaturated Esters in the Single Electron Transfer Reaction of Cyclopropanone Acetals with Quinones under Non-irradiated Conditions
-
Unsaturated esters were formed from cyclopropanone aceytals in the reaction with DDQ or chloranil, where ring-opened C-C and C-O bonded adducts were the intermediates formed via a SET mechanism resulting in the ester formation.
- Abe, Manabu,Oku, Akira
-
p. 3551 - 3554
(2007/10/02)
-
- Remarkable reversal of stereoselectivity in Wittig-type olefinations of α-fluorinated alkyl aryl ketones
-
Remarkable reactivity and reversal of stereoselectivity in the Wittig-type olefinations of α-fluorinated alkyl aryl ketones were described. Stabilized Wittig and Horner-Emmons reagents with these ketones selectively afforded the olefinic products in the stereochemically opposite fashion to the non-fluorinated ketone cases. The Still's reagent further reversed the stereochemical outcome with the fluorinated ketones.
- Eguchi,Aoyama,Kakinuma
-
p. 5545 - 5546
(2007/10/02)
-
- THE REGIOSELECTIVE PREPARATION OF 1-ALKEN-3-ONES BY THE REACTION OF 3-(1-IMIDAZOLYL)-2-ALKEN-1-ONES WITH ORGANOMETALLIC COMPOUNDS
-
3-(1-Imidazolyl)-2-alken-1-ones, having substituent on the C-3 carbon, reacted with organometallic compounds to afford 3-(1-imidazolyl)-2-alken-1-ols.By the treatment of the products with sulfuric acid, 1-alken-3-ones, which were the positional isomers of the Michael addition products, was obtained regioselectively in good yields under mild conditions.Sodium borohydride reduction was also investigated.
- Kashima, Choji,Hibi, Shigeki,Shimizu, Masao,Tajima, Tadakuni,Omote, Yoshimori
-
p. 429 - 436
(2007/10/02)
-
- Polarized Ketene Dithioacetals. Part 42. Studies on the Reactions of Alkyl and Aryl Grignard Reagents with α-Oxoketene Dithioacetals
-
The oxoketene dithioacetals (2a-k) derived from a variety of cyclic and acyclic active methylene ketones undergo 1,2-addition with methylmagnesium iodide to give the alcohol acetals (3a-k) which, on subsequent boron trifluoride-ether catalysed methanolysi
- Singh, Gurdeep,Purkayastha, Makhan L.,Ila, Hiriyakkanavar,Junjappa, Hiriyakkanavar
-
p. 1289 - 1294
(2007/10/02)
-
- Polarized Ketene Dithioacetals. 28. A New General Highly Stereoselective and Regiospecific Method for Homologation of Ketones to α,β-Unsaturated Esters via α-Oxoketene Dithioacetals
-
A new highly stereoselective and regiospecific general method for the conversion of active methylene ketones to α,β-unsaturated O-methyl esters, S-methyl esters, and aldehydes via the corresponding oxoketene dithioacetals has been developed.Thus the carbinols 7a-g obtained by sodium borohydride reduction of the corresponding oxoketene dithioacetals 6a-g, derived from acetophenones and their higher homologues, have been shown to undergo boron trifluoride etherate assisted methanolysis to give the corresponding (E)-methylcinnamates 3a-d and their α-alkyl derivatives 3e-g in high yields.Also the acetals 6h-k derived from alkylmethyl ketones gave the corresponding (E)-methylcrotonates 3h-k.Similarly, the acetals 6l-p derived from alicyclic ketones gave the corresponding cyclic ene esters 3l-p under identical conditions.A few carbinols, 7a-d, were shown to undergo partial hydrolysis in the presence of boron trifluoride etherate/water to give the corresponding S-methyl thiocinnamates 8a-d.The cyclic acetals 6l-n were also similarly converted to the corresponding cyclic S-methylene thio esters 8e-g.The (methylthio)alkenyl ketones 20a-d and 18 after borohydride reduction and acidic hydrolysis gave the corresponding (E)-α,β-unsaturated aldehydes 22a-d and 19.The mechanism governing these transformations has been proposed.
- Myrboh, Bekington,Ila, Hiriyakkanavar,Junjappa, Hiriyakkanavar
-
p. 5327 - 5332
(2007/10/02)
-
- STEREOCHEMICAL COURSE OF THE PALLADIUM-CATALYSED ARYLATION OF DISUBSTITUTED ACTIVATED ALKENES WITH BENZOYL CHLORIDE
-
The palladium-catalysed arylation of ten 1,1- and 1,2-disubstituted activated alkenes with benzoyl chloride was studied.In most cases, more than one product was formed.The stereochemical course of the arylation appears to be controlled by the polarity of
- Spencer, Alwyn
-
p. 209 - 216
(2007/10/02)
-
- (Z)‐enol p‐tosylate derived from methyl acetoacetate: A useful cross‐coupling partner for the synthesis of methyl (Z)‐3‐phenyl (or aryl)‐2‐butenoate
-
Procedures yielding (Z)‐3‐(p‐toluenesulfonyloxy)but‐2‐enoate [(Z)‐1] as white prisms and methyl (Z)‐3‐phenyl‐2‐butenoate [(Z)‐2] as a colorless oil are presented. Following are notes on the instruments and chemicals used and required. The chapter conclude
- Ashida, Yuichiro,Nakatsuji, Hidefumi,Tanabe, Yoo
-
-