Toward N,P-Doped π‑Extended PAHs: A One-Pot Synthesis to Diannulated 1,4,2-Diazaphospholium Triflate Salts

A novel method for the one-pot synthesis of diannulated 1,4,2-diazaphospholium triflate salts by a Me3SiOTf-mediated self-condensation of dichlorophosphaneyl aza-(poly)­cyclic aromatic hydrocarbons (aza-(P)­AHs; namely, pyridine, quinoline, phenanthridine, and benzo­[d]­thiazole) is reported. The diannulated 1,4,2-diazaphospholium triflate salts are characterized by multinuclear NMR spectroscopy, X-ray analysis, as well as their calculated NICS values, underlining their aromatic character. Quantum mechanical calculations shed light on the intermolecular reaction mechanism. Follow up chemistry, such as the halogenation reaction with XeF2 or SO2Cl2 with the dipyridinium derivative selectively yields the respective dihalo-σ4,λ5- and tetrahalo-σ5,λ6-diazaphospholium triflate salts. The dihalo-σ4,λ5-diazaphospholium triflate salt serves well as a surrogate for the introduction of the cationic 2-(1,2′-bipyridin)-1-iumyl ligand (1,2′-bipyl), the monocationic structural isomer of the prototypical 2,2′-bipyridine ligand (2,2′-bipy).

本文报道了一种通过三氟甲磺酸三甲基硅酯（Me3SiOTf）介导的二氯膦基氮杂（多）环芳烃（aza-(P)AHs，即吡啶、喹啉、菲啶与苯并[d]噻唑）的一锅法自缩合反应，用以合成双稠合1,4,2-二氮杂磷鎓三氟甲磺酸盐（diannulated 1,4,2-diazaphospholium triflate salts）。该类化合物通过多核核磁共振波谱、X射线晶体衍射分析以及计算得到的核独立化学位移（Nucleus-Independent Chemical Shifts, NICS）值进行表征，证实了其芳香性特征。量子力学计算阐明了该分子间反应的反应机理。后续衍生化反应中，二吡啶鎓衍生物与二氟化氙（XeF2）或磺酰氯（SO2Cl2）发生卤代反应，可选择性得到对应的二卤代-σ⁴,λ⁵-与四卤代-σ⁵,λ⁶-二氮杂磷鎓三氟甲磺酸盐。二卤代-σ⁴,λ⁵-二氮杂磷鎓三氟甲磺酸盐可作为引入阳离子型2-(1,2′-联吡啶)-1-鎓基配体（1,2′-bipyl）的替代试剂，该配体是经典2,2′-联吡啶（2,2′-bipy）配体的一价阳离子结构异构体。