42520-09-2Relevant academic research and scientific papers
DISSYMMETRY OF CERTAIN SUBSTITUTED DIPYRIDOTETRAAZAPENTALENES
Pereira, David E.,Clauson, Gary L.,Leonard, Nelson J.
, p. 4931 - 4946 (1987)
In a two-step synthesis from staring amines, a series of compounds has been prepared in which steric crowding (1b,c,d,f) was introduced into the "bay region" of pyridoimidazoimidazopyridine (1a).This forces the tetracyclic ring system into non-planarity.Two hexa-heterohelicenes 2a and b were prepared that incorporate the 1,3,4,6-tetraazapentalene ring system and provide molecular crowding in the "bay region" due to the terminal rings, which similarly distort the hexacyclic ring system from planarity.Single crystal X-ray structure determinations revealed that the compounds (1b,c,d,f,2a and b) exist as enantiomeric pairs in the crystalline state.
Obtention of 2,2-(diethoxy) vinyl lithium and 2-methyl-4-ethoxy butadienyl lithium by Arene-catalysed lithiation of the corresponding chloro derivatives. Synthetic applications
Si-Fodil, Mohamed,Ferreira, Humberto,Gralak, Jean,Duhamel, Lucette
, p. 8975 - 8978 (2007/10/03)
Vinylic lithium reagents 1 and 2 could be obtained by the title procedure from their chloro precursors 5 and 6 instead of the less stable corresponding bromo derivatives 3 and 4. Condensation with carbonyl compounds leads to interesting synthetic applications such as a two steps synthesis of retinal 13 from β-cyclocitral 10.
12-hetero substituted 6,11-ethano-6,11-dihydrobenzo (b) quinolizinium salts and compositions and method of use thereof
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, (2008/06/13)
1-Hetero substituted 6,11-ethano-6,11-dihydrobenzo[b]quinolizinium salts, pharmaceutical compositions containing them, and methods for the treatment or prevention of neurodegenerative disorders or neurotoxic injuries utilizing them.
Nucleoside Annelating Reagents: N-(tert-Butyloxycarbonyl)-2-bromoacetamide and 2-Chloroketene Diethyl Acetal
Leonard, Nelson J.,Cruickshank, Kenneth A.
, p. 2480 - 2488 (2007/10/02)
The title reagents undergo cyclocondesation reaction with the amidine-like moiety of tri-O-acetyladenosine and cytidine (and related compounds) to form a new five-membered ring (etheno bridging), substituted with a (tert-butoxycarbonyl)amino or an ethoxy function.Some of the products exhibit useful fluorescence properties.Removal of the tert-butoxycarbonyl group with standard conditions gives the corresponding, somewhat unstable amino compounds which can be conveniently characterized as the corresponding N-acetyl derivatives.The reagents introducing additional substitution on the etheno bridge, with enhanced fluorescence, also suggest the possibility of cross-linking functionalization.
13C NMR study of the structures of some acyclic and cyclic ketene acetals
Taskinen,Pentikaeinen
, p. 2365 - 2370 (2007/10/04)
A 13C NMR study of the spatial structures of some acyclic and cyclic ketene acetals (for example, ketene dimethyl acetal and 2-methylene-1,3-dioxolane) has been carried out. The conclusions obtained are based on observation of the effect of structural changes on the 13C NMR chemical shift of the β carbon on the ketene moity. Since the extent of p-π conjugation and hence the 13C chemical shift of this carbon depend on the spatial orientation of the alkoxy groups about the O-C(sp2) bonds, the shift concerned may be used as a measure of the planarity of the system. The most stable retamers of ketene dimethyl acetal are s-cis,s-cis (planar) and s-cis,gauche (slightly nonplanar), in the order of decreasing stability. For ketene dialkyl acetals, the relative stability of the planar s-cis,s-cis form decreases with increasing bulkiness of the alkyl groups, but at least for primary and secondary alkyl groups, the s-cis,s-cis rotamer appears to be the most favored species. The conformations of 5- to 8-membered cyclic ketene acetals are discussed and compared with those of the corresponding cyclic vinyl ethers and hydrocarbons.
