Synthesis of Heteroaryl Imines: Theoretical and Experimental Approach to the Determination of the Configuration of C=N Double Bond

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• 作者：Mario Amati ; Carlo Bonini ; Maurizio D'Auria ; Maria Funicello ; Francesco Lelj ; Rocco Racioppi
• 刊名：Journal of Organic Chemistry
• 出版年：2006
• 出版时间：September 15, 2006
• 年：2006
• 卷：71
• 期：19
• 页码：7165 - 7179
• 全文大小：650K
• 年卷期：v.71,no.19(September 15, 2006)
• ISSN：1520-6904

文摘

The reaction between an iminophosphorane with furan-2-carbaldehyde, thiophene-2-carbaldehyde, furan-3-carbaldehyde, and thiophene-3-carbaldehyde at 60 C gives the corresponding trans imines in 53-84% yields, while the same reaction at 100 C gives a mixture of the corresponding trans and cis imines.Whether the iminophosphorane reacted with 5-nitrofuran-2-carbaldehyde or 5-nitrothiophene-2-carbaldehyde only the trans imines were obtained in 85-89% yields. The irradiation of the imines obtainedfrom thiophene-2-carbaldehyde and thiophene-3-carbaldehyde gave the corresponding photocyclizationproducts. Cis/trans stereochemistry of the imines can be assigned simulating the UV-vis spectra. In thecase of the imine from furan-2-carbaldehyde the computed spectra are characterized by an intenseabsorption at 361 and 357 nm respectively for the trans-1 and trans-2 structures. No other absorptionsof comparable intensity have been predicted: the agreement with the experimental spectrum can beconsidered good. Furthermore, the experimental weak peaks at 280 and 270 nm can be associated to thecomputed transitions at 278 and 260 nm for the trans-1 isomer. Several minima of the energy surfacecan be assigned to the cis isomer, and they all present a very similar energy. The structures of the cis-1and cis-2 isomers present quite coincident computed electronic spectra. In both cases, the computedspectrum shows two principal features. For the cis-1 structure, the first characteristic absorption is locatedat 414 nm and the second one at 284 nm. For the cis-2 structure, the first feature is located at 412 nmand the second one at 286 nm. The second transition is computed somewhat more intense. The experimentalspectrum could be the consequence of similar populations of the planar cis structure (cis-3) and nonplanarcis structures (cis-1, cis-2, and their enantiomers).