Chiral tris[/3-diketonato]europium(III) chelates 1-14 have been synthesized and tested for their effectiveness in inducing chemical shifts ( ) between corresponding resonances of enantiomeric organic substances.Judged by the dual criteria of generality of application as reagents for determining enantiomeric composition and ease of preparation, the most useful of these chiral shift reagents are tris[d,i/-dicampholylmethanato]europium(III)(1, Eu(dcm)3), tris[3-trifluoroacetyl-i/-nopinonato]europium(III) (9), and tris[3-trifluoroacetyW-camphorato]europium(III) (10). Compound 1, Eu(dcm)3, is the most effective reagent for the resolution of enantiotopic resonances; reagents 9 and 10 are considerably less effective, but are more easily prepared. It is not presently possible to predict in any detail the influence of a particular chiral shift reagent on a mixture of enantiomers, and achieving useful resolution between the signals of enantiotopic protons in complex, polyfunctional structures may require testing several chiral shift reagents, and varying sample concentrations and temperature. Chiral shift reagents are applicable in principle to the determination of enantiomeric composition of most "hard" organic bases; they are not effective with most "soft" bases, with acids, or with certain chelating agents. Conditions for use of these

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Gases in the Reaction of Phenylmagnesium Bromide with Halides 493 copper were found to be ineffective as catalysts anethole hydrobromide and Grignard reagents, in the synthesis of hexestrol dimethyl ether from Chicago, Illinois

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