Synthesis of New Pyrroline Nitroxides with Ethynyl Functional Group

Györgyi Úr,Tamás Kálai,Mária Balog,Balázs Bognár,Gergely Gulyás-Fekete,Kálmán Hideg

doi:10.1080/00397911.2015.1066391

Abstract

3-Substituted and 3,4-disubstituted pyrroline nitroxides containing an ethynyl group or two ethynyl groups were achieved by the reaction of a paramagnetic aldehydes with dimethyl (1-diazo-2-oxopropyl)phosphonate (Bestmann–Ohira reagent). The new compounds containing an ethynyl group were found to be useful building blocks in Sonogashira coupling, cyclization, and cycloaddition reactions producing potentially “azido-specific” cross-linking spin labels, paramagnetic ligands, and polyradical scaffolds.

Highlights

Nitroxides are stable free radical species with wide applications across a range of scientific disciplines including material science, biophysics, molecular biology, and medicine.[1]
To introduce the ethynyl group into pyrroline nitroxides, we tested the reaction of dimethyl (1-diazo-2-oxopropyl)phosphonate[14] with various paramagnetic aldehydes 1a–e [13,15,16,17] to furnish the corresponding acetylenes 2a–e under mild conditions, for example, stirring the 1.1 equiv
Referring to the band at 351 nm we have found K 1⁄4 13 dmÀ3=mol association constant, and saturation occurred at 2:1 ligand=metal ratio

Summary

Introduction

Nitroxides are stable free radical species with wide applications across a range of scientific disciplines including material science, biophysics, molecular biology, and medicine.[1] Nitroxides are often applied as initiators for the preparation of functional 30 and complex polymers,[2a] oxidants in organic chemistry in their oxoammonium form,[2b] spin labels in surveying structure of biomolecules,[3] building blocks for organic magnets,[4] and dynamic nuclear polarization agents in NMR spectroscopy,[5] just to mention but a few. The alkyne and terminal alkyne are functionally widely used in G. Reagents and conditions: (a) see Ref. 24; (b) see Ref. 13; (c) see Ref. 13; (d) BOR (1.1 equiv.), K2CO3(2.0 equiv.), MeOH, 3 h, 52%, this paper

Objectives

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Results

Conclusion