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