Synthesis alkenyl sulfides

The thioboration of terminal alkynes with 9-(alkylthio)-9-borabicyclo[3.3.1]-nonanes (9-RS-9-BBN) proceeds regio- and stereoselectively by catalysis of Pd(Ph,P)4 to produce the 9-[(Z)-2-(alkylthio)-l-alkeny)]-9-BBN derivative 667 in high yields. The protonation of the product 667 with MeOH affords the Markownikov adduct 668 of thiol to 1-alkyne. One-pot synthesis of alkenyl sulfide derivatives 669 via the Pd-catalyzed thioboration-cross-coupling sequence is also possible. Another preparative method for alkenyl sulfides is the Pd-catalyzed cross-coupling of 9-alkyl-9-BBN with l-bromo-l-phe-nylthioethene or 2-bromo-l-phenylthio-l-alkene[534]. 

A similar strategy can be applied to intramolecular systems for the synthesis of cyclic alkenyl sulfides37 (Scheme 25). Instead of chloroalkyl sulfides 82, dithioacetals 83 can be used more effectively as the precursor of thiocarbenes... 

Trisubstituted alkenes.9 A stereoselective synthesis of trisubstituted alkenes uses (E)-alkenyl sulfoxides (1)>U as the starting material. These are reduced to the corresponding sulfides (2)," which undergo coupling with Grignard reagents in the presence of complexes of nickel chloride and phosphines as catalyst.12 The products (3) are obtained in steroisomeric purity of > 99%. 

Synthesis of alkenyl sulfides and ketenedithioacetals from thiolesters and dithiocarbonates... 

Another way of synthesis of ketencdithioacetals and of alkenyl sulfides makes use of an alkylidenation of dithiocarbonates or thiolesters with a reagent introduced by Takai [439] and prepared from R CHBr2, Zn, TiCl4 and TMEDA (Table 4.4). 

Nucleophilic substitution of a,/3-epoxysilanes followed by the Peterson elimination is valuable for the stereoselective synthesis of alkenes.3 The reactions with lithium phenylsulfide and diphenylphosphide form alkenyl sulfides and alkenylphosphines, respectively, in a stereospecific manner. 7-Metallo-a,/ -epoxysilanes are isomerized to a-siloxyallylmetals by anionic ring opening and subsequent Brook rearrangement (Equation... 

Murahashi, S., Yamamura, M., Yanagisawa, K., Mita, N., Kondo, K. Stereoselective synthesis of alkenes and alkenyl sulfides from alkenyl halides using palladium and ruthenium catalysts. J. Org. Chem. 1979,44, 2408-2417. 

Synthesis of alkenyl sulfides and ketencdithioacctals from thiolesters and dithiocarbonatcs... 

Diquinane synthesis. 2-(4-Alkenyl)cyclopropyl sulfides are Uansformed into diquinanes on oxidation with tris(4-bromophenyl)aminium ions in dichloromethane at room temperature. 

An efficient synthesis of variously substituted 2,3-dihydrothiophenes was developed that involved a copper-catalyzed S-alkylation and S-alkenyl-ation of sodium sulfide with 1,4-diiodoenes to yield 2,3-dihydrothiophenes in high yields (13TL1475). The 2,3-dihydro derivatives were converted to the appropriate thiophene by oxidation. 

A rhodium synthesis of sulfenylated imines containing a quaternary centre has been reported through a denitrogenative [2,3]-sigmatropic rearrangement of 4-aryl-, 4-alkenyl-, and 4-alkyl-A-sulfonyl-l,2,3-triazoles with aryl (alkyl)allyl sulfides (Scheme 57)7 ... 

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