Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

• Thilo Focken and
• Stephen Hanessian

Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195

• carbanions with alkyl halides gives stereoselective access to a variety of α-substituted alkylphosphonic acids (Scheme 3). The attack on the alkyl halide occurs from the “left cleft” side of the anion 29 in the (R,R)-isomer. Thus, α-substituted phosphonamides 32 can be obtained in good to excellent

Syntheses of fluorooxindole and 2-fluoro-2-arylacetic acid derivatives from diethyl 2-fluoromalonate ester

• Antal Harsanyi,
• Graham Sandford,
• Dmitri S. Yufit and
• Judith A.K. Howard

Beilstein J. Org. Chem. 2014, 10, 1213–1219, doi:10.3762/bjoc.10.119

• elemental fluorine for the key construction of the carbon–fluorine bond by complementary direct selective direct fluorination [41][42][43][44], continuous flow [45][46][47][48][49] and building block [50] strategies, in this paper, we describe nucleophilic aromatic substitution reactions of carbanions

• ][58][59][60][61][62] or DAST [63] providing an indication of the importance of fluorooxindoles for medicinal chemistry applications. Results and Discussion Reactions of carbanions generated by the addition of sodium hydride to a solution of diethyl 2-fluoromalonate (1) in DMF with ortho

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• (enamines and carbanions) or be involved in cycloaddition reactions affording tricyclic compounds by cascade processes. An unprecedented, co-catalyzed reaction involving enamines 51 as nucleophilic partners, also yields the H-pyrazolo[5,1-a]isoquinoline nucleus 48, in the presence of silver triflate and

Synthesis and quantitative structure–activity relationship study of substituted imidazophosphor ester based tetrazolo[1,5-b]pyridazines as antinociceptive/anti-inflammatory agents

• Wafaa M. Abdou,
• Neven A. Ganoub and
• Eman Sabry

Beilstein J. Org. Chem. 2013, 9, 1730–1736, doi:10.3762/bjoc.9.199

• , showed a notable antinociceptive and anti-inflammatory activity without toxic side-effects. Keywords: antinociceptive/anti-inflammatory agents; imidazophosphor esters; phosphonyl carbanions; ring closure; tetrazolo[1,5-b]pyridazine; Introduction Inflammation is a characteristic feature of disease

Organocatalytic asymmetric selenofunctionalization of tryptamine for the synthesis of hexahydropyrrolo[2,3-b]indole derivatives

• Qiang Wei,
• Ya-Yi Wang,
• Yu-Liu Du and
• Liu-Zhu Gong

Beilstein J. Org. Chem. 2013, 9, 1559–1564, doi:10.3762/bjoc.9.177

• products; selenofunctionalization; Introduction Selenofunctionalization of carbon–carbon double bonds provides practicable opportunities for rapid construction of molecule complexity [1][2][3][4][5][6][7][8], because the versatile carbon–selenium bond could either stabilize carbanions [9][10], serve as a

A study on electrospray mass spectrometry of fullerenol C₆₀(OH)₂₄

• Mihaela Silion,
• Andrei Dascalu,
• Mariana Pinteala,
• Bogdan C. Simionescu and
• Cezar Ungurenasu

Beilstein J. Org. Chem. 2013, 9, 1285–1295, doi:10.3762/bjoc.9.145

• anions formed by electron addition to a fullerenyl radical shall be described as fullerene carbanions and referred to as fullerenide anions (M3 in Scheme 1) and [mM + ne]m–n∙ shall be described as molecular anions. As regards to the observation of distonic fullerenyl-fullerenate M7 ions, such distonic

Easy and direct conversion of tosylates and mesylates into nitroalkanes

• Alessandro Palmieri,
• Serena Gabrielli and
• Roberto Ballini

Beilstein J. Org. Chem. 2013, 9, 533–536, doi:10.3762/bjoc.9.58

• electron-withdrawing effect of the nitro group, nitroalkanes are prone to afford, under basic conditions, stabilized carbanions, which are commonly used as nucleophiles with a variety of electrophiles [8][9][10][11] leading to carbon–carbon bond formation. Furthermore, by making use of the possibility to

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

• are summarized under this title, whether they involve carbocations or carbanions, or “only” polarized intermediates, ionic reactions involving 2 and its derivatives have only been studied to a limited extent so far. And this situation does not change very much if we include the chemical behavior of

• 1.2) [74][75][76] can probably also be exploited to introduce other substituents than TMS. Thus the quenching of the corresponding carbanions with, e.g., carbon dioxide to produce carboxylic acid derivatives of conjugated bisallenes could be tried [83][138][144]. 2. Acyclic nonconjugated bisallenes

A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• of magnitude corresponding to relative reaction times from nanoseconds to 1015 years, we have been able to compare nucleophiles of widely differing structure and reactivity [4]. As illustrated by Figure 1, this method allows us to characterize strong nucleophiles, such as carbanions and ylides, by

• reactions with C-nucleophiles, mostly stabilized carbanions [4][73][74][75][76][77][78][79][80]. As illustrated in Figure 19, the benzhydrylium methodology was again employed for the determination of the nucleophilicities of enamines. Whereas the enamine 32b, which is derived from the diphenylprolinol silyl

Highly selective synthesis of (E)-alkenyl-(pentafluorosulfanyl)benzenes through Horner–Wadsworth–Emmons reaction

• George Iakobson and
• Petr Beier

Beilstein J. Org. Chem. 2012, 8, 1185–1190, doi:10.3762/bjoc.8.131

• . In contrast to most of the reactions with 3, phosphonate 4 gave exclusively E-isomers of 6 (Table 3). This improved selectivity can be explained by relative differences in the stabilities and reactivities of carbanions derived from phosphonates and reactive intermediates. In reactions of phosphoryl

• -stabilized carbanions with aldehydes, several intermediates are formed reversibly. Less-hindered intermediates A and A’, which eliminate to E-alkene, exist in equilibrium with more-hindered intermediates B and B’ giving Z-alkene (Scheme 2). In our reactions, the stabilization of the negative charge in the

Synthesis and structure of tricarbonyl(η⁶-arene)chromium complexes of phenyl and benzyl D-glycopyranosides

• Thomas Ziegler and
• Ulrich Heber

Beilstein J. Org. Chem. 2012, 8, 1059–1070, doi:10.3762/bjoc.8.118

• to the fact that the tricarbonylchromium ligand stabilizes both benzylic and homo-benzylic carbenium ions and carbanions [5][6]. Asymmetric ortho- or meta-substituted tricarbonyl(η6-arene)chromium compounds display planar chirality, which, in turn, makes these chiral complexes attractive catalysts

Fluorescent hexaaryl- and hexa-heteroaryl[3]radialenes: Synthesis, structures, and properties

• Antonio Avellaneda,
• Courtney A. Hollis,
• Xin He and
• Christopher J. Sumby

Beilstein J. Org. Chem. 2012, 8, 71–80, doi:10.3762/bjoc.8.7

• ][11][12]. Derivatives of [3]radialene containing aryl and heteroaryl moieties have gained more interest than the parent compound itself due to their increased stability. The preparation of hexaaryl[3]radialenes, using Fukunaga’s method of reacting stabilised carbanions with tetrachlorocyclopropene [13

• difference in yields between 2 and hexakis(4-cyanophenyl)[3]radialene, 73% reported by Oda [15], is a consequence of the relative stability of the carbanions of the two dicyanodiphenylmethane precursors. To maintain a high yielding synthesis whilst investigating the substitution in the 3-position, a new

• been shown to undergo two one-electron reductions to yield the radical anion and dianion species [1]. In this context, in materials science [1][39][40], there is considerable interest in the use of the carbanions obtained by reduction. Up to now, the most electron deficient hexaaryl[3]radialene

On the control of secondary carbanion structure utilising ligand effects during directed metallation

• Andrew E. H. Wheatley,
• Jonathan Clayden,
• Ian H. Hillier,
• Alison Campbell Smith,
• Mark A. Vincent,
• Laurence J. Taylor and
• Joanna Haywood

Beilstein J. Org. Chem. 2012, 8, 50–60, doi:10.3762/bjoc.8.5

• deprotonation on electronic grounds [1][2]. Moreover, steric effects have also been found to play an important role. Hence, whereas the formation of primary [18] and secondary [19] carbanions through lateral deprotonation has been known for many years, it is only very recently that the analogous formation of

• tertiary carbanions has been reported [20]. Amongst the most important, versatile and widely used agents for directing the deprotonative lithiation of aromatic substrates are amide type (or “N+O”) groups [3]. In the case of such systems, solid-state structural evidence for carbanion structure has only

• -position is not blocked (contrast this scenario with the conversion of 4-H into 4-Lil·3THF) recently led us to examine the hitherto unachievable formation of tertiary carbanions by directed lateral lithiation [16][17]. Accordingly, 2-isopropyl-N,N-diisopropylbenzamide (5-H) has been used to source 5-Lil·L

Selectivity in C-alkylation of dianions of protected 6-methyluridine

• Ngoc Hoa Nguyen,
• Christophe Len,
• Anne-Sophie Castanet and
• Jacques Mortier

Beilstein J. Org. Chem. 2011, 7, 1228–1233, doi:10.3762/bjoc.7.143

• do not alkylate, or give poor yields, with any halides other than iodomethane [21][22][23][24]. Competing base-induced elimination reactions are presumably observed with iodoethane and higher homologues [19][20][25][26]. It has also been proposed that poor reactivity of lithiated carbanions toward

Asymmetric synthesis of tertiary thiols and thioethers

• Jonathan Clayden and
• Paul MacLellan

Beilstein J. Org. Chem. 2011, 7, 582–595, doi:10.3762/bjoc.7.68

• about the C–S, Se or Te bond [62]. Simple inversion in α-thio-substituted carbanions has a barrier as low as 0.5 kcal·mol−1 [63] making inversion itself unlikely to comprise the rate determining step of the racemisation. Consistent with this explanation, the barrier to racemisation increases with

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

• Vladimir N. Boiko

Beilstein J. Org. Chem. 2010, 6, 880–921, doi:10.3762/bjoc.6.88

• have appeared which make use of novel intermediates. Thus, single-electron oxidation or reduction enables the generation of perfluoroalkyl radicals. Two-electron reduction of perfluoroalkyl iodides generates perfluoroalkyl carbanions, which may be stabilized by organophosphorus and organosilicon

• analogues continues to grow. Previous reviews in this area are either dated [19] or focus on specialist aspects such as perfluoroalkyl radicals [20][21][22], fluorinated carbanions [23], organometallic compounds [24][25], perfluoroalkyl sulfenyl halides [26], perfluoroalkyl silicon reagents [27][28][29][30

Shelf-stable electrophilic trifluoromethylating reagents: A brief historical perspective

• Norio Shibata,
• Andrej Matsnev and
• Dominique Cahard

Beilstein J. Org. Chem. 2010, 6, No. 65, doi:10.3762/bjoc.6.65

• Daikin laboratories in 2003. 1-Oxo-1-trifluoromethyl-1λ6-benzo[d]isothiazol-3-one (30), and 1-trifluoromethyl-benzo[1,3,2]dithiazole 1,3,3-trioxide (31) as well as acyclic sulfoximines 32 were synthesized as new trifluoromethylating agents (Scheme 26). It was possible to trifluoromethylate carbanions

Fused bicyclic piperidines and dihydropyridines by dearomatising cyclisation of the enolates of nicotinyl-substituted esters and ketones

• Heloise Brice,
• Jonathan Clayden and
• Stuart D. Hamilton

Beilstein J. Org. Chem. 2010, 6, No. 22, doi:10.3762/bjoc.6.22

• and new reactivity from simple, readily made starting materials. We have used cyclisations of benzamide-stabilised carbanions, for example, to give bicyclic functionalised indolinones as intermediates in the synthesis of the neuroactive amino acids [22][23][24][25][26][27][28][29][30][31][32], while

• related cyclisations of pyridyl-, nicotinamide- and isonicotinamide-containing carbanions yield related bicyclic dihydropyridines [33][34]. While reactive carbanions derived from allyl or benzyllithiums will undergo dearomatising addition even into relatively electron rich rings [35][36][37][38], the

The role of an aromatic group in remote chiral induction during conjugate addition of α-sulfonylallylic carbanions to ethyl crotonate

• Shlomo Levinger,
• Ranjeet Nair and
• Alfred Hassner

Beilstein J. Org. Chem. 2008, 4, No. 32, doi:10.3762/bjoc.4.32

• Shlomo Levinger Ranjeet Nair Alfred Hassner Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel 10.3762/bjoc.4.32 Abstract The impact of a remote aromatic nucleus on the stereochemical outcome of the conjugate addition of α-sulfonylallylic carbanions to an α,β-unsaturated ester

• -(phenylsulfonyl)allylic carbanions bearing a chiral auxiliary [1]. Transmission of asymmetry, though four atoms removed, was striking and was found to depend on the presence of an aromatic nucleus bound to the stereogenic center attached to N in 1. Thus, addition to crotonate 2 of the lithio derivative of amino

• -sulfonylallylic carbanions to open-chain α,β-unsaturated esters, which has been shown to proceed anti-diastereoselectively [2][13] and with the N(1)R*,3S*,4R* relative configuration predominating [1], we assign our major and minor products structures 3 and 4 respectively (showing in Scheme 1 only one enantiomer

Efficient 1,4-addition of α-substituted fluoro(phenylsulfonyl)methane derivatives to α,β-unsaturated compounds

• G. K. Surya Prakash,
• Xiaoming Zhao,
• Sujith Chacko,
• Fang Wang,
• Habiba Vaghoo and
• George A. Olah

Beilstein J. Org. Chem. 2008, 4, No. 17, doi:10.3762/bjoc.4.17

• monofluoromethylated compounds, which would undergo various transformations. New synthetic methods for the synthesis of α-substituted fluoro(phenylsulfonyl)methane derivatives under mild reaction conditions, using convenient starting materials, are still desirable. Fluorinated carbanions are in principle "hard