Less than 3 % loss of (£)-l and (Z)-l as measured against the internal standards was observed. Most data points fell between 20 and 80% conversion of (Z)-l to (£)-l. The pseudo-first-order rate constants were calculated by a least-squares computer program, and errors are reported with two standard deviations. Table I reports these results.
The stereochemical course of nucleophilic reactions with cyclopropane derivatives, (+)-methyl 1-(S)cyano-2-(f?)-phenylcyclopropanecarboxylate ((+)-(£)-!), and (+)-methyl l-(E)-cyano-2-(E)-phenylcyclopropanecarboxylate ((+)-(Z)-l), have been studied. The four stereomers were prepared in an optically pure state: (+)-(£)-1 gave mp 53-54°, [ ]25546 + 251°( c 0.54, EtOAc); (-)-(£)-! gave mp 53-54°, [a]25546 -25 (c 0.62, EtOAc);(+)-(Z)-l gavemp 90.5-91.5°, [a]2S546 +175°(c0.15, EtOAc); (-)-(Z)-1 gavemp 91-91.5°, [ ]25646 -175°( c0.145, EtOAc). The relative configurations of the E and Z isomers were established by nmr spectral comparisons, and by K = 20 for (Z)-l (£)-l at 25°( see below). The absolute configurations of the Z diastereomers were assigned by converting (+)-(Z)-l to (+)-methyl 2-(S)-phenyl-l-(S)-cyclopropanecarboxylate, whose absolute configuration was known. The relative configurations of esters (+)-(£)-! and (-)-(Z)-l were established by converting their respective acids to enantiomeric dicyano compounds with a single chiral center. Thus (+)-(£)-! gave (+)-l ,1-di-
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