Inter- and intramolecular enantioselective carbolithiation reactions

• Asier Gómez-SanJuan,
• Nuria Sotomayor and
• Esther Lete

Beilstein J. Org. Chem. 2013, 9, 313–322, doi:10.3762/bjoc.9.36

• concept to avoid the epimerization of reactive intermediates, which has allowed them to carry out the enantioselective version of the above procedure. Thus, the use of a flow microreactor system has allowed the enantioselective carbolithiation of conjugated enynes, followed by the reaction with

• intermediates that can be converted into various types of chiral ferrocene derivatives through diastereoselective ortho-lithiation [21]. Some years ago, the concept of flash chemistry was proposed, involving fast chemical synthesis by using flow microreactors, which enabled the use of highly reactive

• intermediates before they decompose [22][23][24][25]. Thus, Yoshida [26] demonstrated that the addition of aryllithiums, generated by halogen–lithium exchange, to conjugated enynes bearing an appropriate directing group occurs with complete regioselectivity and in good yields. More recently, they applied this

Presence or absence of a novel charge-transfer complex in the base-catalyzed hydrolysis of N-ethylbenzamide or ethyl benzoate

• Shinichi Yamabe,
• Wei Guan and
• Shigeyoshi Sakaki

Beilstein J. Org. Chem. 2013, 9, 185–196, doi:10.3762/bjoc.9.22

• minimal model of TS1 was proposed and was found to be insensitive to n. Keywords: basic hydrolyses; DFT calculations; ethyl benzoate; N-ethylbenzamide; reactive intermediates; transition states; Introduction Basic hydrolyses of esters and amides have been extensively studied experimentally [1]. Use of

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

• bisallenes 4.2.3 Exocyclic bisallenes Bisallenes as reactive intermediates Bisallenes with heteroatoms in their tethers (heteroorganic bisallenes) 6.1 Thermally induced reactions of heteroorganic bisallenes 6.2 Transition metal-induced reactions of heteroorganic bisallenes Conclusion Acknowledgements

Photoreactions of cyclic sulfite esters: Evidence for diradical intermediates

• Rick C. White,
• Benny E. Arney Jr. and
• Heiko Ihmels

Beilstein J. Org. Chem. 2012, 8, 1208–1212, doi:10.3762/bjoc.8.134

• studies have revealed information on reactive intermediates, solvent effects, and stereochemical outcomes, while synthetic work has pointed to novel approaches for preparing various molecules. For example, deazetation reactions in solvents of increasing viscosity were employed to determine whether the

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

• )-(pentafluorosulfanyl)anilines, and the formation of (E)-1-alkenyl-4-(pentafluorosulfanyl)benzenes was demonstrated from diethyl 4-(pentafluorosulfanyl)benzylphosphonates. Proposed synthesis of alkenyl-(pentafluorosulfanyl)benzenes. Reactive intermediates involved in HWE reactions to alkenes 5 and 6. Diazotization

Synthesis of functionalized macrocyclic derivatives of trioxabicyclo[3.3.0]nonadiene

• Sabine Leber,
• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2012, 8, 738–743, doi:10.3762/bjoc.8.83

• with the bisdioxine unit has also been achieved recently [6]. Some of these materials exhibit pronounced complexation of metal ions, such as Cs+, Hg2+, Cu2+, Ag+, and Au3+ [5][6][7]. It may also be possible to stabilize reactive intermediates and unusual functional groups in the concave interiors of

Aryl nitrile oxide cycloaddition reactions in the presence of pinacol boronic acid ester

• Sarah L. Harding,
• Sebastian M. Marcuccio and
• G. Paul Savage

Beilstein J. Org. Chem. 2012, 8, 606–612, doi:10.3762/bjoc.8.67

• other 1,3-disubstituted compounds, through N–O bond cleavage [20]. Nitrile oxides are reactive intermediates that are usually generated in situ and react immediately with the dipolarophile. There have been many methods reported for the generation of nitrile oxides, but the most common one for alkyl

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

• . It is therefore interesting to gather information about the chemoselectivity of these reactive intermediates. For intramolecular reactions, the ring size of the products can make an additional contribution to the observed chemoselectivity. In this study, we have addressed the competition between two

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

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• intermediates that undergo subsequent intermolecular annulations with diverse partners. For example, in 2008, L. Zhang and coworkers demonstrated that a series of 1-(1-alkynyl)cyclopropyl ketones 8, previously used by Schmalz for the synthesis of furans [44], can be used as precursors of reactive intermediates

• = Me, R3 = H, X = C(CO2Me)2). These examples clearly demonstrate the possibility of modulating the electronic properties of reactive intermediates generated upon activation of allenes with Au(I) complexes, and thereby influence the reaction outcome. The development of intermolecular variants of gold

Homocoupling of aryl halides in flow: Space integration of lithiation and FeCl₃ promoted homocoupling

• Aiichiro Nagaki,
• Yuki Uesugi,
• Yutaka Tomida and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2011, 7, 1064–1069, doi:10.3762/bjoc.7.122

• could also be applied to less stable aryllithium compounds that decompose very quickly. One of the major benefits of flow microreactor synthesis is the ability to use highly unstable reactive intermediates. Such intermediates can be rapidly generated and transferred to another location to be used in a

Chemistry in flow systems II

• Andreas Kirschning

Beilstein J. Org. Chem. 2011, 7, 1046–1047, doi:10.3762/bjoc.7.119

• highlight three areas. First of all, we have the application to photochemistry, which has the chance of experiencing a renaissance particularly in an industrial environment. Second, flow chemistry lends itself naturally to the synthesis and direct application of reactive intermediates or reactive reagents

When gold can do what iodine cannot do: A critical comparison

• Sara Hummel and
• Stefan F. Kirsch

Beilstein J. Org. Chem. 2011, 7, 847–859, doi:10.3762/bjoc.7.97

• presence of electrophilic iodine. The reader will also realize how gold-catalyzed processes, which mechanistically benefit from the carbenoid character [55][56][57][58] of the reactive intermediates, cannot be matched by electrophilic processes. As highlighted in the discussion, a starting substrate can be

Homoallylic amines by reductive inter- and intramolecular coupling of allenes and nitriles

• Peter Wipf and
• Marija D. Manojlovic

Beilstein J. Org. Chem. 2011, 7, 824–830, doi:10.3762/bjoc.7.94

• addition of zirconocene hydrochloride (Cp2Zr(H)Cl, Schwartz’s reagent) to π-bonds usually leads predominantly to σ-complexes, and the resulting organozirconocene complexes are valuable reactive intermediates for the formation of carbon–halogen and carbon–carbon bonds [1][2][3][4][5][6]. The reaction of

• reagents that could potentially serve as dianion equivalents and provide (E)-vinylsilanes and (E)-vinylstannanes in good yields [15]. N-Metalloimines are reactive intermediates that represent masked imine derivatives of ammonia, which are often unstable and difficult to prepare. A common method for the

Molecular rearrangements of superelectrophiles

• Douglas A. Klumpp

Beilstein J. Org. Chem. 2011, 7, 346–363, doi:10.3762/bjoc.7.45

• reactive intermediates may also undergo a wide variety of rearrangement-type reactions. Superelectrophilic rearrangements are often driven by charge–charge repulsive effects, as these densely charged ions react so as to maximize the distances between charge centers. These rearrangements involve reaction

Anion–π interactions influence pK_a values

• Christopher J. Cadman and
• Anna K. Croft

Beilstein J. Org. Chem. 2011, 7, 320–328, doi:10.3762/bjoc.7.42

• Supporting Information File 1. Discussion Intermolecular effects on molecules are widely recognised as being important in both binding and reactions, with solvent effects being the classic example of the latter. The effects of solvation on reactive intermediates can change the outcome of a reaction

EPR and pulsed ENDOR study of intermediates from reactions of aromatic azides with group 13 metal trichlorides

• Giorgio Bencivenni,
• Riccardo Cesari,
• Daniele Nanni,
• Hassane El Mkami and
• John C. Walton

Beilstein J. Org. Chem. 2010, 6, 713–725, doi:10.3762/bjoc.6.84

• ], and δ-azidoesters and chlorides into allylated nitrogen heterocycles [30]. To help in elucidating the mechanisms of these reductions, we used CW EPR spectroscopy and attempted to characterise the reactive intermediates in selected reactions involving gallium trichloride. Surprisingly, we found that

CAAC Boranes. Synthesis and characterization of cyclic (alkyl) (amino) carbene borane complexes from BF₃ and BH₃

• Julien Monot,
• Louis Fensterbank,
• Max Malacria,
• Emmanuel Lacôte,
• Steven J. Geib and
• Dennis P. Curran

Beilstein J. Org. Chem. 2010, 6, 709–712, doi:10.3762/bjoc.6.82

• beginning to be used as synthetic reagents, with applications in radical [5][6][7][8][9], ionic [10][11] and organometallic [12] reactions. They are also precursors for making higher complexes with unusual bonding patterns such as boron–boron double bonds [3], or for making unusual reactive intermediates on

Gold film- catalysed benzannulation by Microwave- Assisted, Continuous Flow Organic Synthesis (MACOS)

• Gjergji Shore,
• Michael Tsimerman and
• Michael G. Organ

Beilstein J. Org. Chem. 2009, 5, No. 35, doi:10.3762/bjoc.5.35

• traditional batch-reactor technology [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Independent inlet streams allow reactive intermediates to be kept separate until brought together in miniscule amounts to react immediately; this rapidly depletes the starting materials and