Chasing an Elusive Alkoxide: Attempts to Synthesize [OC(tBu)(CF3)2]?

The synthesis of the alkoxide [OC(tBu)(CF3)2]? by the reaction of tBuM-reagents (M = Li; MgX) with hexafluoroacetone was attempted. This alkoxide was anticipated to be a good building block for novel weakly coordinating anions. However, in all attempted syntheses – also supported by theoretical DFT calculations – it was shown that [H]? addition is favored over [tBu]? addition. Thus compounds like [(Li(OC(H)(CF3)2]4·2Et2O (1) and (CF3)2(H)COMgCl·(OEt2)2 (4) were formed. An unexpected result was the formation of (THF)3LiO(CF3)2OC(H)(CF3)2(2), an addition compound built from [(CF3)2C(H)O]? and hexafluoroacetone. The alkoxy-alkoxide 2 could be useful for further applications.