- Synthesis, crystal structure, and different local conformations of pyridine-imide oligomers
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In this article, we report a new approach toward synthesis of pyridine-imide oligomers (PIOs). Using this approach, both dimer and trimer were one-pot synthesized from acylation of monomeric monoamide with monomeric dichloride. The yield of trimer was dependent on the alkoxyl terminals: it was 30% for methoyl group, whereas it was 95% for 3-chloro-1-propoxyl terminal. Acylation of dimeric monoamide with monomeric dichloride produced trimer, tetramer, and pentamer in a yield of 34%, 33%, and 28%, respectively. The synthesis was proposed to be mediated through an exchange between pyridine-2-carboxamide and pyridine-2-carbonyl chloride, both forming intramolecular or intermolecular hydrogen-bonds between pyridine-nitrogen and pyridine-2-amide hydrogen atoms. Crystal structure from three trimers with different terminal groups was reported. Analysis on the crystal structures revealed that these three trimers had different local conformations. The different local conformations were originated from the structural tunability of the imide unit in either the coplanarity or bond parameters.
- Zhu, Hengheng,He, Weiwei,Zhan, Chuanlang,Li, Xiao,Guan, Zisheng,Guo, Fengqi,Yao, Jiannian
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experimental part
p. 8458 - 8464
(2011/11/13)
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- Iminium Salts from α-Amino Acid Decarbonylation. Application to the Synthesis of Octahydroindoloquinolizines
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Iminium salts, formed regiospecifically by the decarbonylation of tertiary α-amino acids, have been applied to the synthesis of substituted tetrahydro-β-carbolines.In this manner the octahydroindoloquinolizines 5-8 were prepared.Several useful methods for the synthesis of the requisite tertiary pipecolic acids 1-4 were developed.These include alkylation of secondary α-amino esters with tryptophyl bromide and alkylation of tryptophan methyl ester with α,ω-dibromo esters.Following deprotection, the resulting tertiary α-amino acids were heated in phenylphosphonic dichloride to give the cyclized products in good yield.The presence of other substituents α or β to the basic nitrogen induces stereoselectivity in the ring closure.When this substituent is an α-carboxylic acid, it can be replaced by hydrogen through decarbonaylation followed by reduction of the resulting iminium salt.
- Johansen, Jon E.,Christie, Bradley D.,Rapoport, Henry
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p. 4914 - 4920
(2007/10/02)
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- POLYORGANOMETALLIC HETEROCYCLES. 2,6-DILITHIOPYRIDINE
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Metal-halogen exchange between 2,6-diiodo- and 2,6-dibromopyridine and two equivalents of n-butyllithium gives 2,6-dilithiopyridine.On quenching with either carbon dioxide followed by esterification, methanol or dimethyl disulfide the dilithio compound gives a methyl 2,6-pyridinedicarboxylate, pyridine, or 2,6-dithiomethylpyridine, respectively.A convenient procedure for halogen-halogen exchange is also described.
- Newkome, George R.,Roper, Jerry M.
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p. 147 - 153
(2007/10/02)
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