Hypervalent sulfur chemistry. Evidence for tetracoordinate sulfur(IV) and tricoordinate sulfur(II) intermediates in the reaction of p-tolyl sulfoxide with p-tolyllithium

Abstract

Ackerman, et al. mass spectrum m / e (re1 intensity, fragment) 234 (46, M+), 189 (4, (M+ -OEt), 161 (3, M+ -COzEt), 135 (100, C6H&NSt), 103 (32, C&CN+), 77 (16, CijH5*). Anal. Calcd for C11HloN202S: C, 56.40; H, 4.30. Found: C, 56.21; H, 4.45.Ethyl 3-(c~,a,ol-Trifluoro-m-~olyl)-1,2,4-thiadiazole-5-carboxylate (5b). Use of a similar procedure to that above (92.5-hr reaction time) gave product thiadiazole in 76% yield (isolated product) as a white solid, mp 7940.5" (from heptane), ir (CHCls) 5.72. 5.80 u.for C~~H~F~N Z O~S : C, 47.68; H, 3.00. Found: 6, 47.86; H, 2.84.Ethyl 3-(3,5-Dimethoxyphenyl)-1,2,4-thiadiazole-5-ca~~oxylate (5c). Use of a similar procedure to that above (92.5-hr reaction time) gave product thiadiazole in 94% yield (isolated) as a white solid, mp 125-126.5" (from dodecane), ir (CHC13) 5.72, 5.80 P . Anal. Calcd for C I~H I~N Z O~S : C, 53.05; H, 4.79. Found: C, 53.19; H, 4.90.3-Phenyl-1,2,4-thiadiazole (6). A mixture of 8 g (0.034 mol) of ethyl 3-phenyl-1,2,4-thiadiazole-5-carboxylate, 1.5 g (0.037 mol) of sodium hydroxide, 10 ml of ethanol, and 60 ml of water was heated with stirring on a steam bath for 1 hr. The resultant solution was allowed to cool and was acidified with 3.5 ml (0.042 mol) of concentrated hydrochloric acid. The resultant mixture, containing granular solid carboxylic acid, was heated on a steam bath until decarboxylation was complete. The mixture was cooled and extracted with ether. The ether layer was dried (MgS04) and concentrated under vacuum to give 5.5 g (99%) of colorless oil. Distillation of this material gave a single fraction, bp 76.5" (0.5 mm) [lit.9 bp 78-80" (0.3 mm)], nmr (CDC13) 6 9.90 (s, 1, 5..H), 8.37 (m, 2, ArH), 7.48 (m, 3, ArH). R = R' = Ph, 4115-15-5; 3, R = Ph, R' = p-ClCsH4, 50483-71-1; 3, R = p-CIC&, R' = Ph, 50483-72-2; 3, R = R' = p-ClCtjH4, 4115-17-7; 3, R = Ph, R' = p-MeCeH4; 50483-74-4; 3, R = p -MeC6H4, R' = Ph, 50483-75-5; 3, R = R' = p-MeCsHa, 17590-34-0; 3, R = Me, R' = Ph, 50483-77-7; 4, R = p-CIC6H4, R' = CHzCOzEt, 50483-78-8; 5a, 50483-79-9; 5b, 50483-80-2; 5c, 50483-81-3; 6,50483-82-4.