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Article

Microwave Assisted Facile Cleavage of 2,4-Dinitrophenylhydrazones to the Corresponding Carbonyl Compounds with N,N′-Dibromo-N,N′-1,2-ethanediylbis(p-toluenesulphonamide)

Department of Chemistry, Faculty of Science, Bu-Ali Sina University, PIN-65175, Hamadan, Iran
*
Author to whom correspondence should be addressed.
Molecules 2002, 7(5), 465-468; https://doi.org/10.3390/70500465
Submission received: 14 October 2001 / Accepted: 25 May 2002 / Published: 31 May 2002

Abstract

:
Deprotections of 2,4-dinitrophenylhydrazones to their corresponding carbonyl compounds have been carried out in good yields by using N,N-dibromo-N,N-1,2-ethanediylbis(p-toluene-sulphonamide (BNBTS, 2) under microwave irradiation.

Introduction

Carbonyl compound derivatives such as 2,4-dinitrophenylhydrazones and oximes are important intermediates in organic synthesis because of their use in the characterization and purification [1,2,3] of such compounds and the important role they play as protective groups for this functionality [4,5,6,7]. Consequently, the regeneration of carbonyl compounds from the corresponding 2,4-dinitrophenylhydrazones under mild conditions is an important process in synthetic organic chemistry. Several such procedures for regeneration of carbonyl compounds from 2,4-dinitrophenylhydrazones have been reported, for example: with Dowex-50 cation exchange resin [5], clayfen [6], potassium bromate [7], etc.
Although some are carried out under mild conditions most of these regenerations are often hazardous or use very toxic, expensive, or not readily available reagents, or reagents which need to be freshly prepared [8,9,10]. Thus, there is still a need to develop new and facile procedures for the regeneration of carbonyl compounds from 2,4-dinitrophenylhydrazones.

Result and Discussion

We have previously reported a convenient method for the deoximation of ketone and aldehyde oximes to their corresponding carbonyl compounds [11] using the new reagent BNBTS (2), prepared from N,N-1,2-ethanediylbis(p-toluenesulphonamide) (1) (Figure 1) [12]. Herein, we wish to report a mild and convenient method for the clean, fast and economical oxidative deprotection of 2,4-dinitrophenylhydrazones with this reagent under microwave irradiation.
Figure 1.
Figure 1.
Molecules 07 00465 g001
2,4-Dinitrophenylhydrazones 3 reacted with BNBTS (2) in CH2Cl2 under microwave irradiation to afford the corresponding carbonyl compounds 4 without any detectable byproducts (Scheme 1). The products of the reaction with BNBTS were isolated simply by filtering off compound 1 and evaporating the solvent from the filtrate. The results of the conversion of various 2,4-dinitrophenylhydrazones to their corresponding ketones and aldehydes are presented in Table 1.
Scheme 1.
Scheme 1.
Molecules 07 00465 g002
Table 1. Cleavage of 2,4-dinitrophenylhydrazones with BNBTS under microwave irradiation
Table 1. Cleavage of 2,4-dinitrophenylhydrazones with BNBTS under microwave irradiation
EntryR1R2ProductaReaction Times (min)Yield(%)
1CH3C6H5Acetophenone5091
2CH3p-ClC6H5p-Chloroacetophenone6092
3CH3p-MeOC6H5p-Methoxyacetophenone5094
4CH3p-BrC6H5p-Bromoacetophenone5093
5C6H5C6H5Benzophenone6090
6C6H5p-ClC6H5p-Chlorobenzophenone3092
7HC6H5Benzaldehyde5089
8Hp-ClC6H5p-Chlorobenzaldehyde4095
9Hp-MeC6H5p-Tolualdehyde5092
10Ho-MeOC6H5o-Methoxybenzaldehyde4092
11C6H5C6H5CH(OH)Benzoin5091
a Products were characterized by their physical constants, IR spectra and comparison with authentic samples.

Conclusions

From the results obtained, we find that the described procedure and the reaction conditions are simple. The reagent (BNBTS) is stable and the recovered reagent can be reused.

Experimental

General

IR spectra was recorded using a Shimadzu 435-U-04 spectrophotometer (KBr pellets). The 2,4-dinitrophenylhydrazones were prepared by a standard procedure [13]. The purity of compounds was checked by TLC (silica gel 60 F254/CHCl3 and CCl4/UV). A Shivaki Co. microwave (220 V, 700 W, RF output 2450 MHz) was used for the microwave irradiations.

General procedure for facile cleavage of 2,4-dinitrophenylhydrazones with BNBTS under microwave irradiation

A mixture of 2,4-dinitrophenylhydrazone (5 mmol), dichloromethane (15 mL) and BNBTS (5 mmol) was introduced in a flask and was refluxed under irradiated in a microwave oven at a power output of 700 W for the appropriate time as indicated in Table 1. After irradiation, cold water was added to hydrolyze the intermediate, and the insoluble sulfonamide 1 was removed by filtration and washed with cold dichloromethane (10 mL). The organic layer was separated from the aqueous layer, combined with the washes and dried with MgSO4. Dichloromethane was removed under reduced pressure gave the crude product. Solid products were recrystallized from diethyl ether, oily products were dissolved in ether and the ether solution washed, dried and concentrated.

Acknowledgements

The authors are grateful to Bu-Ali Sina University Research Council for partial financial support of this work.

References

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  8. Greene, T.W.; Wuts, P.G.M. Protective Groups in Organic Synthesis; John Wiley and Sons: New York, 1991. [Google Scholar]
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  10. Bandgar, B. P.; Shaikh, S. I.; Iyyer, S. Synth. Commun. 1996, 26, 1163.
  11. Khazaei, A.; Vaghei, R. G.; Tajbakhsh, M. Tetrahedron Lett. 2001, 42, 5099.
  12. Khazaei, A.; Shirdarreh, A. Synth. Commun. 1999, 29, 4079.
  13. Shriner, R. L.; Fuson, R. C.; Curtin, D. Y.; Morrill, T. C. The Systematic Identification of Organic Compounds, 6th Ed ed; John Wiley and Sons: New York, 1980. [Google Scholar]
  • Sample Availability: Samples of entries 1, 5, 7 and 11 are available from MDPI

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MDPI and ACS Style

Khazaei, A.; Vaghei, R.G. Microwave Assisted Facile Cleavage of 2,4-Dinitrophenylhydrazones to the Corresponding Carbonyl Compounds with N,N′-Dibromo-N,N′-1,2-ethanediylbis(p-toluenesulphonamide). Molecules 2002, 7, 465-468. https://doi.org/10.3390/70500465

AMA Style

Khazaei A, Vaghei RG. Microwave Assisted Facile Cleavage of 2,4-Dinitrophenylhydrazones to the Corresponding Carbonyl Compounds with N,N′-Dibromo-N,N′-1,2-ethanediylbis(p-toluenesulphonamide). Molecules. 2002; 7(5):465-468. https://doi.org/10.3390/70500465

Chicago/Turabian Style

Khazaei, Ardeshir, and Ramin Ghorbani Vaghei. 2002. "Microwave Assisted Facile Cleavage of 2,4-Dinitrophenylhydrazones to the Corresponding Carbonyl Compounds with N,N′-Dibromo-N,N′-1,2-ethanediylbis(p-toluenesulphonamide)" Molecules 7, no. 5: 465-468. https://doi.org/10.3390/70500465

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