- Electron and Hydrogen Transfer Reductions of Some 2,4-Disubstituted Pyridines
-
New synthesis of 2,4-diacetylpyridine 1 was undertaken by Claisen condensation of 2,4-diethoxycarbonylpyridine 2a with ethyl acetate, followed by hydrolysis of the intermediate 3. Reduction of 1 with zinc or its salt in hydrochloric, formic or acetic acids afforded mixtures of the ketocarbinol 4 dicarbinol 5 or diethyl 6 pyridine derivatives. Formation of 6 as the complete reduction product was chemically proved to proceed via 4 and 5. Electrochemical reduction of 2a leads to 2,4-dimethylpyridine 7, and that of 1 gave rise to a mixture of 5 and 6 along with 2,4-diethyl-1,2,5,6-tetrahydropyridine 8 and 2,4-diethylpiperidine 9. Finally, metal hydride reduction of 1 gave 5, and that of diesters 2 or diacid chloride 10 derivatives afforded 2,4-dihydroxymethylpyridine 11.
- Attia, A.,El-Salam, O. I. Abd,Youssef, T. E.
-
p. 351 - 362
(2007/10/03)
-
- Helical and Planar-chiral Pyridinophanes - A New Synthesis and Structure/Chiroptic Relationships
-
A new two-step synthesis for the strained helical oxaphanes 1-5 and for a systematic series of novel structural isomeric (2,4)-pyridinophanes (6-10) is presented.The energy barriers for ring inversion of some intermediate phanes and the kinetics of racemization of the phanes are determined.Separation and enrichment of enantiomers is achieved by HPLC on cellulose tris(3,5-dimethylphenyl)carbamate and poly(triphenylmethyl-methacrylate), resp.The circular dichroism curves of the isomers are compared with those of the corresponding protonated pyridinium compounds.The influence of the chromophor orientation on the circular dichroism is discussed. - Keywords: Circular dichroism/ Helical molecules/ Metacyclophanes/ Oxametacyclophane/ Pyridinophanes
- Przybilla, Klaus Juergen,Voegtle, Fritz
-
p. 347 - 356
(2007/10/02)
-