Department of Chemistry, Southern Federal University, Zorge str. 7, 344090 Rostov-on-Don, Russian Federation.
Department of Chemistry and Pharmacy, North Caucasus Federal University, Pushkin str. 1a, 355017 Stavropol, Russian Federation.
Org Biomol Chem. 2023 Apr 26;21(16):3388-3401. doi: 10.1039/d3ob00286a.
4-Bromo- and 4,5-dibromo-1,8-bis(dimethylamino)naphthalenes were arylated with arylboronic acids under Suzuki reaction conditions to provide 4-aryl- and 4,5-diaryl-1,8-bis(dimethylamino)naphthalenes, respectively. The interaction of 4,5-dibromo-1,8-bis(dimethylamino)naphthalene with pyridin-3-ylboronic acid was accompanied by heterocyclization leading unexpectedly to the formation of ,,,-tetramethylacenaphtho[1,2-]pyridine-3,4-diamine. Dynamic H NMR experiments showed fast interconversion between and conformers of 4,5-diaryl-1,8-bis(dimethylamino)naphthalenes in CDCl solution at room temperature. The free energy of the rotational isomerization was determined to be ∼14.0 kcal mol for 4,5-di(-tolyl) and 4,5-di(naphthalen-2-yl) derivatives. X-ray analysis of 4,5-diaryl-1,8-bis(dimethylamino)naphthalenes revealed a high degree of structural deformation due to internal steric repulsions between both -dimethylamino and -aryl groups. In crystals, 4,5-di(naphthalen-1-yl)-1,8-bis(dimethylamino)naphthalene molecules exist exclusively in the most stable form, while for 4,5-di(naphthalen-2-yl) and 4,5-di(-tolyl) counterparts, only the -form is realized. The introduction of two -aryl substituents in the 1,8-bis(dimethylamino)naphthalene scaffold affected the basic properties, making the 4,5-diphenyl derivative 0.7 p units less basic. The protonation of 4,5-diaryl-1,8-bis(dimethylamino)naphthalenes leads to dramatic changes in their structures. Compared to the corresponding bases, the inter-nitrogen distance in these salts noticeably decreases whereas -aromatic rings move away from each other demonstrating the so-called "clothespin effect". This lowers the barriers of /-isomerization; as a result, protonated molecules with -tolyl and even -(naphthalen-2-yl) substituents exist in crystals as mixtures of rotamers.
4-溴-和 4,5-二溴-1,8-双（二甲氨基）萘分别与芳基硼酸在铃木反应条件下芳基化，分别得到 4-芳基-和 4,5-二芳基-1,8-双（二甲氨基）萘。4,5-二溴-1,8-双（二甲氨基）萘与 3-吡啶硼酸的相互作用伴随着杂环化，出乎意料地导致,,,-四甲基吖啶并[1,2-]吡啶-3,4-二胺的形成。动态 NMR 实验表明，在室温下，CDCl3 溶液中 4,5-二取代-1,8-双（二甲氨基）萘的两种构象（ 和 ）快速互变。确定 4,5-二（-甲苯基）和 4,5-二（萘-2-基）衍生物的旋转异构化自由能约为 14.0 kcal/mol。X 射线分析表明，由于两个 -二甲氨基和 -芳基基团之间的内部空间排斥，4,5-二取代-1,8-双（二甲氨基）萘的结构发生了高度变形。在晶体中，4,5-二（萘-1-基）-1,8-双（二甲氨基）萘分子仅以最稳定的 形式存在，而对于 4,5-二（萘-2-基）和 4,5-二（-甲苯基）对应物，仅实现了 -形式。在 1,8-双（二甲氨基）萘支架中引入两个 -芳基取代基会影响其基本性质，使 4,5-二苯基衍生物的碱性降低 0.7 p 单位。4,5-二取代-1,8-双（二甲氨基）萘的质子化导致其结构发生显著变化。与相应的碱相比，这些盐中氮原子之间的距离明显减小，而 -芳环彼此远离，表现出所谓的“衣夹效应”。这降低了 /-异构体化的势垒；因此，带有 -甲苯基甚至 -（萘-2-基）取代基的质子化分子在晶体中以旋转异构体混合物的形式存在。
