Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853-1301, USA.
Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA.
Angew Chem Int Ed Engl. 2016 Aug 16;55(34):10093-7. doi: 10.1002/anie.201605199. Epub 2016 Jul 20.
A combination of (1) H, (6) Li, (13) C, and (15) N NMR spectroscopies and density functional theory computations explores the formation of mixed aggregates by a dilithium salt of a C2 -symmetric chiral tetraamine (Koga's base). Lithium halides, acetylides, alkoxides, and monoalkylamides form isostructural trilithiated mixed aggregates with few exceptions. (6) Li-(13) C and (6) Li-(15) N couplings reveal heretofore undetected transannular contacts (laddering) with lithium acetylides and lithium monoalkylamides. Marked temperature-dependent (15) N chemical shifts seem to be associated with this laddering. Computational studies shed light on the general structures of the aggregates, their penchant for laddering, and the stereochemical consequences of aggregation.
（1）H、（6）Li、（13）C 和（15）N 核磁共振波谱和密度泛函理论计算相结合，研究了 C2 对称手性四胺（Koga 碱）的二锂盐形成混合聚集体的过程。除了少数例外，锂卤化物、炔化物、烷氧基化物和单烷基亚胺形成同构的三锂混合聚集体。（6）Li-（13）C 和（6）Li-（15）N 偶合揭示了以前未检测到的与锂炔化物和锂单烷基亚胺的跨环接触（梯形化）。显著的温度依赖的（15）N 化学位移似乎与梯形化有关。计算研究揭示了聚集体的一般结构、它们的梯形化倾向以及聚集的立体化学后果。
