Mixed Aggregates of the Dilithiated Koga Tetraamine: NMR Spectroscopic and Computational Studies. (20th July 2016)

• Record Type: Journal Article
• Authors: Ma, Yun; Mack, Kyle A.; Liang, Jun; Keresztes, Ivan; Collum, David B.; Zakarian, Armen
• Is Part Of: Angewandte Chemie. Volume 128:Number 34(2016)
• Page Start: 10247
• Page End: 10251
• Publication Date: 2016-07-20
• Subjects: Aggregation -- Enantioselektivität -- Lithium -- NMR-Spektroskopie -- Synthesemethoden; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201605199
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: 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.