Department of Chemistry, University of Calcutta, University College of Science, 92 A. P. C. Road, Kolkata-700009, India.
Sci Rep. 2013 Oct 18;3:2987. doi: 10.1038/srep02987.
We discover an important property of a small molecule ArCH(OMe)₂ which transforms catalytically inactive Pt(II)Br₂ procatalyst in situ to an powerful catalyst Pt(IV)-species for diverse annulation reaction. The powerful catalytic system enables selective activation of C₂-H/N-H and C₂-H/C₄-H of acetoacetanilide and C=O/C≡C of substituted butyne-1,2-dione for C-C/C-N, C-C/C-C and C-O/C-O bond-forming inter- and intramolecular annulation towards direct syntheses of functionalised 2-pyridones, cyclohexenones and 3(2H)-furanones respectively. In contrast to the common ligand, herein highly labile C-OMe bond of ArCH(OMe)₂ is expected to react with PtBr₂ towards generation of the high-valent active catalyst. Unlike catalyst promoter or initiator, the reaction does not occur with PtBr₂ in the absence of ArCH(OMe)₂. In situ generation of Pt(IV)-species and -OMe fragment of ArCH(OMe)₂ were confirmed from the UV-vis characteristic peaks about 260 nm and trapping of -OMe group respectively. These observations provide new prospects and perspectives in catalysis for innovative catalyst design.
我们发现了一种小分子 ArCH(OMe)₂ 的重要性质，它可以将催化惰性的 Pt(II)Br₂ 前催化剂原位转化为一种强大的催化剂 Pt(IV)-物种，用于多种环化反应。这个强大的催化体系能够选择性地活化乙酰乙酰苯胺的 C₂-H/N-H 和 C₂-H/C₄-H，以及取代丁炔-1,2-二酮的 C=O/C≡C，用于 C-C/C-N、C-C/C-C 和 C-O/C-O 键形成的分子内和分子间环化反应，分别直接合成功能化的 2-吡啶酮、环己烯酮和 3(2H)-呋喃酮。与常见配体不同，此处 ArCH(OMe)₂ 的高反应性 C-OMe 键预计会与 PtBr₂ 反应，生成高活性的催化剂。与催化剂促进剂或引发剂不同，在没有 ArCH(OMe)₂ 的情况下，PtBr₂ 不会发生反应。从大约 260nm 的 UV-vis 特征峰和 -OMe 基团的捕获分别证实了原位生成的 Pt(IV)-物种和 ArCH(OMe)₂ 的 -OMe 片段。这些观察结果为创新催化剂设计的催化提供了新的前景和视角。
