A Mild Method for the Formation of Tosylhydrazone Derivatives from Keto Esters

References

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• The ratio of stereoisomers was measured by 1H NMR on the bases of higher downfield shift of N-H for the hydrogen bonded Z isomer /7, 7–9, 4 ppm for the E isomers and 11, 9–12, 2 ppm for the Z isomers/. No attempts were made to separate the stereoisomers of hydrazones
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• Although a straightforward explanation of stereo-selectivity still awaits more detailed studies, inspection of the molecular models suggest, that the preferential formation of the Z isomer of 5d may due to the strong hydrogen bond existing in the molecule, and the predominance of the E isomer of 5c may be the result of the steric hindrance in the corresponding Z isomer
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