Solution structures of the mixed aggregates derived from lithium acetylides and a camphor-derived amino alkoxide.
Low-temperature (6)Li, (13)C, and (15)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)(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.
Briggs
T F
TF
Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301, USA.
Winemiller
M D
MD
Xiang
B
B
Collum
D B
DB
D002164:Camphor / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry*; D018020:Lithium Compounds / Q000737:chemistry*
D007659:Ketones; D018020:Lithium Compounds; D002164:Camphor