Richter Ferdinand, Birchall Nicholas, Feil Christoph M, Nieger Martin, Gudat Dietrich
Institut für Anorganische Chemie, University of Stuttgart, 70550 Stuttgart, Germany.
Department of Chemistry, University of Helsinki, FIN-00014 Helsinki, Finland.
Molecules. 2022 Jul 25;27(15):4747. doi: 10.3390/molecules27154747.
The successful use of 1,3,4,2-triazaphospholenes (TAPs) as organo-catalysts stresses the need for efficient synthetic routes to these molecules. In this study, we establish the [1 + 4]-cycloaddition of PBr to azo-pyridines as a new approach to preparing pyrido-annellated TAPs in a single step from easily available precursors. The modular assembly of the azo-component via condensation of primary amines and nitroso compounds along with the feasibility of post-functionalization at the P-Br bond under conservation of the heterocyclic structure allows, in principle, to address a wide range of target molecules, which is illustrated by prototypical examples. The successful synthesis of a transition metal complex confirms for the first time the ability of a TAP to act as a P-donor ligand. Crystallographic studies suggest that hyperconjugation effects and intermolecular interactions induce a qualitatively similar ionic polarization of the P-Br bonds in TAPs as in better known isoelectronic diazaphospholenes.
1,3,4,2-三氮杂磷杂茂（TAPs）作为有机催化剂的成功应用凸显了开发这些分子高效合成路线的必要性。在本研究中，我们确立了PBr与偶氮吡啶的[1 + 4]环加成反应，这是一种从易于获得的前体一步制备吡啶并环化TAPs的新方法。通过伯胺与亚硝基化合物的缩合对联氮组分进行模块化组装，以及在保留杂环结构的情况下对P-Br键进行后官能化的可行性，原则上能够合成多种目标分子，典型示例对此进行了说明。过渡金属配合物的成功合成首次证实了TAP作为P供体配体的能力。晶体学研究表明，超共轭效应和分子间相互作用在TAPs中诱导出与更为人熟知的等电子二氮杂磷杂茂中定性相似的P-Br键离子极化。
