Solution Structures of the Mixed Aggregates Derived from Lithium Acetylides and a Camphor-Derived Amino Alkoxide
2001-08-23T00:00:00Z (GMT) by
Low-temperature <sup>6</sup>Li, <sup>13</sup>C, and <sup>15</sup>N 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)<sub>3</sub>(R*OLi) mixed tetramer and a <i>C</i><sub>2</sub>-symmetric (RCCLi)<sub>2</sub>(R*OLi)<sub>2</sub> mixed tetramer depending on the stoichiometries. The corresponding (RCCLi)(R*OLi)<sub>3</sub> 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.