Wednesday, April 25, 2007

Can J Chem: Volume 85, Number 3, March 2007 (157-239)

Zirconium(IV) chloride-catalyzed synthesis of 1,5-benzodiazepine derivatives
K. Srinivasa Reddy, Ch. Venkateshwar Reddy, M. Mahesh, K. Rosi Reddy, P.V.K. Raju, and V.V. Narayana Reddy Can. J. Chem./Rev. can. chim. 85(3): 184-188 (2007)

Abstract: Zirconium tetrachloride efficiently catalyzes the cyclocondensation reaction of o-phenylenediamine and a ketone in refluxing 1,2-dichloroethane to afford the corresponding 2,3-dihydro-1H-1,5-benzodiazepine in high yield. The formation of specific regioisomers and their structural elucidation are reported for the first time.

Key words: zirconium tetrachloride, o-phenylenediamines, ketones, 1,5-benzodiazepines, 1H NMR, regioisomers.

Triazene derivatives of (1,x)-diazacycloalkanes. Part VIII. Synthesis and characterization of a series of 1,4-di[2-aryl-1-diazenyl]-2-methylpiperazines1
Naomi Hunter, Reid Tingley, Brad Peori, and Keith Vaughan Can. J. Chem./Rev. can. chim. 85(3): 189-196 (2007) Full text

Abstract: A series of 1,4-di-[2-aryl-1-diazenyl]-2-methylpiperazines (4a–n) have been synthesized by the reaction of 2-methylpiperazine with 2 equiv. of the appropriate diazonium salt. The products have been characterized by IR and NMR spectroscopy, and the molecular composition has been verified by HR-EIMS, with accurate mass measurement of the molecular ion. The presence of a chiral centre at C2 of the piperazine ring in the bistriazene 4 creates a multitude of diastereotopic protons in the methylene groups of the piperazine ring, as evidenced by the complexity of the NMR spectra, which nevertheless can be fully assigned in some cases, such as the tolyl- (4h) and phenyl- (4j) derivatives. These two compounds also show a discrimination between the two N-arydiazenyl groups, as evidenced by the doubling of several aromatic-carbon signals in the 13C NMR spectra. The assignment of the proton and carbon signals in 4h and 4j has been aided by the use of 2D NMR spectroscopy. A DEPT spectrum of 4j clearly discriminates the methylene carbons and also indicates the methine carbons of the piperazine ring. COSY spectra provide clear information about the interactions between diastereotopic protons; when these results are combined with the results of HSQC spectroscopy, the proton and carbon signals can be fully correlated, leading to an unequivocal assignment of the proton and carbon atoms of the piperazine ring. The HSQC spectrum of 4j also gives a complete correlation of the aromatic-proton and -carbon signals. These results compare favorably with the previously reported assignments of proton and carbon signals for triazenes of type 1 and bistriazenes of type 3.

Key words: triazene, bistriazene, piperazine, 2-methylpiperazine, diastereotopic protons, diazonium coupling, 2D NMR, COSY, DEPT, HSQC.

1D and 2D NMR investigations of the micelle-formation process in 8-phenyloctanoate micelles
Josette M. Landry, D. Gerrard Marangoni, Michael D. Lumsden, and Robert Berno Can. J. Chem./Rev. can. chim. 85(3): 202-207 (2007)

Abstract: The micellization process of sodium 8-phenyloctanoate in a deuterated aqueous solution was studied, using 1H NMR spectroscopy and two-dimensional (2D) nuclear Overhauser enhancement spectroscopy (NOESY). 1H NMR spectra, acquired for the sodium 8-phenyloctanoate before and after the critical micelle concentration (CMC) value, showed that large chemical-shift changes were observed for both the aromatic proton peaks and the peaks for the methylene protons near the terminal phenyl group. The plots for the methylene protons near the headgroup do not show these large chemical-shift changes. These observations support the view that the terminal phenyl ring of the surfactant is primarily located in the micellar interior. The 2D NOESY experiments show significant cross-peaks, between the phenyl protons and the methylene protons of the surfactant, that substantiate the conclusions on those drawn from NMR aromatic solute induced shift (ASIS) experiments on the same and similar systems. All these observations are consistent with the Gruen model of the micelle and previous NMR NOESY experiments for other surfactant systems.

Key words: surfactants, micelles, NMR, NOESY.

No comments: