Free energies of 2-amino-1,5-diazaspiro[4.5]dec-1-en-5-ium chlorides monohydrates and arylsulfonates formation at β-aminopropioamidoximes arylsulfochlorination

Abstract

We have previously obtained new spiropyrazolinium compounds by arylsulfochlorination of β-aminopropioamidoximes. But it was found that under certain conditions, the main or by-product of β-(thiomorpholine-1-yl)propioamidoxime tosylation was 2-amino-8-thia-1,5-diazaspiro[4.5]dec-1-en-5-ium chloride monohydrate. In the case of other β-aminopropioamidoximes, only 2-amino-1,5-diazaspiro[4.5]dec-1-en-5-ium arylsulfonates were isolated. The aim of the work is to perform a theoretical comparison of reactions of tosylation, para- and ortho-nitrobenzenesulfochlorination of β-aminopropioamidoximes and evaluate the propability of 2-amino-1,5-diazaspiro[4.5]dec-1-en-5-ium chlorides monohydrates formation. Methodology. The calculations were performed using Gaussian 09 package by DFT/B3LYP/6-31G++(d,p) method. Results and discussion. Thermodynamically preferred products were identified by comparing the Gibbs free energies of reactions. Chemical stability and reactivity parameters for 2-amino-8-thia-1,5-diazaspiro[4.5]dec-1-en-5-ium chloride monohydrate, tosylate, para-nitrophenylsulphonate and ortho-nitrophenylsulphonate were predicted based on calculated HOMO and LUMO energies. In most cases arylsulfonates are thermodynamically favorable, except when the initial substrate is β-(thiomorpholine-1-yl)propioamidoxime. Conclusion. 2-Amino-8-thia-1,5-diazaspiro[4.5]dec-1-en-5-ium chloride monohydrate is more preferred compared to the corresponding arylsulphonates.