Regio- and Stereoselective 1,3-Dipolar Cycloaddition of Cyclic Azomethine Imines to Platinum(IV)-Bound Nitriles Giving 螖2-1,2,4-Triazoline Species

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• 作者：Andrey S. Smirnov ; Andreii S. Kritchenkov ; Nadezhda A. Bokach ; Maxim L. Kuznetsov ; Stanislav I. Selivanov ; Vladislav V. Gurzhiy ; Andreas Roodt ; Vadim Yu. Kukushkin
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：November 16, 2015
• 年：2015
• 卷：54
• 期：22
• 页码：11018-11030
• 全文大小：798K
• ISSN：1520-510X

文摘

The complex trans-[PtCl₄(EtCN)₂] (14) reacts smoothly at 25 掳C with the stable cyclic azomethine imines R¹CH鈺怤^aNC(O)CH(NHC(O)C₆H₄R³)C^bH(C₆H₄R²)^(a鈭?i>b) [R¹/R²/R³ = p-Me/H/H (8); p-Me/p-Me/H (9); p-Me/p-MeO/H (10); p-Me/p-Cl/p-Cl (11); p-MeO/p-Me/H (12); p-MeO/p-Cl/m-Me (13)], and the reaction proceeds as stereoselective 1,3-dipolar cycloaddition to one of the EtCN ligands accomplishing the monocycloadducts trans-[PtCl₄(EtCN){N^a鈺怌(Et)N^bC(O)CH(NHC(O)C₆H₄R³)CH(C₆H₄R²)N^cC^dHR¹}])^{(a鈥揹;b鈥揷)} [R¹/R²/R³ = p-Me/H/H (15); p-Me/p-Me/H (16); p-Me/p-MeO/H (17); p-Me/p-Cl/p-Cl (18); p-MeO/p-Me/H (19); p-MeO/p-Cl/m-Me (20)]. Inspection of the obtained and literature data indicate that the cycloaddition of the azomethine imines to the C鈮 bonds of HCN and of Pt^IV-bound EtCN has different regioselectivity leading to 螖²-1,2,3-triazolines and 螖²-1,2,4-triazolines, respectively. Platinum(II) species trans-[PtCl₂(EtCN){N^a鈺怌(Et)N^bC(O)CH(NHC(O)C₆H₄R³)CH(C₆H₄R²)N^cC^dHR¹}]^{(a鈥揹;b鈥揷)} [R¹/R²/R³ = p-Me/H/H (21); p-Me/p-Me/H (22); p-Me/p-MeO/H (23); p-Me/p-Cl/p-Cl (24); p-MeO/p-Me/H (25); p-MeO/p-Cl/m-Me (26)] were obtained by a one-pot procedure from 14 and 8鈥?b>13 followed by addition of the phosphorus ylide Ph₃P鈺怌HCO₂Me. 螖²-1,2,4-Triazolines N^a鈺怌(Et)N^bC(O)CH(NHC(O)C₆H₄R³)CH(C₆H₄R²)N^cC^dHR^{1(a鈥揹;b鈥揷)} [R¹/R²/R³ = p-Me/H/H (27); p-Me/p-Me/H (28); p-Me/p-MeO/H (29); p-Me/p-Cl/p-Cl (30); p-MeO/p-Me/H (31); p-MeO/p-Cl/m-Me (32)] were liberated from 21鈥?b>26 by the treatment with bis(diphenylphosphyno)ethane (dppe). Platinum(II) complexes 21鈥?b>26 were characterized by elemental analyses (C, H, N), high-resolution electrospray ionization mass spectrometry (ESI-MS), and IR and ¹H and ¹³C{¹H} NMR spectroscopies and single crystal X-ray diffraction in the solid state for 25路CH₃OH, 26路(CHCl₃)_0.84. The structure of 26 was also determined by COSY-90 and NOESY NMR methods in solution. Quantitative evaluation of several pairs of interproton distances obtained by NMR and X-ray diffraction agrees well with each other and with those obtained by the MM+ calculation method. Platinum(IV) complexes 15鈥?b>20 were characterized by ¹H NMR spectroscopy. Metal-free 6,7-dihydropyrazolo[1,2-a][1,2,4]triazoles (27鈥?b>32) were characterized by high-resolution ESI-MS and IR and ¹H and ¹³C{¹H} NMR spectroscopies and single crystal X-ray diffraction for 29路CDCl₃. Theoretical density functional theory calculations were carried out for the investigation of the reaction mechanism, interpretation of the reactivity of Pt-bound and free nitriles toward azomethine imines and analysis of the regio- and stereoselectivity origin.