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

Flow carbonylation of sterically hindered ortho-substituted iodoarenes

• Carl J. Mallia,
• Gary C. Walter and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2016, 12, 1503–1511, doi:10.3762/bjoc.12.147

• fixed 5 mol % of Pd(OAc)2 and 10 mol % of the phosphine ligand was investigated. It was noted that the catalyst level could be reduced [34], but this amount allowed for an efficient catalytic process with short reaction times in the region of two hours, a good match for the flow system assembly [8

• ]. Five different phosphine ligands were subsequently tested, three of which were monodentate with a variable cone angle (6–8; 145–256°) [35][36] and the other two bidendate phosphine ligands namely 1,4-bis(diphenylphosphino)butane (DPPB, 9; βn = 98°) and Xantphos (10; 104 and 133°) with differing bite

• of X-ray structure; C) ball and stick representation of X-ray structure showing the tolyl group only; D) topside view of X-ray structure [18]. Reverse “tube-in-tube” reactor. Phosphine ligands used for the ortho-carbonylation reaction. X-ray structure of substrate 33. Comparison of plug flow reactor

Microwave-assisted synthesis of (aminomethylene)bisphosphine oxides and (aminomethylene)bisphosphonates by a three-component condensation

• Erika Bálint,
• Ádám Tajti,
• Anna Dzielak,
• Gerhard Hägele and
• György Keglevich

Beilstein J. Org. Chem. 2016, 12, 1493–1502, doi:10.3762/bjoc.12.146

• (aminomethylene)bisphosphonates, but in the latter case a secondary phosphine oxide is the P-reagent [33][39]. In addition, (aminomethylene)bisphosphine oxides can be synthesized by the reaction of two molecules of (dialkylamino)(diphenylphosphinoyl)chloromethane (Scheme 4a) [40][41], or by the addition of

Stereodynamic tetrahydrobiisoindole “NU-BIPHEP(O)”s: functionalization, rotational barriers and non-covalent interactions

• Golo Storch,
• Sebastian Pallmann,
• Frank Rominger and
• Oliver Trapp

Beilstein J. Org. Chem. 2016, 12, 1453–1458, doi:10.3762/bjoc.12.141

• preparation of tailor-made functionalized stereodynamic ligands possible and give an outline for possible applications in enantioselective catalysis. Keywords: atropisomer; enantioselective DHPLC; ligand design; non-covalent interactions; Okamoto phases; phosphine ligand; stereodynamic ligands; Introduction

Ring-whizzing in polyene-PtL₂ complexes revisited

• Oluwakemi A. Oloba-Whenu,
• Thomas A. Albright and
• Chirine Soubra-Ghaoui

Beilstein J. Org. Chem. 2016, 12, 1410–1420, doi:10.3762/bjoc.12.135

• is Pt and a phosphine. The second method employs the use of a bidentate phosphine. In this regard we have chosen diphosphinylethane (dpe). This idea here is that the P–Pt–P angle is around 100° in polyene–ML2 complexes. Upon dissociation the 14 electron PtL2 complex strongly prefers to be linear [22

• haptotropic rearrangement of 48 to 53. Notice that passage through the η2 intermediate causes the phosphines to become equivalent. Benn and co-workers [74] in fact observe phosphine equivalence with a barrier of approximately 13 kcal/mol for the naphthalene–Ni(PR3)2 compounds. Our calculations put 54 to be

Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• enatiofacial selectivity, the use of a cyclic imide ensured exclusive formation of the Z-enolate. During optimization, it was found that an N-aryl group containing 2,6-disubstitution was crucial for obtaining high levels of enantioselectivity. Addition of a variety of bis-aryl secondary phosphine oxides

• nitroalkene [67]. α,β-Unsaturated phosphonates and phosphine oxides Transition metal catalysts In 2006, Hayashi and co-workers reported the first conjugate addition–enantioselective protonation of allenes 165 bearing a phosphine oxide (Scheme 39) [68]. Incorporation of the phosphine oxide allowed for

• enantioselective Friedel–Crafts addition of pyrroles to imides 84. Kobayashi’s enantioselective addition of malonates to α-substituted N-acryloyloxazolidinones. Chen and Wu’s enantioselective addition of thiophenol to N-methacryloyl benzamide. Tan’s enantioselective addition of secondary phosphine oxides and

NeoPHOX – a structurally tunable ligand system for asymmetric catalysis

• Jaroslav Padevět,
• Marcus G. Schrems,
• Robin Scheil and
• Andreas Pfaltz

Beilstein J. Org. Chem. 2016, 12, 1185–1195, doi:10.3762/bjoc.12.114

• difficult, literature precedence indicated that the introduction of the phosphine group might be possible by the reaction of a diarylphosphide anion with chloroalkyloxazoline 2. Ashby et al. [20] investigated the reactivity of neopentyl halide systems with various metal diphenylphosphides and found that the

Chiral cyclopentadienylruthenium sulfoxide catalysts for asymmetric redox bicycloisomerization

• Barry M. Trost,
• Michael C. Ryan and
• Meera Rao

Beilstein J. Org. Chem. 2016, 12, 1136–1152, doi:10.3762/bjoc.12.110

• [41] (Figure 1a). The proposed mechanism of this fascinating reaction involves chloride abstraction of the ruthenium catalyst by indium(III) triflate and phosphine ligand dissociation. The propargyl alcohol then coordinates to the now coordinatively unsaturated cyclopentadienylruthenium (CpRu

• phosphine ligand before catalysis can occur (vide supra). In other words, ruthenium must have two open coordination sites in order to bind the substrate. To test if there is a similar requirement for 1, we decided to add one catalyst equivalent of an auxiliary ligand to test its impact on reaction rate

The synthesis of functionalized bridged polycycles via C–H bond insertion

• Jiun-Le Shih,
• Po-An Chen and
• Jeremy A. May

Beilstein J. Org. Chem. 2016, 12, 985–999, doi:10.3762/bjoc.12.97

• oxide oxidant. Notably, a hindered ligand was again necessary for bridged-bicycle formation – in this case the diadamantyl phosphine 106. The Thorpe–Ingold effect was also found to be highly beneficial for the reaction. An interesting mechanistic study using a less selective substrate showed that the

A cross-metathesis approach to novel pantothenamide derivatives

• Jinming Guan,
• Matthew Hachey,
• Lekha Puri,
• Vanessa Howieson,
• Kevin J. Saliba and
• Karine Auclair

Beilstein J. Org. Chem. 2016, 12, 963–968, doi:10.3762/bjoc.12.95

• after dissociation from the metal complex, phosphine ligands can attack the carbine [23]. Thus a phosphine-free catalyst was desirable, and the Hoveyda–Grubbs’ 2nd generation catalyst (4) was chosen. As predicted, the yields increased (Table 1) when catalyst 4 was used for the reaction of 9 with

1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis

• Antonia Mielgo and
• Claudio Palomo

Beilstein J. Org. Chem. 2016, 12, 918–936, doi:10.3762/bjoc.12.90

• of thiazol-4(5H)-ones as pronucleophiles in asymmetric catalytic reactions has been investigated in the Michael addition reaction to nitroalkenes and α-silyloxyenones, phosphine-catalyzed γ-addition to allenoates and alkynoates, α-amination reactions and iridium-catalyzed allylic substitution

• interaction. In addition, adducts 76 and 77 were easily transformed into the corresponding carboxylic acids 79 and 80 by treatment with periodic acid (Scheme 14) and thiolactone 81 by simple ring opening of the latter under mild acidic conditions. Phosphine-catalyzed γ-addition to allenoates and alkynoates

• . Chiral phosphine-mediated nucleophilic catalysis has attracted considerable attention in the recent years [98][99][100][101]. However, few examples of phosphine-mediated γ-addition reactions have been reported. Pioneering studies on γ-additions of pronucleophiles to allenoates or alkynoates were first