NMR elucidation of some ligands derived from the pentacycloundecane skeleton

Abstract

The complete NMR elucidation of three novel pentacycloundecane (PCU)-derived ligands is reported. 2D NMR techniques are used to overcome the problem of major overlapping of methine signals on the cage skeleton. The compounds were synthesized as potential ligands to be used in asymmetric catalysis. They represent the first instance where aromatic moieties have been attached directly to the cage skeleton using lithiation techniques. The X-ray crystal structure of one of the ligands was obtained. The X-ray structure was helpful in determining the potential NOESY interactions within the set of molecules. For the other ligands a high level Density Functional Theory (DFT) optimization was performed [B3LYP/6-31+g(d)] to visualize possible NOE interactions.

NMR elucidation of novel ligands derived from (R)-(+)-camphor

“…In order to assist with the visualization of the various through space interactions that could be expected for the molecules, density functional theory (DFT) optimizations using DFT (B3LYP) with the 6-31?g(d) basis set were employed for each of the ligands (1)(2)(3)(4). This approach has been carried out to good effect in our group for other NMR elucidation efforts [12][13][14].…”

“…Ligand 2 has recently been used to catalyze the asymmetric Diels-Alder reaction of 3-acryloyl-2-oxazolidinone with cyclopentadiene with moderate selectivity [15]. It has also been used to catalyze the alkylation of various aldehydes with diethylzinc with good selectivity [10].…”

Interplay of thermochemistry and Structural Chemistry, the journal (volume 19, 2008) and the discipline

“…In the next study Boyle et al [152] report the NMR study of three novel pentacycloundecane ligands. Difficulties associated with major overlapping of methine signals on the cage skeleton were solved by employing a 2D NMR technique.…”

NMR elucidation of novel SQ109 derivatives

“…NMR and computational study of 'cage' molecules such as pentacycloundecane and trishomocubane based compounds has been a major focus of our group for the past 5 years [25][26][27][28][29][30][31][32][33][34][35][36]. We recently reported the NMR elucidation of pentacycloundecane based tetraamines [37,38] which were screened for their anti-tuberculosis activities [39].…”