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).

本文报道了一种基于三甲基硅基三氟甲磺酸酯（Me₃SiOTf）介导的二氯膦基氮杂（多）环芳烃（aza-(P)AHs，即吡啶、喹啉、菲啶及苯并[d]噻唑）的自缩合反应，用于一锅法合成双稠合1,4,2-二氮杂磷鎓三氟甲磺酸盐的新方法。通过多核核磁共振波谱法、X射线分析以及计算得到的核独立化学位移（Nucleus-Independent Chemical Shift, NICS）值对所合成的双稠合1,4,2-二氮杂磷鎓三氟甲磺酸盐进行了表征，证实了其芳香性特征。量子力学计算揭示了该分子间反应的反应机理。后续衍生化实验表明，以二吡啶衍生物与二氟化氙（XeF₂）或硫酰氯（SO₂Cl₂）进行卤化反应时，可选择性生成相应的二卤代-σ⁴,λ⁵-及四卤代-σ⁵,λ⁶-二氮杂磷鎓三氟甲磺酸盐。其中，二卤代-σ⁴,λ⁵-二氮杂磷鎓三氟甲磺酸盐可作为阳离子型2-(1,2′-联吡啶)-1-鎓基配体（1,2′-bipyl）的替代底物，该配体是经典2,2′-联吡啶配体（2,2′-bipy）的单阳离子结构异构体。