作者:Christian Roussel、Alexandru T. Balaban、Ulf Berg、Michel Chanon、Roger Gallo、Gerd Klatte、Joseph A. Memiaghe、Jacques Metzger、Daniela Oniciu、Johanna Pierrot-Sanders
DOI:10.1016/s0040-4020(01)88642-7
日期:1983.1
The effect of the shape of a methylgroup on reactivity, which cannot be accounted for by considering a methylgroup as a spherical substituent with the appropriate van der Waals radius, was considered in kinetics of alkylalion of substituted pyridines and barriers to rotation and ground state conformations of an isopropyl group attached to a planar framework. The perturbation of a methylgroup by an
Base catalysed rearrangements involving ylide intermediates. Part 7. The rearrangements of allyl(pentadienyl)- and propynyl(pentadienyl)ammonium cations. The [5,4] sigmatropic rearrangement
作者:Trevor Laird、W. David Ollis、Ian O. Sutherland
DOI:10.1039/p19800002033
日期:——
The basecatalysedrearrangements of the cations (7), (17), (22), and (27) gave the enamines (9), (18), (23), and (28), which on hydrolysis yielded the aldehydes (10), (19), (24), and (29) respectively. The reactions are shown to be concerted [5,4] sigmatropic rearrangements proceeding via a nine-membered transition state involving 10π electrons. The basecatalysedrearrangements of the 3-phenylprop-2-ynyl
2′′-terpyridine and biq = 2,2′-bisquinoline). The photocatalytic system is not only highly efficient but also tolerant to amino acid residues. The combination of this photocatalyst with glutamate dehydrogenase enabled the controllable and efficient synthesis of L-glutamate to be realized. A mechanism involving light-induced ligand exchange, decarboxylation and hydride transfer has been proposed. Kinetic
Excellent correlation between substituent constants and pyridinium N-methyl chemical shifts
作者:Sha Huang、Jesse C.S. Wong、Adam K.C. Leung、Yee Man Chan、Lili Wong、Myrien R. Fernendez、Amanda K. Miller、Weiming Wu
DOI:10.1016/j.tetlet.2009.06.081
日期:2009.9
Substituents on the pyridinium ring of N-methylpyridinium derivatives, especially those on the 2- or 4-position, have a large effect on the 1H and 13C NMR chemical shifts of the N-methyl group. Reasonable correlations between the chemical shift changes and the resonance substituentconstants are observed. The dual substituent parameter approach provides an excellent correlation when a combination of