Thermal Reactions of Regioisomeric 1,2,4‐Trithiolane S‐Oxides

Abstract

The products of the gas‐phase pyrolysis of two regioisomeric 1,2,4‐trithiolane S‐oxides were collected in an argon matrix at 10 K and studied by means of spectroscopic as well as computational methods. Whereas the main products of the pyrolysis of the “symmetrical” S‐oxide were identified asthioformaldehyde S‐oxide and thioformaldehyde S‐sulfide, the “non‐symmetrical” S‐oxide gave predominantly dithioformic acid, which exists as a mixture of s‐cis and s‐trans conformers. We present a rationalization of the reaction pathways including density functional theory computations.

Photochemical Formation and Reactivities of Substituted Oxathiiranes in Low‐Temperature Argon Matrices

“…In analogyto the thermolysisof 1,2,4-trithiolane 4-oxide described earlier, [13] substrate 9 was evaporated and subjected to high-vacuum flash thermolysis at 600°C (Scheme 3).…”

Thermolysis of 3,3,5,5‐Tetramethyl‐1,2,4‐trithiolane 1‐Oxide: First Matrix Isolation of the HOSS· Radical

“…These results can also be explained by invoking a [3+2] cycloreversion of the starting material 2a . In this case, 9a can be recognized as a dipolarophile, and 4a is the corresponding 1,3‐dipole 2c. The same reaction pathway was observed for 3,3,5,5‐tetramethyl‐1,2,4‐trithiolane 4‐oxide ( 2b ).…”

“…Spectroscopic analysis of the matrix‐isolated products led to the identification of thioformaldehyde S ‐oxide (sulfine) ( 9a ) formed together with dithioformic acid ( 7 ) (Scheme ). The reaction mechanism was elucidated by DFT computations at the B3LYP/6‐311+G(3df,3pd) level of theory (see Experimental Section for details), and – in this case – the initial step is an allowed 1,4‐H shift leading to open‐chain intermediate 11 , which spontaneously splits into a mixture of final products 7 and 9a (Scheme ) 2c. Structure 3a can also be considered as a cyclic thiosulfinate, and the initial step of the observed fragmentation corresponds to the typical reactivity of S ‐alkyl alkanethiosulfinates under pyrolytic conditions 3…”

Honorary Membership of the Gesellschaft Deutscher Chemiker: G. S. Fischer and E. Winterfeldt / Liebig Lectureship: G. Mloston / Innovation Prize in Medicinal/Pharmaceutical Chemistry: C. Ottmann / Raimund Stadler Prize: A. Walther / DuPont Young Professor Grants: X. Duan and J. Seibel / Members of the Deutsche Akademie der Technikwissenschaften: E. W. Meijer and P. Schwille / Körber Prize: M. Mann

“…Mloston’s research interests are in heterocyclic systems, sulfur compounds, fluorine‐containing organic compounds, reactive intermediates, and asymmetric catalysis. He has reported in Angewandte Chemie on a carbon–sulfur triple bond,3a and in the European Journal of Organic Chemistry on 1,2,4‐trithiolane‐ S ‐oxides 3b…”