18301-46-7Relevant articles and documents
Characterization of covalent Ene adduct intermediates in "hydride equivalent" transfers in a dihydropyridine model for NADH reduction reactions
Libby, R. Daniel,Mehl, Ryan A.
experimental part, p. 57 - 66 (2012/03/26)
A study of the reactions of an NADH model, 1,4-di(trimethylsilyl)-1,4- dihydropyridine, 7, with a series of α,β-unsaturated cyano and carbonyl compounds has produced the first direct evidence for an obligatory covalent adduct between a dihydropyridine and substrate in a reduction reaction. The reactions were monitored by NMR spectroscopy. In all reactions studied, the covalent adduct was the first new species detected and its decomposition to form products could be observed. Concentrations of adducts were sufficiently high at steady-state that their structures could be determined directly from NMR spectra of the reaction mixtures; adduct structures are those expected from an Ene reaction between 7 and the substrate. This first reaction step results in transfer of the C4 hydrogen nucleus of 7 to the substrate and formation of a covalent bond between C2 of the dihydropyridine ring and the substrate α-atom. Discovery of these Ene-adduct intermediates completes the spectrum of mechanisms observed in NADH model reactions to span those with free radical intermediates, no detectable intermediates and now covalent intermediates. The geometry of the transition state for formation of the Ene adduct is compared with those of theoretical transition state models and crystal structures of enzyme-substrate/inhibitor complexes to suggest a relative orientation for the dihydropyridine ring and the substrate in an initial cyclic transition state that is flexible enough to accommodate all observed mechanistic outcomes.
A novel type of nucleophilic substitution reactions on nonactivated aromatic compounds and benzene itself with trimethylsiliconide anions.
Postigo,Rossi
, p. 1197 - 1200 (2007/10/03)
[reaction: see text]. The reaction of fluorobenzene with Me3Si- anion (1) in HMPA at room temperature surprisingly affords o- and p-fluorotrimethylsilylbenzenes (substitution of aromatic H for TMS, 76% yield) 7a and 7b and also 14% of trimethylsilylbenzene (2). Benzene itself reacts at 50 degrees C to furnish 4 in 45% yield. Pyridine affords p-trimethylsilylpyridine quantitatively. Mechanistic studies are presented.
Reactions of 1,4-Bis(trimethylsilyl)-1,4-dihydropyridines with Carbonyl Compounds: A New Method for Regioselective Synthesis of 3-Alkylpyridines
Tsuge, Otohiko,Kanemasa, Shuji,Naritomi, Toshio,Tanaka, Junji
, p. 1497 - 1504 (2007/10/02)
A new method for the alkyl group introduction at the 3-position of pyridines is described: Reductive disilylation of pyridine, its 2-methyl, 3-methyl, and 4-methyl derivatives affords the corresponding 1,4-disilyl-1,4-dihydropyridines.Tn the presence of a catalytic amount of tetrabutylammonium fluoride, these dihydropyridines smoothly react with a variety of aldehydes and ketones to give 3-alkylpyridines.
