Preparation of Functionalized Diaryl- and Diheteroaryllanthanum Reagents by Fast Halogen-Lanthanum Exchange

摘要

Aryl and heteroaryl halides (X=Br, I) undergo a fast and convenient halogen-lanthanum exchange with nBu2LaMe, which leads to functionalized diaryl- and diheteroaryllanthanum derivatives. Subsequent trapping reactions with selected electrophiles, such as ketones, aldehydes, or amides, proceeded smoothly at -50°C in THF, affording polyfunctionalized alcohols and carbonyl derivatives. Kinetic competition experiments revealed a similar reactivity trend as for Br/ Mg exchange, but 10~6-times higher rates, making it comparable to Br/Li exchange.