Chemistry on Benzopentathiepin. Reactions of Benzopentathiepin with Active Methylene Compounds in the Presence of Base

Abstract

z o p e n t a t h i e p i n (BPTI reacted with various active methylene compounds such as malononitrile, ethyl cyanoacetate, ethyl acetoacetate, acetylacetone, ethyl 2-chloroacetoacetate, and ethyl a-chloroproplonate in the presence of base such as triethylamine or sodium ethoxide to give dithlins, dithioles, or 1.2.4-trithiin in satisfactory yields.The success of a facile synthesis of BPT,' which is a typical cyclic polysulfide and shows a certaln fungicidal effectr2 stimulated some organosulfur chemists to %"" % l yield in the presence of NaOEt in EtOH-THF.Acetylacetone gave similarly 2acetyl-l,3-benzoditniole (3b) (Scheme 3).since the dithiole tz was found to ?i% react with NaOEt to afford 3a7, 3a and 3b seem to be formed by the nucleophilic " " l ""* ""% attack of ethoxide on acetyl carbonyl group in followed by protonation.In these reactions, BPT was shown apparently to serve as a 1.4-dication synthon B. "" 2.3: oil; 'H nmr ( c D c ~~) S 1.30 (t, J 7.0 HZ, 3 ~, -c H ~c H ~) , 2.41 ( s , 3 ~, -m 3 ) , % l 4.32 (q, J 7.0 Hz, -CE2CH3), and 6.96-7.30(m, 4H.arom); ir (neat) 1730 and 1710 cm-'; ms (70 eVl m/z 268 ( M + ) .Anal.Calcd for Cl2Kl2O3S2: C, 53.71; H, 4.51.Found: C, 53.91; H, 4.55.3a: Colorless crystals; mp 41 .0'C (from ""% hexane); 'H nmr (CDC13) 6 1.25 (t, J 7.0 Hz, 3H, -CH2CH3), 4.20 (q, J 7.0 HZ, 2H.CH2CH3), 5.23 ( S , lH, -CH<), and 6.95-7.26(m, 4H.arom); ir (KBr) 1753 cm-' ; ms (70 eV) m/z 226 (M+).Anal.Calcd for ClOH1 002S2: C, 53.07; H, 4.45.Found: C, 53.12; H, 4.45.1,3-Dithioles 2.3 and 3a were also obtained upon treating ethyl 2-chloroaceto-""% %% acetate with BPT in the presence of base as shown in Scheme 4. These results suggest that BPT functions as a l,4-dipole synthon A.