Structural Analysis of N,N-dimethyl-1,2-benzisothiazol-3-amine 1,1-dioxide by means of Matrix Isolation FTIR Spectroscopyand Quantum Chemical Calculations

R. ALMEIDA, A. GÓMEZ-ZAVAGLIA, A. KACZOR M.L. CRISTIANO AND R. FAUSTO

Algarve, Portugal

Congreso; XI European Symposium on Organic Reactivity; 2007

Universidade do Algarve

Saccharin (1,2-benzisothiazol-3(2H)-one-1,1-dioxide) is a commonly known substance as it is the oldest artificial sweetener. More recently, some of its derivatives have also been attracting an increased attention, as they show herbicidal, antimicrobial and antifungal activity and can also participate in enzymatic inhibition1. Because the benzisothiazole moiety is strongly electron-withdrawing, benzisithiazolyl ethers can be efficiently used as intermediates for selective reductive cleavage of C-O bonds, using catalytic trasnsfer methods2. In contrast, amino derivatives of benzisothiazole were inert to hydrogenolysis. Considering the synthetic relevance of methodologies for mild and selective C-N cleavage, for instance in bioorganic chemistry, it was decided to further investigate the structure of aminobenzisothiazoles. In this work, the amino-substituted derivative of saccharin, N,N-dimethyl-1,2-benzisothiazol-3-amine 1,1-dioxide (DiMeBAD) was isolated in solid argon and xenon and studied by matrix isolation FTIR spectroscopy and quantum chemical calculations. Since the computational description of saccharins is difficult because of the presence of the hypervalent S=O bonds in their structures, different computational methods (HF, B3LYP, MP2) implemented with basis sets of different sizes were applied to predict the geometry and vibrational frequencies of the studied compound. The experimentally obtained spectra could be successfully predicted at the B3LYP/6-311++G(3df,3pd) level of theory, stressing the adequacy of the B3LYP functional and of the Pople’s type 6-311 basis set, when duly augmented by extensive sets of polarization functions to study the considered family of compounds.