Encaging palladium(0) in layered double hydroxide: A sustainable catalyst for solvent-free and ligand-free Heck reaction in a ball mill

• Wei Shi,
• Jingbo Yu,
• Zhijiang Jiang,
• Qiaoling Shao and
• Weike Su

Beilstein J. Org. Chem. 2017, 13, 1661–1668, doi:10.3762/bjoc.13.160

• , which is desirable in the fields of chemistry, materials science, biology, pharmaceutical, dyestuff, agriculture and so forth [8][9][10][11][12]. The homogeneous palladium salts along with phosphine- or nitrogen-based ligands were employed as the traditional catalyst systems not only in solution-based C

Direct catalytic arylation of heteroarenes with meso-bromophenyl-substituted porphyrins

• Alexei N. Kiselev,
• Olga K. Grigorova,
• Alexei D. Averin,
• Sergei A. Syrbu,
• Oskar I. Koifman and
• Irina P. Beletskaya

Beilstein J. Org. Chem. 2017, 13, 1524–1532, doi:10.3762/bjoc.13.152

• partially reduced by the phosphine ligand. The application of another catalytic system with Pd(0), Pd(dba)2/DavePhos (20:22 mol %, dba = dibenzylideneacetone) together with a 100% excess of benzothiazole was more successful as it afforded 32% yield of compound 3 (Table 1, entry 2); it is interesting that

• catalytic conditions proposed by Osuka for the β-arylation of porphyrins with bromoarenes [28] and investigated the reactions of the zinc porphyrinates 1 and 2 with benzoxazole (2 equiv) or benzothiazole (2 equiv) in the presence of Pd(OAc)2 (20 mol %) without phosphine ligand with pivalic acid as an

• without any additional ligand was shown to be advantageous over catalytic systems with phosphine ligands. Osuka also used this approach for β-arylation of porphyrins. In this ligandless reaction the Pd(0) species from palladium acetate could be provided by the traces of amine present in DMA, and the

1-Imidoalkylphosphonium salts with modulated C_α–P⁺ bond strength: synthesis and application as new active α-imidoalkylating agents

• Jakub Adamek,
• Roman Mazurkiewicz,
• Anna Węgrzyk and
• Karol Erfurt

Beilstein J. Org. Chem. 2017, 13, 1446–1455, doi:10.3762/bjoc.13.142

• arenes can be markedly facilitated using 1-imidoalkylphosphonium salts derived from triarylphosphines with electron-withdrawing substituents such as tris(m-chorophenyl)phosphine, tris(p-chlorophenyl)phosphine and tris[p-(trifluoromethyl)phenyl]phosphine. Microwave irradiation also considerably

• salts derived from triarylphosphines with electron-withdrawing substituents such as tris(m-chorophenyl)phosphine, tris(p-chlorophenyl)phosphine and tris[p-(trifluoromethyl)phenyl]phosphine were synthesized and tested in the reaction. As expected, the phosphonium salts with a reduced Cα–P+ bond strength

• reacted with anisole and 1,3-dimethoxybenzene at much lower temperatures (Table 3, entries 3–7, 10, 11, 13, 17–19, 22 and 23). The most clear-cut results were obtained for tris[p-(trifluoromethyl)phenyl]phosphine derivatives. 1-Phthalimidoethyltris[p-(trifluoromethyl)phenyl]phosphonium tetrafluoroborate

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

• A. Michael Downey and
• Michal Hocek

Beilstein J. Org. Chem. 2017, 13, 1239–1279, doi:10.3762/bjoc.13.123

• of difficult-to-remove (especially in the presence of polar, unprotected products) phosphine oxide and second the need to work under anhydrous conditions. However, using stoichiometric conditions the list of glycosides available is now expansive ranging from simple phenolic glycosides to aromatic

• esters to fully unprotected nucleosides. We highlight these examples below. Due to the inherent challenges in both selective reactivity and purification of such polar products in the presence of phosphine oxide, it is not surprising that extensive optimization of conditions was necessary in all cases

• . 5.1.1 Accessing phenolic glycosides: To the best of our knowledge the first example of this methodology was applied to the synthesis of phenolic glycosides by Grynkiewicz [103][104] nearly 40 years ago. In his seminal work he discovered that by using a more reactive phosphine (PBu3), aryl glycosides

Automating multistep flow synthesis: approach and challenges in integrating chemistry, machines and logic

• Chinmay A. Shukla and
• Amol A. Kulkarni

Beilstein J. Org. Chem. 2017, 13, 960–987, doi:10.3762/bjoc.13.97

• -supported phosphine (20 equiv) as the trapping agent. The imine is further hydrogenated at 25 °C and 20 bar pressure by using an H-cube reactor with 10% Pd/C as a catalyst [72]. Trifluoroacetylation of the amine intermediate is then carried out in a chip reactor with trifluoroacetic anhydride (in DCM) as a

• packed bed reactor control strategy will remain identical for all reagent packed reactors. The azide and the aldehyde intermediate can be mixed and preheated at the reaction temperature and passed through a phosphine-functionalized polymer packed bed reactor to obtain the imine intermediate. This imine

Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes

• Carmen Moreno-Marrodan,
• Francesca Liguori and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2017, 13, 734–754, doi:10.3762/bjoc.13.73

• more usual strategy is the so-called “selective poisoning”, i.e., the improvement of the catalyst’s selectivity by the addition of variable, often large, amount of contaminants, either organic ligands (quinolone [65][66], phosphine [67]), carbon monoxide [68], sulfides [69], sulfoxides [70][71] defined

Unpredictable cycloisomerization of 1,11-dien-6-ynes by a common cobalt catalyst

• Abdusalom A. Suleymanov,
• Dmitry V. Vasilyev,
• Valentin V. Novikov,
• Yulia V. Nelyubina and
• Dmitry S. Perekalin

Beilstein J. Org. Chem. 2017, 13, 639–643, doi:10.3762/bjoc.13.62

• cycloisomerization in the presence of the cobalt catalytic system CoBr2/phosphine ligand/Zn/ZnI2 giving cyclohexene, diene or cyclopropane structures depending on the type of the phosphine ligand. This unpredictable behaviour suggests that, although the availability of the cobalt catalytic system is appealing, the

• /phosphine ligand/Zn/ZnI2 for the carbon–carbon bond formation has become a subject of a growing interest (for reviews see [15][16][17][18][19][20][21]). This catalytic system has many advantages, including the availability of the cobalt salts and high tolerance to organic functional groups (for some recent

• examples see [22][23][24][25][26][27]). However, it has been noted that the direction of the catalytic reactions often depends on the structure of the phosphine ligand. Major research on these ligand-controlled reactions has been made by the groups of Hilt and Cheng, in particular, on the selective

Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• only suitable for activated halides having an ortho-nitro substituent; lower yields were observed in the case of unactivated aryl halides, such as 2-isopropylbromobenzene and 2,5-dimethylchlorobenzene. Inspired by a huge effect of the phosphine ligand on the reaction performance, the Beller group

• synthesized a series of novel imidazole-based phosphine ligands, and their effciency was carefully screened [23]. Among these ligands, the one with two isopropyl groups located at the phenyl ring (L3) was effective in converting aryl chlorides and bromides to the corresponding phenols in moderate to excellent

• structural motifs. Hydroxylation of aryl halides using biphenylphosphine as ligand. Hydroxylation of aryl halides using tert-butylphosphine as ligand. Hydroxylation of aryl halides using imidazole typed phosphine ligands. [Pd(cod)(CH2SiMe3)2] catalyzed hydroxylation of aryl halides. Pd/PANI catalyzed

Pd- and Cu-catalyzed approaches in the syntheses of new cholane aminoanthraquinone pincer-like ligands

• Nikolay V. Lukashev,
• Gennadii A. Grabovyi,
• Dmitry A. Erzunov,
• Alexey V. Kazantsev,
• Gennadij V. Latyshev,
• Alexei D. Averin and
• Irina P. Beletskaya.

Beilstein J. Org. Chem. 2017, 13, 564–570, doi:10.3762/bjoc.13.55

• , the addition of an equimolar amount of iPrOH to the mixture of 3a and 6a under the same conditions led to the two-fold decrease in yield of 5c. The replacement of BINAP with other phosphine ligands (t-Bu3P, dppf, PPF-NMe2) gave a very low turnover of Pd catalyst (up to 8 cycles). The increase in

Solid-phase enrichment and analysis of electrophilic natural products

• Frank Wesche,
• Yue He and
• Helge B. Bode

Beilstein J. Org. Chem. 2017, 13, 405–409, doi:10.3762/bjoc.13.43

• dichloromethane. After disulfide-bond cleavage with a solution of tris(2-carboxyethyl)phosphine (TCEP) in a 1:5:10 mixture of phosphate-buffered saline (PBS)/chloroform/methanol at pH 7, the filtrate was analyzed by HPLC–MS. As expected the corresponding mass m/z 493.2 [M + H]+ of the cleaved cycloaddition

Decarboxylative and dehydrative coupling of dienoic acids and pentadienyl alcohols to form 1,3,6,8-tetraenes

• Ghina’a I. Abu Deiab,
• Mohammed H. Al-Huniti,
• I. F. Dempsey Hyatt,
• Emma E. Nagy,
• Kristen E. Gettys,
• Sommayah S. Sayed,
• Christine M. Joliat,
• Paige E. Daniel,
• Rupa M. Vummalaneni,
• Andrew T. Morehead Jr,
• Andrew L. Sargent and
• Mitchell P. Croatt

Beilstein J. Org. Chem. 2017, 13, 384–392, doi:10.3762/bjoc.13.41

• , it was determined that phosphine ligands were necessary (Table 1, entry 11), either as ligands or as participants in the reaction as discussed later. The typical catalyst used, Pd(PPh3)4, worked well, however, it was found that a more ideal ratio of palladium metal to ligand was 1:1 or 1:2, with

• reaction as is discussed mechanistically later (Scheme 3). Similar to the single component reaction, more than two equivalents of phosphine, relative to palladium metal, was detrimental (compare entries 12–14 of Table 1 with entries 6–8 of Table 2), however, the reaction was successful using Pd(PPh3)4

• . Pathway B involves a Morita–Baylis–Hillman type process. The role of water would be to hydrogen bond to the carboxylate to make the system more electrophilic (B). This would accelerate the addition of the phosphine to generate zwitterion C [58]. Preliminary modeling for this ion indicates that both the

Highly bulky and stable geometry-constrained iminopyridines: Synthesis, structure and application in Pd-catalyzed Suzuki coupling of aryl chlorides

• Yi Lai,
• Zhijian Zong,
• Yujie Tang,
• Weimin Mo,
• Nan Sun,
• Baoxiang Hu,
• Zhenlu Shen,
• Liqun Jin,
• Wen-hua Sun and
• Xinquan Hu

Beilstein J. Org. Chem. 2017, 13, 213–221, doi:10.3762/bjoc.13.24

• aryl or alkyl halides include phosphine ligands independently developed by, for example, Buchwald [13][14][15], Hartwig [16][17], Fu [18][19][20], Kwong [21][22][23], Tang [24][25][26][27] and Lundgren [28], and N-heterocyclic carbene ligands due to the inherent strong sigma-donating property [29

The synthesis of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides by the microwave-assisted Pudovik reaction

• Erika Bálint,
• Ádám Tajti,
• Anna Ádám,
• István Csontos,
• Konstantin Karaghiosoff,
• Mátyás Czugler,
• Péter Ábrányi-Balogh and
• György Keglevich

Beilstein J. Org. Chem. 2017, 13, 76–86, doi:10.3762/bjoc.13.10

• -aminophosphonate derivatives embrace the Kabachnik–Fields (phospha-Mannich) three-component condensation, where an amine, an aldehyde or ketone and a >P(O)H reagent, such as a dialkyl phosphite or a secondary phosphine oxide react in a one-pot manner [6][7][8][9][10], and the Pudovik (aza-Pudovik) reaction, in

• the dialkyl phosphite were applied [43][44][45][46][47][48][49][50][51][52]. The synthesis of α-aryl-α-aminophosphine oxides by the addition of secondary phosphine oxides to imines is much less studied. Only a few publications were found and the reported reactions were performed in solvent (in DEE

Iodination of carbohydrate-derived 1,2-oxazines to enantiopure 5-iodo-3,6-dihydro-2H-1,2-oxazines and subsequent palladium-catalyzed cross-coupling reactions

• Michal Medvecký,
• Igor Linder,
• Luise Schefzig,
• Hans-Ulrich Reissig and
• Reinhold Zimmer

Beilstein J. Org. Chem. 2016, 12, 2898–2905, doi:10.3762/bjoc.12.289

• -oxazine syn-11 in 41% yield. Next, we briefly studied 5-iodo-1,2-oxazine syn-4a as substrate in Heck reactions. The substrate was reacted with the alkyl acrylates 12a (R1 = Me) and 12b (R1 = t-Bu) under phosphine-free conditions [33][34] using 6 mol % of palladium(II) acetate, triethylamine as base and

Catalytic Wittig and aza-Wittig reactions

• Zhiqi Lao and
• Patrick H. Toy

Beilstein J. Org. Chem. 2016, 12, 2577–2587, doi:10.3762/bjoc.12.253

• section summarizes how arsenic and tellurium-based catalytic Wittig-type reaction systems were developed first due to the relatively easy reduction of the oxides involved. This is followed by a presentation of the current state of the art regarding phosphine-catalyzed Wittig reactions. The second section

• covers the field of related catalytic aza-Wittig reactions that are catalyzed by both phosphine oxides and phosphines. Keywords: aza-Wittig reactions; catalysis; phosphines; phosphine oxides; reduction; silanes; Wittig reactions; Introduction The Wittig reaction is a venerable transformation for

• inexpensive reagents to generate the necessary phosphonium ylide (phosphorane) reactant (a phosphine, typically Ph3P (1), an alkyl halide and a base), also adds to its appeal [3][4]. However, despite its proven utility, the Wittig reaction suffers from limitations that may deter from its use, especially on a

Protonated paramagnetic redox forms of di-o-quinone bridged with p-phenylene-extended TTF: A EPR spectroscopy study

• Nikolay O. Chalkov,
• Vladimir K. Cherkasov,
• Gleb A. Abakumov,
• Andrey G. Starikov and
• Viacheslav A. Kuropatov

Beilstein J. Org. Chem. 2016, 12, 2450–2456, doi:10.3762/bjoc.12.238

• , should have opposite signs. Considering this, it becomes evident that the averaged value of the coupling constants in (1·)H3 (|0.74−2.28|/2 = 0.77) is in good agreement with the value 0.69 G, which was measured for quintet constant in (1·−)H2. The nature of the phosphine ligand is also important in the

Regiocontroled Pd-catalysed C5-arylation of 3-substituted thiophene derivatives using a bromo-substituent as blocking group

• Mariem Brahim,
• Hamed Ben Ammar,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2016, 12, 2197–2203, doi:10.3762/bjoc.12.210

• introduction of aryl substituents at C5-position via Pd-catalysed direct arylation. With 1 mol % of a phosphine-free Pd catalyst, KOAc as the base and DMA as the solvent and various electron-deficient aryl bromides as aryl sources, C5-(hetero)arylated thiophenes were synthesized in moderate to high yields

• conditions in terms of number of steps, base nature, use of a phosphine-free catalyst at low loading and a quite “atom economic” aryl source promoting such a C5-arylation using C3-substituted 2-bromothiophenes. We report i) that only 1 mol % of air-stable Pd(OAc)2 catalyst associated to KOAc promotes the

• phosphine-free Pd(OAc)2 catalyst performed at 110 °C, only afforded the desired product 1 in a trace amount, but a complete conversion of 2-bromothiophene was observed, revealing the high reactivity of the thienyl C–Br bond under these conditions (Table 1, entry 1). Using a lower reaction temperature of 80

Enantioconvergent catalysis

• Justin T. Mohr,
• Jared T. Moore and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2016, 12, 2038–2045, doi:10.3762/bjoc.12.192

• type I enantioconvergent catalysis was reported by Glueck for the preparation of enantioenriched P-chiral phosphines (Scheme 2) [17]. In this process, enantiopure Pd complex (R,R)-4 reacts with racemic phosphine 3 to form phosphido complexes 5 and 6. Although the rate of configurational inversion of

• enantiopure phosphine catalyst 27 in order to generate the coupled product 30 with both high ee and dr (Scheme 6) [31]. Presumably, the allenyl stereochemistry is destroyed upon 1,4-addition of the phosphine catalyst, resulting in chiral phosphonium adduct 29 that further reacts with deprotonated oxazole 28

Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates

• Maurizio Selva,
• Alvise Perosa,
• Sandro Guidi and
• Lisa Cattelan

Beilstein J. Org. Chem. 2016, 12, 1911–1924, doi:10.3762/bjoc.12.181

• organocatalysts offers several practical advantages: (i) the synthesis of [P8881][CH3OCO2] involves a halide-free methylation of a trialkyl phosphine with nontoxic DMC, (ii) acetate and phenolate salt derivatives could be obtained from [P8881][CH3OCO2] through a chlorine-free metathesis with acetic acid and

Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes

• Michael Nonnenmacher,
• Dominik M. Buck and
• Doris Kunz

Beilstein J. Org. Chem. 2016, 12, 1884–1896, doi:10.3762/bjoc.12.178

• complexes with phosphine ligands [58][59]. Consequently, the signal at 186.3 ppm can be assigned to the trans-CO ligand and that at 183.2 ppm to the cis-CO ligand (relative to NHC). Thus, it is the cis-CO ligand that undergoes a fast CO exchange. The same dynamic behavior is observed for complex 13C2b

• shown to occur by an associative mechanism via a trigonal bipyramidal intermediate [66][67], which was also crystallographically characterized in the case of a cationic Rh complex bearing a bidentate phosphine ligand [68]. Our DFT-calculations for the tricarbonyl complex 3a bearing the dipiy ligand show

Practical synthetic strategies towards lipophilic 6-iodotetrahydroquinolines and -dihydroquinolines

• David R. Chisholm,
• Garr-Layy Zhou,
• Ehmke Pohl,
• Roy Valentine and
• Andrew Whiting

Beilstein J. Org. Chem. 2016, 12, 1851–1862, doi:10.3762/bjoc.12.174

• , phosphine additives and strong heating or microwave conditions in order to effect coupling with most acetylenes. Accordingly, it was anticipated that the aryl iodides would be more versatile due to their greater propensity to undergo oxidative additions. Therefore, in this paper we report herein the

TMSBr-mediated solvent- and work-up-free synthesis of α-2-deoxyglycosides from glycals

• Mei-Yuan Hsu,
• Yi-Pei Liu,
• Sarah Lam,
• Su-Ching Lin and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2016, 12, 1758–1764, doi:10.3762/bjoc.12.164

• ). Furthermore, various phosphine and phosphine oxide reagents were added in O-2-deoxyglycosylation reactions (Table 2, entries 8–11); surprisingly, the desired product 25 exhibited a high yield with excellent α-selectivity (78%, α:β = 10:1, Table 2, entry 11) with TPPO [77]. Encouraged by these results, we

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

A T-shape diphosphinoborane palladium(0) complex

• Patrick Steinhoff and
• Michael E. Tauchert

Beilstein J. Org. Chem. 2016, 12, 1573–1576, doi:10.3762/bjoc.12.152

• material (2-bromophenyl)dicyclohexylphosphine (7) was produced by palladium catalyzed coupling of dicyclohexylphosphine with 1-iodo-2-bromobenzene [15]. Phosphine 7 was lithiated in diethyl ether with n-BuLi [16][17], affording the diethyl ether adduct 8. Reaction of 8 with 0.5 equiv of PhBCl2 in toluene

Dinuclear thiazolylidene copper complex as highly active catalyst for azid–alkyne cycloadditions

• Anne L. Schöffler,
• Ata Makarem,
• Frank Rominger and
• Bernd F. Straub

Beilstein J. Org. Chem. 2016, 12, 1566–1572, doi:10.3762/bjoc.12.151

• group prepared, isolated, and structurally characterized molecular dicopper acetylide complexes, and investigated their reactivity towards azide substrates [36]. For standard CuAAC reactions, copper(I) carboxylates [5][38], mononuclear copper(I) phosphine carboxylate complexes [39] or copper(I) salts