Stabilizing N-tosyl-2-lithioindoles with bis(N,N′-dimethylaminoethyl) ether—a non-cryogenic procedure for lithiation of N-tosylindoles and subsequent addition to ketones

A practical procedure suitable for large scale lithiation of N-tosylindoles and subsequent addition to ketones is described. Bis(N,N′-dimethylaminoethyl) ether was found to stabilize 2-lithio-N-tosylindole 1A at −25 °C [The temperatures cited are internal temperatures unless otherwise stated]. Addition of this reagent allows the lithiation of N-tosyl indoles and subsequent addition to ketones to operate at −25 °C, a temperature suitable for large scale reactions.