Children learn through play, and they learn more than adults might expect. Science experiments are a great way to spark their curiosity, get their minds active, and encourage them to do something that doesn¡¯t involve a screen. 3030-47-5, C9H23N3. A document type is Article, introducing its new discovery. 3030-47-5
Stereochemistry of solvation of benzylic lithium compounds: Structure and dynamic behavior
Several sec-benzylic lithium compounds, both externally coordinated, [alpha-(trimethylsilyl)benzyl]-lithium¡¤PMDTA (12) and p-tert-butyl-alpha-(dimethylethylsilyl)benzyllithium¡¤TMEDA (13), and internally coordinated, [alpha-[[[cis-2,5-bis(methoxymethyl)-1-pyrrolidinyl]methyl]dimethylsilyl]-p- tert-butylbenzyl]lithium (14) and [alpha-[[[(S)-2-(methoxymethyl)-1-pyrrolidinyl]methyl]dimethylsilyl]benzyl] lithium (15), have been prepared. Ring 13C NMR shifts indicate that 12-15 have partially delocalized structures. Externally solvated allylic lithium compounds are found to be delocalized, and only some internally coordinated species are partially delocalized. Compound 15 exists as > 95% of one stereoisomer of the two invertomers at Calpha. This is in accord with a published ee of > 98% in products of the reactions of 15 with aldehydes. All four compounds show evidence of one-bond 13C-6Li spin coupling, ca. 3 Hz, which indicates a small detectable C-Li covalence. Averaging of the 13C-6Li coupling of 12 with increasing temperature provides the dynamics of intermolecular C-Li bond exchange, with DeltaH?ex = 9 ¡À 0.5 kcal mol-1. Carbon-13 NMR line shape changes due to geminal methyls, and ligand carbons gave similar rates of inversion at Calpha in 13 (externally solvated) and 14 (internally solvated), DeltaH?inv ? 4.9 ¡À 0.5 kcal mol-1. By contrast, barriers to rotation around the ring-Calpha bonds vary widely, depending on the mode of lithium coordination, DeltaH?rot ? 8 ¡À 0.5 to 19 ¡À 1.0 kcal mol-1. Some mechanisms for these processes are proposed.
Interested yet? Keep reading other articles of 20439-47-8!, 3030-47-5
Reference£º
Metal catalyst and ligand design,
Ligand Template Strategies for Catalyst Encapsulation – NCBI