Reaktionen von Halogenthiazylen: Darstellung, Strukturen und Eigenschaften von perhalogenierten 1,2‐Thiazinen [1]

Reactions of Halogeno Thiazyls: Preparation, Structures, and Properties of Perhalogenated 1,2‐Thiazines Reactions of (XSN) n ( n = 1,3; X = F, Cl) with perfluorobutadiene provide the 1λ 4 ,2‐thiazines 1a and 1b . The structure of 1 b was determined by single‐crystal X‐ray diffraction analysis. From the molecular structure it is evident that a formal [4 + 2] cycloaddition has occured. Fluorination with KF converts 1 b almost quantitatively into 1 a . The 1λ 4 ,2‐thiazine 1 a does not exhibit fluorinating properties towards chloroalkanes but undergoes reaction with CH 3 OH and Me 3 SiNMe 2 to form 1 c and 1 d , respectively. 1,2‐Thiazine oxide 3 is obtained from 1 a or 1 b and (Me 3 Si) 2 O. Treatment of 1 b with AgAsF 6 in SO 2 yields perfluoro‐1,2‐thiazin‐1‐ium hexafluoroarsenate ( 4 ) as the main product. No reaction is observed between FSN and hexa‐chlorobutadiene. The 1,2‐thiazines 5, 6 , and 9 are prepared from tetrachlorothiophene dioxide ( 7 ) and FSN. Fluorine abstraction reactions of 5 and 6 with formation of the expected 1,2‐thiazin‐1‐ium ions 11 and 13 , respectively, provide evidence for the structures of 5 and 6 . These cations are very sensitive to hydrolysis and are converted into the corresponding ketones 12 and 14 . The very unstable intermediate CF 3 SSN, formed on treating Me 3 SiSCF 3 or B(SCF 3 ) 3 with FSN, decomposes to CF 3 S x CF 3 ( X = 2–4), S 4 N 4 , S 8 , and N 2 . No addition product can be detected when CF 3 SSN prepared in situ is treated with dienes.