Solution structures of the mixed aggregates derived from lithium acetylides and a camphor-derived amino alkoxide

Low-temperature Li-6, C-13, and N-15 NMR spectroscopies reveal that mixtures of lithium cyclopropylacetylide or lithium phenylacetylide (RCCLi) and a vicinal amino alkoxide derived from camphor (R*OLi) in THF/pentane afford an asymmetric (RCCLi)(3)(R*OLi) mixed tetramer and a C-2-symmetric (RCCLi)(2)(R*OLi)(2) mixed tetramer depending on the stoichiometries. The corresponding (RCCLi)(R*OLi)(3) mixed tetramer is not observed. R*OLi-mediated additions of PhCCLi to benzaldehyde proceed with up to an 8:1 enantiomeric ratio that depend on both the choice of R*OLi and the PhCCLi/R*OLi stoichiometries. The results are considered in light of a previously proposed mechanism for the 1,2-addition to a trifluoromethyl ketone.