Solution structure and chelation properties of 2-thienyllithium reagents.

[reaction: see text] The solution and chelation properties of 2-thienyllithium reagents with potential amine and ether chelating groups in the 3-position and related model systems have been investigated using low temperature 6Li, 7Li, 13C, and 31P NMR spectroscopy, 15N-labeling, and the effect of solvent additives. In THF-ether mixtures at low temperature 3-(N,N-dimethylaminomethyl)-2-thienyllithium (4) is ca. 99% dimer (which is chelated) and 1% monomer (unchelated), whereas 3-(methoxymethyl)-2-thienyllithium (5) is <10% dimer.