The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

Design and synthesis of quasi-diastereomeric molecules with unchanging central, regenerating axial and switchable helical chirality via cleavage and formation of Ni(II)–O and Ni(II)–N coordination bonds

• Vadim A. Soloshonok,
• José Luis Aceña,
• Hisanori Ueki and
• Jianlin Han

Beilstein J. Org. Chem. 2012, 8, 1920–1928, doi:10.3762/bjoc.8.223

• enolates 16, in the presence of relatively strong bases (KOt-Bu), is an established step in general methods for homologation of the glycine moiety by alkyl halide alkylation [27][50][51][52][53], aldol [29][33][36][37] and Michael [28][31][34][35][38][39][43][44][45][46][47] addition reactions. The

Evaluation of a chiral cubane-based Schiff base ligand in asymmetric catalysis reactions

• Kyle F. Biegasiewicz,
• Michelle L. Ingalsbe,
• Jeffrey D. St. Denis,
• James L. Gleason,
• Junming Ho,
• Michelle L. Coote,
• G. Paul Savage and
• Ronny Priefer

Beilstein J. Org. Chem. 2012, 8, 1814–1818, doi:10.3762/bjoc.8.207

• cyclopropanation and Michael addition reactions. Although there was no increase in stereocontrol, upon computational evaluation using both M06L and B3LYP calculations, it was revealed that a pseudo six-membered ring exists, through H-bonding of a cubyl hydrogen to the copper core. This decreases the steric bulk

• ) toluene complex, as well as Cu(OTf)2; however, we only obtained a maximum value of 12% ee with Cu(OTf) 2 in Et2O (Table 2, entry 10). The use of Et2Zn has also been used to provide excellent stereoselectivity in Michael addition reactions [21][22]. However, with our cubane-based chiral ligand 1 we did not

Organocatalytic tandem Michael addition reactions: A powerful access to the enantioselective synthesis of functionalized chromenes, thiochromenes and 1,2-dihydroquinolines

• Chittaranjan Bhanja,
• Satyaban Jena,
• Sabita Nayak and
• Seetaram Mohapatra

Beilstein J. Org. Chem. 2012, 8, 1668–1694, doi:10.3762/bjoc.8.191

• six membered mono hetero-atom containing, biologically active heterocycles, such as functionalized chromenes (benzopyranes), thiochromenes (thiobenzopyranes) and 1,2-dihydroquinolines, by means of tandem/domino hetero Michael addition reactions, or modified versions [33][34][35][36][37][38], covering

• reactions to access functionalized thiochromenes 2.1. Reactions of 2-mercaptobenzaldehydes with acyclic/cyclic α,β-unsaturated compounds The organocatalytic enantioselective synthesis of chiral thiochromenes through tandem/domino-Michael addition reactions have featured in the literature of the past few

• , and the power of tandem/domino/cascade-Michael addition reactions promoted by chiral organocatalysts has been intensely studied within this field. In this review, we have outlined some significant works concerning the organocatalytic enantioselective Michael addition reaction from three different

Synthesis and evaluation of new guanidine-thiourea organocatalyst for the nitro-Michael reaction: Theoretical studies on mechanism and enantioselectivity

• Tatyana E. Shubina,
• Matthias Freund,
• Sebastian Schenker,
• Timothy Clark and
• Svetlana B. Tsogoeva

Beilstein J. Org. Chem. 2012, 8, 1485–1498, doi:10.3762/bjoc.8.168

• group and that of Jacobsen reported the first successful application of primary amine-thiourea organocatalysts with the synchronous dual activation of a nucleophile and an electrophile in nitro-Michael addition reactions [36][37][38][39][40][41][42]. Bifunctional organocatalysts that contain both a

• -thiourea organocatalyst has been published up until now [50][51][52][53]. This encouraged us to synthesize and investigate the potential of new guanidine-thiourea 7 as organocatalyst for the nitro-Michael addition reactions. Here we report the first results of our investigations, accompanied by quantum

Cation affinity numbers of Lewis bases

• Christoph Lindner,
• Raman Tandon,
• Boris Maryasin,
• Evgeny Larionov and
• Hendrik Zipse

Beilstein J. Org. Chem. 2012, 8, 1406–1442, doi:10.3762/bjoc.8.163

• on this type of process than for the cation addition reactions considered initially. The use of this type of affinity data as the guiding principle in quantitative reactivity studies will thus be restricted to the comparison of structurally and electronically similar systems. For ethyl acrylate

Organocatalytic asymmetric Michael addition of unprotected 3-substituted oxindoles to 1,4-naphthoquinone

• Jin-Sheng Yu,
• Feng Zhou,
• Yun-Lin Liu and
• Jian Zhou

Beilstein J. Org. Chem. 2012, 8, 1360–1365, doi:10.3762/bjoc.8.157

• , together with our efforts in the synthesis of unsymmetric 3,3-diaryloxindoles [29], we try to develop a catalytic asymmetric method to enantioenriched 3,3-diaryloxindoles. In 2007, Jørgensen and coworkers pioneered the organocatalytic asymmetric addition reactions to quinones [30][31] which turned out to

Synthesis of a novel chemotype via sequential metal-catalyzed cycloisomerizations

• Bo Leng,
• Stephanie Chichetti,
• Shun Su,
• Aaron B. Beeler and
• John A. Porco Jr.

Beilstein J. Org. Chem. 2012, 8, 1338–1343, doi:10.3762/bjoc.8.153

• novel polycyclic cyclopropane chemotype. Results and Discussion In an effort to further explore the utility of alkynyl o-benzaldehydes as scaffolds for reaction screening, we designed a focused reaction screen with diynyl benzaldehyde [7] substrate 3. Based on the cycloisomerization/addition reactions

Enantioselective Michael addition of 2-hydroxy-1,4-naphthoquinones to nitroalkenes catalyzed by binaphthyl-derived organocatalysts

• Saet Byeol Woo and
• Dae Young Kim

Beilstein J. Org. Chem. 2012, 8, 699–704, doi:10.3762/bjoc.8.78

• synthesis [12], and intensive research efforts have been directed toward the development of enantioselective catalytic protocols for this reaction [13][14][15]. The organocatalyst-mediated enantioselective conjugate addition reactions, which are both powerful and environmentally friendly, have been

Catalyst-free and solvent-free Michael addition of 1,3-dicarbonyl compounds to nitroalkenes by a grinding method

• Zong-Bo Xie,
• Na Wang,
• Ming-Yu Wu,
• Ting He,
• Zhang-Gao Le and
• Xiao-Qi Yu

Beilstein J. Org. Chem. 2012, 8, 534–538, doi:10.3762/bjoc.8.61

• particularly interesting and challenging as it involves the generation of a wide range of different functionalized products from Michael adducts [21][22][23][24]. In general, Michael addition reactions require basic or acidic catalysts in organic solvents, as well as long reaction times, which may lead to

• as a catalyst in many organic reactions, quartz sand was selected as the suitable grinding aid owing to its low cost and inertness. To the best of our knowledge, this is the first example in which quartz sand has been successfully used as a grinding aid in Michael addition reactions. Next, the same

Intramolecular carbenoid ylide forming reactions of 2-diazo-3-keto-4-phthalimidocarboxylic esters derived from methionine and cysteine

• Marc Enßle,
• Stefan Buck,
• Roland Werz and
• Gerhard Maas

Beilstein J. Org. Chem. 2012, 8, 433–440, doi:10.3762/bjoc.8.49

• undergo inter- and intramolecular formation of N-, O-, S- and other ylides [1][2]. The benefit of these transformations, which are usually performed with rhodium- or copper-based catalysts, is given by subsequent rearrangement or addition reactions of the reactive ylides; several recent reviews [3][4][5

Asymmetric synthesis of quaternary aryl amino acid derivatives via a three-component aryne coupling reaction

• Elizabeth P. Jones,
• Peter Jones,
• Andrew J. P. White and
• Anthony G. M. Barrett

Beilstein J. Org. Chem. 2011, 7, 1570–1576, doi:10.3762/bjoc.7.185

• Arynes are exceptionally versatile reactive intermediates in organic synthesis. Not only are they able to participate in cycloaddition reactions, they also readily undergo addition reactions with nucleophiles, and the resultant aryl anions may be protonated or undergo alternative transformations [1][2][3

Synthesis of fluoranthenes by hydroarylation of alkynes catalyzed by gold(I) or gallium trichloride

• Sergio Pascual,
• Christophe Bour,
• Paula de Mendoza and
• Antonio M. Echavarren

Beilstein J. Org. Chem. 2011, 7, 1520–1525, doi:10.3762/bjoc.7.178

• with high efficiency in a one-pot transformation. The reaction is totally compatible with aryl bromides, which do not undergo subsequent arylation reaction due to the inertness of gold(I) catalysts towards oxidative addition reactions under homogeneous conditions [63][64]. Cationic gold complexes 5 and

Functionalization of heterocyclic compounds using polyfunctional magnesium and zinc reagents

• Paul Knochel,
• Matthias A. Schade,
• Sebastian Bernhardt,
• Georg Manolikakes,
• Albrecht Metzger,
• Fabian M. Piller,
• Christoph J. Rohbogner and
• Marc Mosrin

Beilstein J. Org. Chem. 2011, 7, 1261–1277, doi:10.3762/bjoc.7.147

• addition reactions at temperatures above −30 °C. Quenching of the 4-magnesiated pyrimidine 109 with MeSO2SMe provides the thiomethyl derivative 110 in 81% yield (Scheme 18 and Supporting Information File 1, Procedure 7) [46]. The presence of a thiomethyl substituent considerably increases the electron

• has been shown to be of radical nature, and it affords the cross-coupling products in very short reaction times, often less than 5 min. 4 MgCl2-Enhanced reactivity of functionalized organozincs towards their addition to aldehydes, ketones and carbon dioxide The addition reactions of organometallic

• transition metal salts and in a very limited scope. Recently, we showed that the cheap and non-toxic main group Lewis acid MgCl2 allows smooth addition reactions of different aromatic, heteroaromatic, alkyl and benzylic zinc reagents to various carbonyl derivatives and carbon dioxide without the use of polar

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• ]. Furthermore, the rapid growing area of tandem reactions has allowed chemists to assemble diverse complex molecular frameworks more conveniently. Although various research efforts have led to gold-catalyzed addition reactions, the area of asymmetric addition has only recently been pioneered. Currently, a broad

• (Scheme 59) [174]. The first step is supposed to be an intramolecular addition of the hydroxy group to the internal carbon of the triple bond, which is similar to the mechanism mentioned above [161][163]. 6 Gold-catalyzed asymmetric addition reactions The chiral ligand used for the transition metal

• -catalyzed reactions are the main determinant of enantioselectivity. Although asymmetric catalysis using chiral organometal complexes and chiral organomolecules have shown many advantages and a range of catalytic asymmetric reactions have been well documented [175], gold-catalyzed asymmetric addition

Alkene selenenylation: A comprehensive analysis of relative reactivities, stereochemistry and asymmetric induction, and their comparisons with sulfenylation

• Vadim A. Soloshonok and
• Donna J. Nelson

Beilstein J. Org. Chem. 2011, 7, 744–758, doi:10.3762/bjoc.7.85

• , and comparison with that of alkene sulfenylation. Alkyl group branching α to the double bond was shown to have the greatest effect on alkene reactivity and the stereochemical outcome of corresponding addition reactions. This is in sharp contrast with other additions to alkenes, which depend more on

• the role of a small amount of MeOH added to the reaction, including stabilization of the intermediate seleniranium ion [41] or its ion pair [64], as well as enabling a different reactive species, such as ArSeOMe [29]. The mechanism of these addition reactions is further complicated by noticeable

• rates of various addition reactions to alkenes. It should be noted that alkene HOMO energy calculations are particularly beneficial as the experimental IE data are usually incomplete or difficult to obtain. In particular, in the present study IE values for some di- and tri-substituted alkenes (Table 1

Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

• Fabian Pfrengle and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 75, doi:10.3762/bjoc.6.75

• cyclohexylidene-substituted dihydropyran cis-5d afforded α-bromo ketone 17 which, upon treatment with NaBH4, produced epoxypyran 18 (Scheme 8). Epoxide 18 was obtained as a single diastereomer and should be a promising substrate for subsequent nucleophilic addition reactions leading to another series of

Solvent-free phase-vanishing reactions with PTFE (Teflon^®) as a phase screen

• Kevin Pels and
• Veljko Dragojlovic

Beilstein J. Org. Chem. 2009, 5, No. 75, doi:10.3762/bjoc.5.75

• reaction apparatus, b) reaction mixture (note a thin stream of bromine vapors flowing straight down), c) bromination was completed when the color of bromine vapors persisted, d) after a work-up tube was inserted bromine vapors were consumed. Bromination of stilbenes. Addition reactions of bromine under

Facile synthesis of two diastereomeric indolizidines corresponding to the postulated structure of alkaloid 5,9E- 259B from a Bufonid toad (Melanophryniscus)

• Angela Nelson,
• H. Martin Garraffo,
• Thomas F. Spande,
• John W. Daly and
• Paul J. Stevenson

Beilstein J. Org. Chem. 2008, 4, No. 6, doi:10.1186/1860-5397-4-6

• was produced with the isomer corresponding to 6 (Scheme 1) predominating. We have previously shown [45], and there is also good literature precedent [46][47], that in indolizidines with unsaturation at C7-C8 there is a tendency for the addition reactions to occur on the concave face, although this

N-1 regioselective Michael- type addition of 5-substituted uracils to (2-hydroxyethyl) acrylate

• Sławomir Boncel,
• Dominika Osyda and
• Krzysztof Z. Walczak

Beilstein J. Org. Chem. 2007, 3, No. 40, doi:10.1186/1860-5397-3-40

• available, and 5-isobutyrylaminouracil was synthesized as reported previously.[14] Commercially available HEA was applied as the Michael acceptor (Scheme 1). Triethylamine (TEA) (1 equivalent) served as a deprotonating agent. The addition reactions were performed in polar aprotic solvents such as DMF or

Vinylogous Mukaiyama aldol reactions with 4-oxy-2-trimethylsilyloxypyrroles: relevance to castanospermine synthesis

• Roger Hunter,
• Sophie C. M. Rees-Jones and
• Hong Su

Beilstein J. Org. Chem. 2007, 3, No. 38, doi:10.1186/1860-5397-3-38

• reagent of choice for promoting extended (vinylogous) Mukaiyama addition reactions to aldehydes,[4] imines [5] and conjugatively to enones [6][7] under Lewis-acid mediated dissociative reaction conditions. Many of these reactions reveal high diastereoselectivities, which has been exploited to access a

Multiple hydride reduction pathways in isoflavonoids

• Auli K. Salakka,
• Tuija H. Jokela and
• Kristiina Wähälä

Beilstein J. Org. Chem. 2006, 2, No. 16, doi:10.1186/1860-5397-2-16

• ). We have discussed a possible mechanism to explain these hydroxyl-dependent divergent pathways [43]. To summarize, all hydride addition reactions with isoflavones appear to involve an initial 1,4-addition to give the isoflavanone enolate. In a hydroxylic solvent, or even on workup under basic