Replacement of HMPA in Samarium Diiodide Promoted Cyclizations and Reactions of Organolithium Compounds
Tripyrrolidinophosphoric acid triamide (TPPA) can replace carcinogenic HMPA as a Lewis basic additive in many reactions involving samarium ketyls. In most cases, yields and selectivities of cyclizations of (het)aryl, alkenyl, and alkynyl ketones are similar. TPPA is also a good substitute of HMPA in the O-silylation of an ester enolate and in reactions oflithiated 1,3-dithiane. All these results clearly demonstrate that in many cases the use of HMPA can be avoided.