Meta-metallation of N,N-dimethylaniline: Contrasting direct sodium-mediated zincation with indirect sodiation-dialkylzinc co-complexation

• David R. Armstrong,
• Liam Balloch,
• Eva Hevia,
• Alan R. Kennedy,
• Robert E. Mulvey,
• Charles T. O'Hara and
• Stuart D. Robertson

Beilstein J. Org. Chem. 2011, 7, 1234–1248, doi:10.3762/bjoc.7.144

• dialkyl(aryl) sodium zincate ((TMEDA)Na(o-C6H4-NMe2)t-BuZnt-Bu), reminiscent of the lithium congeners ((THF)3Li(o-C6H4-OMe)t-BuZnt-Bu) and ((PMDETA)Li(o-C6H4-OMe)t-BuZnt-Bu) prepared by co-complexation reactions of lithiated anisole with t-Bu2Zn and the relevant Lewis base [27]. The metallation

The allylic chalcogen effect in olefin metathesis

• Yuya A. Lin and
• Benjamin G. Davis

Beilstein J. Org. Chem. 2010, 6, 1219–1228, doi:10.3762/bjoc.6.140

• is likely due to the soft nature of sulfur as a Lewis base making it a better ligand for ruthenium than the oxygen atom in Hoveyda–Grubbs second-generation catalyst 4. It is currently unclear whether a similar effect would be observed for phosphine-containing metathesis catalysts such as 1a and 2. As

Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate

• Michael North and
• Marta Omedes-Pujol

Beilstein J. Org. Chem. 2010, 6, 1043–1055, doi:10.3762/bjoc.6.119

• that Lewis base catalysis made a much greater contribution to the overall catalytic activity of VO(salen)NCS in propylene carbonate than in dichloromethane. Keywords: cyanohydrin; Hammett; kinetics; propylene carbonate; vanadium; Introduction The last 15 years have witnessed an explosion of activity

• Lewis base catalysis are known to be involved in the catalytic cycle, the latter possibly involving the isothiocyanate counterion [52]. Despite their many favourable properties, there is one drawback associated with catalysts 1 and 2; they exhibit highest activity and highest enantioselectivity in

• , which allow differences in the relative importance of Lewis acid and Lewis base catalysis between reactions carried out in dichloromethane and propylene carbonate to be elucidated. Results and Discussion Synthetic Studies Initially, the compatibility of catalysts 1 and 2 with propylene carbonate was

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

• halide to the starting azide should produce the Lewis base–acid adduct 12 that could undergo reduction by ET from more azide to afford, after nitrogen loss, the metal-coordinated aminyl radical 13 together with the ArN3+• radical cation. Aminyl radical 13 could then abstract an H-atom from solvent RH (or

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

• formed in situ according to 1H and 11B NMR analysis, but did not survive the workup conditions. These results set the stage for further studies of the chemistry of CAAC boranes. Keywords: borane Lewis acid Lewis base complexes; carbene–borane complexes; cyclic (alkyl) (amino) carbenes; N-heterocyclic

• carbenes; stable carbenes; Introduction Lewis acid/Lewis base complexes of N-heterocyclic carbenes and boranes (NHC–boranes) are readily prepared from NHC’s and boranes by direct complexation [1][2][3][4]. Unlike many other classes of Lewis base complexes of boranes with neutral molecules (ethers

The subtle balance of weak supramolecular interactions: The hierarchy of halogen and hydrogen bonds in haloanilinium and halopyridinium salts

• Kari Raatikainen,
• Massimo Cametti and
• Kari Rissanen

Beilstein J. Org. Chem. 2010, 6, No. 4, doi:10.3762/bjoc.6.4

• (Lewis base, nucleophilic) [20]. According to this definition, halogen bonding covers a vast family of non-covalent interactions, and a very wide range of interaction energies [20]. Concurrently with the development of practical applications and experimental studies on halogen bonding systems

Diastereoselective functionalisation of benzo-annulated bicyclic sultams: Application for the synthesis of cis-2,4-diarylpyrrolidines

• Susan Kelleher,
• Pierre-Yves Quesne and
• Paul Evans

Beilstein J. Org. Chem. 2009, 5, No. 69, doi:10.3762/bjoc.5.69

• mechanism of stabilisation has been suggested in which one of the sulfonyl oxygen atoms may act as a Lewis base and in doing so stabilise the positive charge [22][23]. Inspection of the X-ray structure obtained for compounds 7a and 7b (not shown) indicates that this stabilisation mechanism may be possible

Continuous flow enantioselective arylation of aldehydes with ArZnEt using triarylboroxins as the ultimate source of aryl groups

• Julien Rolland,
• Xacobe C. Cambeiro,
• Carles Rodríguez-Escrich and
• Miquel A. Pericàs

Beilstein J. Org. Chem. 2009, 5, No. 56, doi:10.3762/bjoc.5.56

• Lewis base (O) and Lewis acid (B) character that could coordinate the reactant molecules (aldehyde and arylethylzinc) in an arrangement suitable for reaction. In this sense, it is noteworthy that when control experiments were done by using resin 2 under batch conditions with the Ph2Zn/Et2Zn combination