Thiolene reaction

The addition of thiols to olefins (thiolene reaction), to form thioethers, is a well-known reaction. The process can occur by either free-radical or ionic mechanisms. The free-radical reaction can be initiated thermally via a peroxide or by UV irradiation with benzophenone. The initiation step involves the formation of a thiyl radical by hydrogen atom abstraction. Both of these species are capable of starting polymer chains (Table 2.30). 

E.K. Skinner, F.M. WhifEn, G.J. Price, Room temperature sonochemical initiation of thiolene reactions. Chem. Commun. 48,6800-6802 (2012)... 

The hydroxythiophenes which exist predominantly as the thiolen-2-ones also show reactions characteristic of the enol form. They can be methylated at the oxygen with dimethyl sulfate of diazomethane and they can also be acylated. - - They also react as thio-lene-2-ones showing a reactive methylene group which can be condensed with benzaldehyde. The danger of using chemical reactivity data for drawing conclusion as to the physical state of these tautomerizable systems has been pointed out. ... 

Thus the reaction of the three geometrical isomers of 2,4-hexadiene with thiirane oxide afforded the three related 3-thiolene 5-oxides 154 depicted in equation 62104... 

Since sulfoxides and sulfones are versatile synthetic intermediates, and since in both the thiolene oxide and dioxides the reverse dethionylation114 ( — SO), and cheletropic extrusion of sulfur dioxide296, respectively, readily take place thermally, these cycloadditions are expected to find a useful place in organic synthesis. It should be kept in mind, however, that the retrograde SO-diene reaction and interconversion of the thiolene oxides compete effectively against SO extrusion on heating, and that diene isomerization accompanies the forward reaction (SO + diene). 

Thio-Claisen rearrangement 746-748 Thioketene 5-oxides photolysis of 878 reactions of 277 Thiolane dioxides formula of 382 NMR spectra of 460 reactions of 604 synthesis of 461 Thiolane oxides 747 formula of 382 IR spectra of 461 synthesis of 461, 462, 752 Thiolanes, photolysis of 881 Thiolene dioxides formula of 382 NMR spectra of 460 reactions of 464, 465 synthesis of 461 Thiolene oxides formula of 382 synthesis of 461, 746 Thiols... 

The first reactions were carried out at room temperature in devices fabricated from a thiolene resin cured between two glass slides. 2-Hydroxypropyl methacrylate (HPMA) was polymerized by ATRP, and reaction kinetics similar to those obtained in a traditional batch reaction were obtained by adjusting the total flow rate of the fluid through the channel and treating the residence time in the channel as the reaction time (Fig. 21b,c) [102]. 

The correlation of residence time to reaction time is critical in the ability to treat the volume of the channel as a continuous gradient in molecular mass. ATRP is particularly well-suited to this type of device because the reaction can be initiated at a fixed mixing element at the head of the channel where a catalyst and initiator can be brought together. By replacing a small molecule initiator with a polymer chain capable of being reinitiated, copolymers could be prepared. This was done in the thiolene/glass devices with a poly(n-butyl methacrylate) block... 

Fig. 21 Representative microfluidic device and resulting data from ATRP on a chip a image of a microfluidic device (dimensions 25 mm x 75 mm) fabricated from UV curable thiolene resin between two glass slides b reaction data for ATRP of HPMA synthesized on a chip showing the correlation of flow rate (or residence time) to reaction time and resulting conversion of monomer (M) to polymer (ln([M]o/[M]) c comparison of number average molecular mass (M ) and poly-dispersity for -butyl acrylate prepared in a traditional round bottom flask ( Flask ) and on a chip ( CRP Chip ). (Reproduced with permission from [102])...

Treatment of the substituted aminosulfolene (253) with phenyl isothiocyanate in refluxing benzene-pyridine (2 1) gave the perhydrothieno[3,4-rf]imidazole-2-thione 5,5-dioxide (254) (82CHE328). Reaction of 4-halo-2-thiolene (or -thiolane) 1,1-dioxides with dithiocarbamates proceeded similarly to give perhydrothieno[3,4-[Pg.1011]

Five membered ring sulfones (thiolene-1, 1-dioxides, sulfolenes or dihydrothiophene-1, 1-dioxides) can be obtained by peracid oxidation of tetrahydrothiophene. The extrusion of sulfure dioxide from dihydrothiophene-1,1 dioxides or sulfolenes like (178) has been much studied as it provides a synthetic route to dienes, e.g. butadiene (152) (Scheme 70). The reverse reaction provides a method of synthesis of sulfolene (178) from butadiene (152) and sulfur dioxide. Thiolene dioxides or sulfolenes can be generally prepared by addition of sulfur dioxide to conjugated dienes for example, 1,4-dimethylbutadiene (179) in the presence of sulfure dioxide, triethylamine and formic acid affords 2,5-dimethylsulfolene (180) (Scheme 71). 

There are relatively few reports involving the Michael addition of cyanomethylphosphonate anions to unsaturated compounds. The reaction provides a methodology for the elaboration of new reagents but more frequently is used for the preparation of phosphonylated heterocycles. Under basic conditions, diethyl cyanomethylphosphonate adds to benzalacetophenone and 2-bcnzylidcne-3-methyl-4-nitro-3-thiolene-l,l-dioxide to give the addition products in modest yields.- - - " ... 

Nikolaenko, T.Y., Trukhin, E.V., Tebbi, J., and Berestovitskaya, V.M., Reaction of phosphorylated CH acids with 2-bcnz.ylidcne-3-inethyl-4-nilro-3-thiolene 1,1-dioxide, Zh. Obshch. Khim., 66, 1043, 1996 Russ. J. Gen. Chem. (Engl. Transl.), 66, 1018, 1996. 

KCoF4,63,64 with potassium hydroxide65,66 (Scheme 3). Tetrafluorothiophene (11) has also been prepared by a route involving a final dechlorination step using zinc (Eq. 15)67 and 2,5-difluorothiophene (13) by the unusual defluorination of 2,2,5,5-tetrafluoro-3-thiolene (12) over sodium fluoride.68 Perfluorobenzofuran (15) can be prepared by reaction of benzofuran (14) with CsCoF4, followed by defluorination with nickel.69... 

The Structures and Reactions of Hydroxy-, Mercapto-, and Aminothiophens. - 3-Thiolen-2-one reacts as dienophile with... 

In the latter case, some (118) was also formed. The reaction of 3-thiolen-2-one with 1,3-cyclopentadiene proceeded rapidly at room temperature in the presence of boron trifluoride etherate, to give (119). An exception was the reaction with 1-methoxy-3-C(trimethyls ilyl)oxy]butadiene, which only led to silyl transfer, giving 2-(trimethylsiloxy)thiophen and 4-methoxy-but-3-en-2-one.6 The reaction between the ambient anion of the 5-methyl-2-hydroxy-thiophen system with carbon disulphide and methyl iodide gave (121) in 36% yield, in addition to the expected product (120). Tfie structure of the latter compound was proven by X-ray crystallography, and a reaction path for its formation was suggested. The... 

Since "normal" thiolene polymerizations are well known not to be inhibited by the presence of oxygen, we also focused our model study on the nature of the interaction of norbornene, thiol, and oxygen. When the addition-cooxidation reaction of thiophenol and norbornene is catalyzed by slowly bubbling air through the reaction mixture, two products are obtained. The major product (ca. 60%) is the expected addition product exo—2-thiophenylnorbornane (from cis-exo addition of PhS and H). The other product is the cooxidation product, exo-2-phenylsulfinyl-e eO"3-hydroxjmorbornane (Figure 5). 

The preceding study has demonstrated [2.2.1]bicycloheptenyl functionalized resins can be useful and interesting ene components in photoinitiated thiolene polymerizations. The addition of thiols to the unsaturation of this bicyclic system appears to be rapid and exothermic. The relative rates of this addition compared with allylic derivatives and vinyl ethers are quite favorable. The organic resins can be readily prepared from either polyols, f>olyamines, or acrylic precursors (Figure 10) and the yields are generally quite good. When acrylate esters are used as precursors, the cycloaddition reaction occurs spontaneously and no catalysis of the reaction is necessary. 

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