Lithium Bromide/Water as Additives in Dearomatizing Samarium‐Ketyl (Hetero)Arene Cyclizations

New conditions for dearomatizing samarium‐ketyl (hetero)arene cyclizations are reported. In many examples of these samarium diiodide‐mediated reactions, lithium bromide and water can be used as additives instead of the carcinogenic and mutagenic hexamethylphosphoramide (HMPA). The best results were obtained for the cyclizations of N‐acylated indole derivatives delivering the expected indolines in good yields and excellent diastereoselectivities. A new type of cyclization delivering indolyl‐substituted allene derivatives is also described. The scope and limitations of the lithium bromide/water system are discussed.