Quantum chemical calculations on S-centered 1,3-dipoles : 2. Reactivity of thiocarbonyl S-imides in perycyclic reactions

• Autorzy: Mlostoń, G. , Fabian, J.
• Języki publikacji: EN

Abstrakty

EN

Results of high level quantum chemical calculations on thiocarbonyl S-imides 1 are reported. The reactivity of thioformaldehyde S-imide (1a) (CH2S+NH-) in pericyclic reactions was calculated by density functional theory using gradient corrected functionals in conjunction with 6-31+G(d,p) and 6-31+G(3df, 3dp) basis sets. For the sake of comparison, conventional ab initio quantum chemical calculations at correlated levels of theory, such as MP2, QCISD(T) G1 and G2(MP2), were also performed. The predicted reactivity of the parent compound is compared with those of some closely related ylides (S-centered 1,3-dipoles), such as thioformaldehyde S-methylide (2a), thioformaldehyde S- oxide (3a) and thioformaldehyde S-sulfide (4a). To show the effect of substitution on structure and reactivity a series of acyclic and cyclic substituted thiocarbonyl S-imides 1b-k was calculated. The 1,3-electrocyclic ring closure of 1a to form thiaziridines 5 is predicted to be exothermic process by about 10 kcal/mol with activation energies of about 30 kcal/mol. The calculated reaction energies are considerably affected by higher angular momentum polarization functions, such as f-functions. In the case of some substituted thiocarbonyl S-imides, such as thiotropone S-imide (1i) and thiofluorenone S-imide (1j), the exothermicity of the ring closure reaction is lower than that of the parent compound. The concerted prototype [3+2]-cycloaddition of 1a with ethylene is strongly exothermic (about 50 kcal/mol) with the activation energy of about 20 kcal/mol. The energetics of both types of the pericyclic reactions of 1a appears closely related to that of 4a but differs more strongly from that of 3a. The contemporary knowledge on thiocarbonyl S-imides 1 is reviewed and discussed in conjunction with theoretical results.

Słowa kluczowe

EN

thiocarbonyl S-imides; thiaziridines; pericyclic reactions; valence isomerization; [3+2] cycloaddition; sulfur extrusion; ab-initio quantum chemistry; density functional theory

• Czasopismo: Polish Journal of Chemistry
• Rocznik: 1999
• Tom: vol. 73 nr 4
• Strony: 683-692

Twórcy

autor

Mlostoń, G.

autor

Fabian, J.

• Katedra Chemii Organicznej i Stosowanej Uniwersytet Łódzki ul. Narutowicza 68 90-136 Łódź,