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W . Verboom et al. J Convenient methods for the preparation of di(1-alkynyl) sulfides, sulfoxides and sulfones 6-Phenyl-ZH-pyran-2,4(3 H J -dione (8)A solution of 3-acetyl-6-phenyl-2H-pyran-2,4(3H)-dione (6, 2 g) in 90% sulfuric acid (10 ml) was heated in an oil bath (bath temp. 1700) to 135-148 for one minute. The solution was cooled and poured on ice. The separated pyrandione (8) was recrystallized from ethanol, 1.1 g (6873, m.p. 246248" (decomp.)15. The analytical sample was recrystallized from ethanol, colourless prisms with the same m.p. Mixed m.p. with 6-phenyl-2H-pyran-2,4(3H)-dione obtained from dehydrobenzoylacetic acid (4b) showed no depression. C,,H,O, (188.18) calcd. C 70.21, H 4.29; found C 70.09, H 4.60. -Phenylhexane-l ,S,S-trioneA solution of 2-methyl-6-phenyl-4-pyrone (0.95 g, 5 mmol) in methanol (40 ml) and 45 % aqueous potassium hydroxide (10 ml) was heated on a water bath for 20 minutes, cooled, diluted with water (200 ml), acidified with concentrated hydrochloric acid to pH 4, and extracted with ether (3 x 10 ml). After removal of the solvent, the residue was crystallized from methanol and the pale yellow needles (0.48 g, 49 %) of I-phenylhexane-1,3,5-trione, m.p.102-103°, were obtained. The compound'6 described earlier had the m.p. 10&107° (brown needles). C I Z H I 2 O 3 (204.22) calcd.C 70.58, H 5.92; found C 70.69, H 5.80. Oxidation of an equimolar mixture of octane-2,4.5,7-tetrone (la) and I ,6-diphenylhexane-l,3,4,6-tetrone (lb) with lead tetraacetateAbstract. Di( I-alkynyl) sulfides and the corresponding sulfoxides are obtained in high yields from lithium alkynides and sulfur dichloride or thionyl chloride, respectively. The di( I-alkynyl) sulfoxides and also the corresponding sulfones (prepared by oxidation of di( I-alkynyl) sulfides with m-chloroperbenzoic acid) react very rapidly with disodium sulfide, selenide or telluride to form six-membered heterocyclic compounds.

Abstract. The reaction of 1,Cdithiin (1) with n-butyllithium has been examined. At -1 loo in tetrahydrofuran 2-lithio-1 ,Cdithiin (2) is sufficiently stable to allow of the preparation of derivatives. Anion (2) undergoes ring opening by a 1 ,Zelimination at -600; subsequent methylation and hydrolytic work-up gives Z-HCd-S-CH=CH-SMe (6), or Z-MeC-C-S-CH=CH-SMe (7). At about -So butyllithium attacks sulfur in the intermediary Z-LiC-C-S-CH=CH-SLi (4), leading to Z-Bus-CH=CH-SLi (8), and LiC-CLi. These results are not in agreement with the mechanism proposed by Parham et al. for benzo-1,4-dithiin and 2,5-diphenyl-1 ,Cdithiin. We studied also the reactivity of 2,6-dimethyl-l,Cdithiin (13), and 2,6-di-tert-butyl-1,4-dithiin (25), towards butyllithium. Starting from 13 the otherwise, difficultly accessible tri-and tetramethyl-I ,Cdithiins could be prepared in high yield. The ring opening provides a valuable method for the synthesis of stereochemically pure Z-1 -(alkynylthio)-2-(alkylthio)alkenes and Z-l-(butylthio)-2-(alkylthio)alkenes.

Abstract. Reaction of 1-(chloromethylthio)-I-alkynes (RC=C-S-CH,Cl, R = alkyl or phenyl) with an alkali metal sulfide, selenide or telluride gives 4-substituted 1,3-dithioles together with the corresponding 1,3-thiaselenoles and 1,3-thiatelluroles in good yields. The compounds RC-C-S--CH,CI can be obtained either from lithium alkynethiolates (RCEC-SLi) and BrCH,CI or from alkynyllithium (RC=C-Li) and chloromethyl thiocyanates (CICH,S-C=N).

Die aus Alkylbromiden (I) zugänglichen Dithioallylester (II) ergeben nach Metallierung Enthiolate (III), die bei 50°C in einer Claisen‐Umlagerung Dithiosäuren (IV) bilden.