Sarish Sankaranarayana Pillai, Samuel Prinson P, Roesky Herbert W, Schulzke Carola, Nijesh Karikkeeriyil, De Susmita, Parameswaran Pattiyil
Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen (Germany).
Ernst-Moritz-Arndt-Universität, Institut für Biochemie, Arbeitskreis Bioanorganische Chemie, Felix-Hausdorff-Strasse 4, 17487 Greifswald (Germany).
Chemistry. 2015 Dec 21;21(52):19041-7. doi: 10.1002/chem.201503137. Epub 2015 Nov 23.
A β-diketiminate Al compound (1) with an exocyclic double bond reacts with two equivalents each of benzophenone and 2-benzoylpyridine in a [4+2] cycloaddition to generate bicyclic and tricyclic compounds 2 and 3, respectively. Compound 2 consists of six- and eight-membered aluminium rings, whereas 3 has two five- and one eight-membered ring. Compounds 2 and 3 were characterized by a number of analytical tools including single-crystal X-ray diffraction. The quantum mechanical calculations suggest that the dissociation of the solvent molecule from 1 would lead to an active species 1A having two 1,4-dipolar 4π electron moieties, in which the electrophilic site is the Al atom and the nucleophilic positions are polarized exocyclic and endocyclic C=C π bonds. The detailed mechanistic study shows that the dipolarophiles, benzophenone, and 2-benzoylpyridine undergo double cycloaddition with two 1,4-dipolar 4π electron moieties of 1A. Herein, the addition of one molecule of the dipolarophile promotes the addition of the second one.
一种带有环外双键的β-二酮亚胺铝化合物（1）与两当量的二苯甲酮和2-苯甲酰基吡啶分别发生[4+2]环加成反应，生成双环化合物2和三环化合物3。化合物2由六元环和八元铝环组成，而化合物3有两个五元环和一个八元环。化合物2和3通过多种分析手段进行了表征，包括单晶X射线衍射。量子力学计算表明，溶剂分子从1解离会产生具有两个1,4-偶极4π电子部分的活性物种1A，其中亲电位点是铝原子，亲核位置是极化的环外和环内C=Cπ键。详细的机理研究表明，亲偶极体二苯甲酮和2-苯甲酰基吡啶与1A的两个1,4-偶极4π电子部分发生双环加成反应。在此，一分子亲偶极体的加成促进了第二分子亲偶极体的加成。
