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Transformations of β-aryl-N-Cbz-α,β-didehydro-α-amino esters with hydrazine hydrate

Transformations of β-aryl-N-Cbz-α,β-didehydro-α-amino esters with hydrazine hydrate AbstractCyclizations of Cbz-protected α,β-didehydro-β-arylalanine esters 1 with excess hydrazine hydrate afforded mixtures of the expected 3-pyrazolidinones 2 and the unexpected 1-amino-5-benzylidenehydantoins 6 and N-Cbz-β-arylalanine hydrazides 7. Presumably, the pyrazolidinones 2 and hydantoins 6 are formed as primary products via competitive 1,2- and 1,4-addition of hydrazine hydrate followed by cyclization, whereas β-arylalanine hydrazides 7 are formed as secondary products via reductive cleavage of the C(5)–N(1) bond in pyrazolidinones 2. The overall selectivity depends on the reaction time and on the β-substituent in the starting dehydroalanine ester 1. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Zeitschrift für Naturforschung B de Gruyter

Transformations of β-aryl-N-Cbz-α,β-didehydro-α-amino esters with hydrazine hydrate

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Publisher
de Gruyter
Copyright
©2016 by De Gruyter
ISSN
0932-0776
eISSN
1865-7117
DOI
10.1515/znb-2015-0221
Publisher site
See Article on Publisher Site

Abstract

AbstractCyclizations of Cbz-protected α,β-didehydro-β-arylalanine esters 1 with excess hydrazine hydrate afforded mixtures of the expected 3-pyrazolidinones 2 and the unexpected 1-amino-5-benzylidenehydantoins 6 and N-Cbz-β-arylalanine hydrazides 7. Presumably, the pyrazolidinones 2 and hydantoins 6 are formed as primary products via competitive 1,2- and 1,4-addition of hydrazine hydrate followed by cyclization, whereas β-arylalanine hydrazides 7 are formed as secondary products via reductive cleavage of the C(5)–N(1) bond in pyrazolidinones 2. The overall selectivity depends on the reaction time and on the β-substituent in the starting dehydroalanine ester 1.

Journal

Zeitschrift für Naturforschung Bde Gruyter

Published: Jun 1, 2016

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