Sulfides alkynyl

Thioketenes can be prepared in several ways, from carboxyHc acid chlorides by thionation with phosphoms pentasulfide [1314-80-3] 2 5 ketene dithioacetals by -elimination, from l,2,3-thiadia2oles with flash pyrolysis, and from alkynyl sulfides (thioacetylenes). The dimeri2ation of thioketenes to 2,4-bis(alkyHdene)-l,3-dithietane compounds occurs quickly. They can be cleaved back pyrolyticaHy (63). For a review see Reference 18. 

The Lewis acid catalyst 53 is now referred to as the Narasaka catalyst. This catalyst can be generated in situ from the reaction of dichlorodiisopropoxy-titanium and a diol chiral ligand derived from tartaric acid. This compound can also catalyze [2+2] cycloaddition reactions with high enantioselectivity. For example, as depicted in Scheme 5-20, in the reaction of alkenes bearing al-kylthio groups (ketene dithioacetals, alkenyl sulfides, and alkynyl sulfides) with electron-deficient olefins, the corresponding cyclobutane or methylenecyclobu-tene derivatives can be obtained in high enantiomeric excess.18... 

An jco-OT o-cyclisation of a,o -diynes promoted by bis(pyridyl)iodonium(i) tetrafluoroborate (IPy2BF4) has been described for the first time and is an excellent route for accessing a variety of sulfur-containing heterocycles when employing alkynyl sulfides (Scheme 49) <1998AGE3136>. 

Di(l-alkynyl)sulfides are formed in excellent yields, if (freshly distilled) sulfur dichloride is added to a solution or suspension of a lithium alkynylide in Et20 [106). In an analogous manner, di(l-alkynyl)sulfoxides are formed from thionyl chloride and an alkynyllithium [106], while sulfinyl chlorides R S(=0)G may be used to prepare the sulfoxides RC=CS(=0)R Preliminary experiments suggest that interaction between alkynyllithium and sulfonyl chlorides R S02C1 can give both sulfones ROCSOjR and chlofo-alkynes RCsCCl [2). 

Preparation of Di(l-alkynyl(sulfides and Di(l-alkynyI)suifoxides from Alkynyllithium and Sulfur Dichloride or Thionvl Chloride... 

Addition of sodium sulfide to alkynyl sulfides, S(C = CR)2, also yields 2,6-disubstituted 1,4-dithiins (75RTC163). 

A general method of synthesis of l-hetera-4-telluracyclohexa-2,5-dienes 90 is founded in the nucleophilic addition of telluride anion to type 91 diacetylene derivatives. The telluride dianion is prepared in situ from the elements in liquid ammonia. The reaction was carried out with methanol or mixtures with DMSO and liquid ammonia as solvents, with the following diacetylenes di(l-alkynyl)sulfides (73RTC1326), I-alkynylethynyl sulfides (75RTCI63), di(l-alkynyl)sulfones (78RTC244), and di(l-alkynyl)phosphi-noxides (75RTC92). 

The reaction with 2-mercaptobenzoxazole gives 1-alkynyl sulfides (Scheme 68). 

A detailed study of the halocyclisation of unsaturated benzyl sulfides has shown that tetrahydrothiopyran formation is favoured from alkenyl sulfides through 6-endo-trig and 6-exo-trig modes. However, for alkynyl sulfides only the 6-exo-dig cyclisation is predominant, leading to dihydrothiopyrans (95JOC6468). 

The halocyclization of unsaturated benzyl sulfides is influenced by the degree of unsaturation. Thus alkenyl sulfides yield tetrahydrothiopyrans through (y-endo-trig and (y-exo-trig modes (Equation 141), whereas alkynyl sulfides afford 2-methylenetetrahydrothiopyrans by a 6-exo-dig cyclization (Equation 142) <1995JOC6468>. 

With a sulfone capable of giving 5-exo-dig vs. 6-endo-dig, or 6-exo-dig vs. 1-endo-dig cyclisations, mixtures are obtained, with exo cyclisation dominating. With alkynyl sulfides, solely exo products are obtained. 

The additions of disodium telluride, dilithium telluride and disodium selenide to chloromethyl alkynyl sulfides and tellurides give a variety of 1,3-dichalcogenoles as shown in Scheme 15 (81RTC10,82TL1531>. The preparation of the 1,3-ditelluroles required the use of dilithium telluride under carefully controlled conditions. 

Treatment of alkynyl sulfides 347 with KOBu gives 2,3-dihydrothiophenes 351. The reaction might involve S-end-r/tg cyclization of intermediates 348, 349, and/or 350 (Scheme 59) <2000TL5637>. 

S -Analogues of lithium or sodium ynolates (thioalkynolates or alkynethiolates) are prepared from lithium or sodium acetylide and sulfur, and are trapped as alkynyl sulfides with bromoethane (equation 77). In a synthetic approach analogous to equation 72, 5-lithio-l,2,3-thiadiazoles (198) also afford lithium alkynethiolates (199) by elimination of nitrogen (equation 78) . Alkynyl sulfides (200) are treated with lithium in ammonia to afford lithium alkynylthiolates (199) (equation 79) °. Theoretical studies on the structure of alkali metal alkynylthiolates are reported. ... 

Nucleophilic reactions of lithium thioalkynolates with electrophiles mostly occur at the 3 -position to afford alkynyl sulfides. For example, 3 -silylation and 3 -stannation are shown in equation 80 the synthesis and -alkylation of a quaternary ammonium thioalkynolate are shown in equation 81. Exceptionally, lithium thioalkynolates add to ketones to form -thiolactones, which are converted into alkenes on elimination of carbon oxysulfide (equation 82). Contrary to lithium ynolates, thioalkynolates do not react with aldehydes. ... 

The chiral titanium reagent (6) also catalyzes the [2 + 2] cycloaddition reaction of 1,3-oxazolidin-2-one derivatives of a,(3-unsaturated carboxylic acids and ketene dithioacetals in the presence of MS 4A to give cyclobutanone dithioacetal derivatives with high optical purity (eq 10). Vinyl sulfides, alkynyl sulfides, and 1,2-propadienyl sulfides can also be employed in this reaction to give the corresponding cyclobutanes, cyclobutenes and methylenecyclobutane derivatives with high optical purity (eqs 11 and 12). ... 

Cycloaddition Reactions of Imines with Alkynyl Sulfides... 

Metallation of various 1-alkynyl sulfides, followed by alkylation of the resulting anion leads exclusively to a-alkylated allenyl sulfides (Scheme 39). 

Reaction with alkynes. (f-Butyldimethylsilyl)alkynes give dimers while simultaneously introducing one or two iodine atoms into the products. Certain alkynyl sulfides undergo cyclization. ... 

Thiol esters. Hydration of alkynyl sulfides gives thiol esters (7 examples, 51 -86%). TsOH can be used instead of CFjCOOH. 

As is shown in Scheme 6 and Table 1, alkynyl sulfides can be employed in the asymmetric [2-1-2] cycloaddition reaction however, the reactivity of alkynyl sulfides is largely dependent on the substituent at sulfur. A phenyl sulfide, 1-phenylthio-l-hexyne (5e), does not react with 2a, while the alkynyl methyl sulfides 5a-d react smoothly with fumaric and acryUc acid derivatives 2a,c, yielding cyclobutenes 6. Trisubstituted cyclobutenes are prepared in good yield and in almost enantiomerically pure forms with only a catalytic amount of the chiral titanium reagent. For the preparation of tetrasubstituted cyclobutenes, however, an equimolar amount of the chiral titanium is required for the reaction to go to completion. Compared with the ketene dimethyldithioacetal 3a, alkynyl methyl sulfides 5 are less reactive and the reaction between the crotonoyloxazo-lidinone 2b and 5 fails even in the presence of an equimolar amount of the catalyst. 

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