Sulfoxides, aryl vinyl

Aryl vinyl sulfides and sulfoxidesArylsulfenyl chlorides add to trimethyl vinyl-silane in CH2CI2 at -78 - 20° to form 2-chloro-l-(trimethylsilyl)ethyl aryl sulfides in 90-95% yield. These adducts are converted into aryl vinyl sulfides in high yield by KF-2H20 DMSO at 70 100°. The sulfides, as expected, can be oxidized to the corresponding sulfoxides by m-chlo roper benzoic acid in CH2C12 at 20". 

Allyl sulfoxide systems appropriate for a transformation to allylic alcohols can also be generated by other preparative methods, e.g. by isomerization of aryl vinyl sulfoxides. Such an isomerization occurs in connection with a Knoevenagel reaction of (10) with aldehydes leading finally to y-hydroxy-a,3-unsatu-rated systems (11), which can easily be transformed into a,3-unsaturated y-lactones (12 Scheme 17). ... 

Hoffmann has used an isomerization of readily available aryl vinyl sulfoxides, which can be obtained in optically active form, to study the possibility of generating optically active allyl alcohols by employing chirality transfer from sulfur to carbon. While this synthetic route (Scheme 18) to allylic alcohols generally works well and gives good yields, the optical yields which could be obtained are only satisfactory in some cases, e.g. (/ )-(Z)-sulfoxide (13) gave the (S)-(+)-octenol (14) with greater than 80% optical purity, whereas the (/ )-( 5-isomer (15) yielded only 29% of the (f )-(-)-enantiomer (16 Scheme 19). 

Lithiated allylic sulfoxides may be a-alkylated and the resulting products subjected to [2,3]-sigmatropic rearrangement induced by a thiophile to give allylic alcohols (eq 43). In contrast, alkenyl aryl sulfoxides produce a-lithiated species which are alkylated with Mel or PhCHO in good yields (eq 44). LDA has also been used to metalate allylic and propargylic selenides as weU as aryl vinyl selenides. ... 

The reaction is of the 8 2 type and works best with primary and secondary alkyl halides Elimination is the only reaction observed with tertiary alkyl halides Aryl and vinyl halides do not react Dimethyl sulfoxide is the preferred solvent for this reaction but alcohols and water-alcohol mixtures have also been used... 

Abbreviations aapy, 2-acetamidopyridine Aik, alkyl AN, acetoniuile Ar, aryl Bu, butyl cod, 1,5-cyclooctadiene COE, cyclooctene COT, cyclooctatetraene Cp, cyclopentadienyl Cp , penta-methylcyclopentadienyl Cy, cyclohexyl DME, 1,2-dimethoxyethane DME, dimethylformamide DMSO, dimethyl sulfoxide dmpe, dimethylphosphinoethane dppe, diphenylphosphinoethane dppm, diphenylphosphinomethane dppp, diphenylphosphinopropane Et, ethyl Ec, feirocenyl ind, inda-zolyl Me, methyl Mes, mesitylene nb, norbomene orbicyclo[2.2.1]heptene nbd, 2,5-norbomadiene OTf, uiflate Ph, phenyl PPN, bis(triphenylphosphoranylidene)ammonium Pi , propyl py, pyridine pz, pyrazolate pz, substituted pyi azolate pz , 3,5-dimethylpyrazolate quin, quinolin-8-olate solv, solvent tfb, teti afluorobenzobaiTelene THE, tetrahydrofuran THT, tetrahydrothiophene tmeda, teti amethylethylenediamine Tol, tolyl Tp, HB(C3H3N2)3 Tp , HB(3,5-Me2C3HN2)3 Tp, substituted hydrotiis(pyrazol-l-yl)borate Ts, tosyl tz, 1,2,4-triazolate Vin, vinyl. 

Lithiochloromethyl phenyl sulfoxide 99 was found to react with aryl or alkyl halides in the presence of one equivalent of hexamethylphosphoramide to afford alkylated products 100 in high yields135. Thermal decomposition of these products in the presence of a catalytic amount of hydroquinone in xylene gave the corresponding vinyl compounds 101. 

Carboxylation of lithiated vinylic sulfoxides is also highly stereoselective, as shown by a one-pot experiment leading from optically pure (if)- -alkenyl aryl sulfoxides to optically pure methyl 2-arylsulfinyl-2-alkenoates without EjZ isomerization63. 

Bromination of the enol ether product with two equivalents of bromine followed by dehydrobromination afforded the Z-bromoenol ether (Eq. 79) which could be converted to the zinc reagent and cross-coupled with aryl halides [242]. Dehydrobromination in the presence of thiophenol followed by bromination/dehydrobromination affords an enol thioether [243]. Oxidation to the sulfone, followed by exposure to triethylamine in ether, resulted in dehydrobromination to the unstable alkynyl sulfone which could be trapped with dienes in situ. Alternatively, dehydrobromination of the sulfide in the presence of allylic alcohols results in the formation of allyl vinyl ethers which undergo Claisen rearrangements [244]. Further oxidation followed by sulfoxide elimination results in highly unsaturated trifluoromethyl ketonic products (Eq. 80). 

Cycloaddition with nitrile oxides is also efficient with trisubstituted enol ethers and enolates. With fluoro-substituted chiral vinyl sulfoxides 10. cycloadditions performed with aryl chloroaldoximes, at room temperature in carbon tetrachloride in the presence of triethylaminc, are slow but give the homochiral dihydroisoxazoles 11 with high regio- and diastereoselectivity. ... 

Chiral vinyl sulfoxides have been prepared by a Wittig Horner reaction of chiral (R)- or (.Si-dimethyl (4-tolylsulfinyl)methanephosphonate with carbonyl compounds3-66,67. For acyclic systems reprotonation of the anions from vinyl sulfoxides gave a mixture of E- and Z-isomers3, whereas isomerization of an exocyclic double bond in a ring system provided access to chiral aryl 1-cycloalkenylmethyl sulfoxides66-67. 

Chiral vinyl sulfoxides have been coupled to aryl iodides to give a chiral allylic aryl compounds (C=C-CH2—Ar), in a three-step procedure with good enantio-selectivity. ... 

The method employing the sequential alkylation and elimination of sulfoxides, reported above, has been successfully applied to the synthesis of dienes (Scheme 86, entry c), aryl alkenes and dienes (Scheme 47), vinyl sulfides, a,3-unsaturated sulfoxides, vinyl fluorides and vinyl chlorides (Scheme 96, entry a), and 1,1-dichloro-l-alkenes (Scheme 96, entry b). ... 

---