Diyne sulfides

Di- and tetraynes with hydrogen sulfide in an alkaline medium at 20-80°C form systems containing linked thiophene cycles. Thus, l,4-dithienylbuta-l,3-diyne (47) forms 2,5-di(2-thienyl)thiophene (48) in 78% yield, whereas octa-2,4,6-tiiyn-l-ol (49) under the same conditions gives 5-hydroxymethyl-2-prop-1-ynylthiophene (50) in 50% yield (77HOU947). 

DITHIENYL SULFIDE, 50 75 1,3-Dithiolanes, 54, 37 Diynes, preparation, 50, 101 n-Dodecane, 53, 108 Double bond, exocyclic, selective hydrogenation, 53, 65 DURENE, I0D0—, 51, 94... 

An interesting reaction course was followed in the case of dipropargyl amides and dipropargyl sulfide. With these diynes, in fact, triple bond insertion into the Pd - C bond of an alkoxycarbonylpalladium complex was followed by insertion of the second triple bond and alkoxycarbonylation (Scheme 35) [303,... 

DITHIENYL SULFIDE, 50, 75 Diynes, preparation, 50, 101 DURENE, IODO-, 51, 94... 

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>. 

Thiols very readily add to diacetylene in the presence of bases, such as alkoxides, with formation of enyne sulfides HC=CCH=CHSR [175]. In strongly basic media, thiol can be eliminated from these enyne derivatives [2], Thus, functionalization of HChCCH=CHSR followed by treatment with an excess of sodium amide results in a derivative of butadiyne. This sequence of conversions permits the synthesis of some 1,3-diyne systems that are not otherwise easily accessible. 

Reaction of a four-carbon unit with sulfur sources such as hydrogen sulfide, carbon disulfide, and elemental sulfur is one of the traditional thiophene syntheses that belong to this category (Equation 18). A wide variety of hydrocarbons, for example, alkanes, alkenes, dienes, alkynes, and diynes, serve as four-carbon units. Another practical method is the sulfuration of 1,4-dicarbonyl compounds (Paal synthesis). The method has become very popular with development of sulfuration reagents such as Lawesson s reagent. The reaction of a,/3-unsaturated nitriles with elemental sulfur in basic media, Gewald synthesis, is also useful for the preparation of 2-aminothiophenes which are important compounds in dyestuff and pharmaceutical industries. 

This sequence, for the regioselective synthesis of 2,2 5, 3"-terthiophene uses the reaction of a diyne with sodium sulfide to make the central ring. ... 

Recently, the PE spectra of a number of l,6-dihetero-cyclodeca-3,8-diynes have been investigated. The splitting of the four 7r-bands nt,7ti,Uo and tiq has been found to occur in the range of 1.2-1.6 eV. In figure 16 we show a correlation of the first PE bands of 55-60 As anticipated, in the PE spectrum of dipropynyl sulfide (61) the signals for the triple bonds are hardly split. ... 

Much use has been made of conjugated diynes, also at the oxidation level of 1,4-dicarbonyl compounds, which react smoothly with hydrosulfide or sulfide, under mild conditions, to give 3,4-unsubstituted thiophenes. Unsymmetrical 2,5-disubsti-... 

Addition of carbon disulfide to the carbanion, generated from the allene (13), and intramolecular addition of the dithiocarboxylate sulfur to the triple bond gives the compoimd (14) (Scheme 5) <85TL5I31>. Metallation of the diynes (15), followed by the successive addition of carbon disulfide, Bu OH, and HMPT, affords thienothiophenes (17) in reasonable yields (Scheme 6), and the use of the sulfides (18) as the starting material produces the thienodithiins (19) (Equation (3)) when R is TMS in the starting compounds, the unsubstituted parent compounds are obtainable in these cases since desilylation probably takes place at some intermediate stage <83CC1056>. 

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