Thiols from olefins

The reaction under consideration is typified by the formation of saturated carboxylic acids from olefins, carbon monoxide, and water. Other compounds have been used in place of olefins (alkyl halides, alcohols), and besides water, a variety of compounds containing active hydrogen may be employed. Thus, alcohols, thiols, amines, and acids give rise to esters, thio-esters, amides, and acid anhydrides, respectively (15). If the olefin and the active hydrogen are part of the same molecule, three or four atoms apart, cyclizations may occur to produce lactones, lactams, imides, etc. The cyclizations are formally equivalent to carbonylations, however, and will be considered later. 

In our laboratory, we prepared several difunctional products from addition of thiols onto olefines [16] ... 

Examples of alkylation, dealkylation, homologation, isomerization, and transposition are found in Sections 1, 17, 33, and so on, lying close to a diagonal of the index. These sections correspond to such topics as the preparation of acetylenes from acetylenes carboxylic acids from carboxylic acids and alcohols, thiols, and phenols from alcohols, thiols, and phenols. Alkylations that involve conjugate additions across a double bond are found in Section 74 (alkyls, methylenes, and aryls from olefins). 

Hydroperoxides have been isolated from the systems [94,95], even though they react readily with excess thiol. Mono-olefins were found to lead to 2-sulphinyl-ethanol secondary products [95], while the secondary products of di-olefins depended on the relative reactivity of the two double bonds [96]. An interesting review of the detailed chemistry involved in recognising the reaction mechanism is given by Oswald and Wallace [97] some of the more pertinent details are discussed below. 

The functional group conversion is taken as the independent variable, the reaction kinetics of the ring-free thiol-ene system is expected to be identical to that of usual step-growth reactions. In the rate expressions for intermolecular reactions in thiol-enes are first-order reactions overall. The cyclization rate in thiol-ene reactions is slower compared to that in step-growth reactions. This result arises from intramolecular chain transfer reactions reducing the probability of favorable intramolecular collisions between the functional groups. Some examples of thiols and olefins are listed in Table 3.3. 

A new and elegant solvent-free approach to main chain LCEs was found by Yang et al. [39] who, based on the work on linear LC polymers by Lub et al. [40 2], made use of the photo-induced addition of thiols and olefins (click-chemistry) to synthesize nematic polymer networks. Starting from a mixture of the mesogen, a tetrafunctional crosslinker and a photo-initiator networks with a around 170 °C were obtained by UV crossUnking (Scheme 8). 

General Reaction Chemistry of Sulfonic Acids. Sulfonic acids may be used to produce sulfonic acid esters, which are derived from epoxides, olefins, alkynes, aHenes, and ketenes, as shown in Figure 1 (10). Sulfonic acids may be converted to sulfonamides via reaction with an amine in the presence of phosphoms oxychloride [10025-87-3] POCl (H)- Because sulfonic acids are generally not converted directiy to sulfonamides, the reaction most likely involves a sulfonyl chloride intermediate. Phosphoms pentachlotide [10026-13-8] and phosphoms pentabromide [7789-69-7] can be used to convert sulfonic acids to the corresponding sulfonyl haUdes (12,13). The conversion may also be accompHshed by continuous electrolysis of thiols or disulfides in the presence of aqueous HCl [7647-01-0] (14) or by direct sulfonation with chlorosulfuric acid. Sulfonyl fluorides are typically prepared by direct sulfonation with fluorosulfutic acid [7789-21-17, or by reaction of the sulfonic acid or sulfonate with fluorosulfutic acid. Halogenation of sulfonic acids, which avoids production of a sulfonyl haUde, can be achieved under oxidative halogenation conditions (15). 

This reaction is based on a stoichiometric reaction of multifunctional olefins (enes) with thiols. The addition reaction can be initiated thermally, pho-tochemically, and by electron beam and radical or ionic mechanism. Thiyl radicals can be generated by the reaction of an excited carbonyl compound (usually in its triplet state) with a thiol or via radicals, such as benzoyl radicals from a type I photoinitiator, reacting with the thiol. The thiyl radicals add to olefins, and this is the basis of the polymerization process. The addition of a dithiol to a diolefin yields linear polymer, higher-functionality thiols and alkenes form cross-linked systems. 

Under the usual commercial hydrodesulfurization conditions (elevated temperatures and pressures, high hydrogen-to-feedstock ratios, and the presence of a catalyst), the various reactions that result in the removal of sulfur from the organic feedstock (Table 4-3) occur. Thus, thiols as well as open chain and cyclic sulfides are converted to saturated and/or aromatic compounds depending, of course, on the nature of the particular sulfur compound involved. Benzothio-phenes are converted to alkyl aromatics, while dibenzothiophenes are usually converted to biphenyl derivatives. In fact, the major reactions that occur as part of the hydrodesulfurization process involve carbon-sulfur bond rupture and saturation of the reactive fragments (as well as saturation of olefins). 

Ivlixed inhibitors may simultaneously affect both anodic and cathodic processes. A mixed inhibitor is usually more desirable because its effect is all-encompassing, covering corrosion resulting from chloride attack as well as that due to microcells on the metal surface. Mixed inhibitors contain molecules in which electron density distribution causes the inhibitor to be attracted to both anodic and cathodic sites. They are aromatic or olefinic molecules with both proton-forming and electron acceptor functional group such as NH or SH, as in aminobenzene thiol. Mixed inhibitors are similarly used at l-2 > addition rates [50],... 

Saturated and unsaturated hydrocarbons (Figure 6C) of the pyrolysate are largely dominated by straight-chain hydrocarbons ranging from C14 to C32. There is a drastic drop of concentration of saturated and unsaturated hydrocarbons after the C30 monoenes elutes. The C28, C29, C30 olefins are dominant with their diolefinic counterparts. The FPD trace of the "intermediate" fraction of the pyrolysate (Figure 6D) is dominated by a C30 n-alkylthiophene and by a C30 n-alkylthiolane-thiol tentatively identified from mass spectra. The n-alkylthiophenes dominate throughout the fraction with a distribution ranging from C13 to C32. The C28-C30 are the most prominent thiophenes. The presumed C28-C30 thiolane-thiols show the same distribution as the C28-C30 thiophenes. 

One of the reported syntheses of ( )-9-oxodec-2-enoic acid 392, the queen substance of the honey bee Apis mellifera, uses two ylide reactions 222). Starting from pimelic acid 385 the resonance-stabilized ylide 386 is prepared by alkylation of methylene-triphenylphosphorane 209 and the former hydrolyzed to 7-oxooctanoic acid 387. Reduction of the corresponding thiol ester 389 and olefination of the resulting aldehyde 390 with phosphorane 67 gives the ( )-2-unsaturated ester 391. The latter was hydrolyzed to pheromone 392 222) (Scheme 69). 

Examples of name reactions can be found by first considering the nature of the starting material and product. The Wittig reaction, for instance is in Section 199 (olefins from aldehydes) and Section 207 (olefins from ketones). The aldol condensation can be found in the chapters on difunctional compounds in Section 324 (alcohol, thiol-aldehyde) and in Section 330 (alcohol, thiol-ketone). 

Classification and Organization of Reactions Forming Difunctional Compounds. This chapter considers all possible difunctional compounds formed from the groups acetylene, carboxylic acid, alcohol, thiol, aldehyde, amide, amine, ester, ether, epoxide, thioether, halide, ketone, nitrile, and olefin. Reactions that form difunctional compounds are classified into sections on the basis of the two functional groups of the product. The relative positions... 

De Clercq [38] has utilized a sulfide linker, cleaved by a radical process initiated by electron transfer, in a solid-phase Julia-type olefination process. Alkylation of an aryl thiol resin followed by mCPBA oxidation gave supported sulfone 217 (Scheme 54). Successive treatment of the resin with n-butylhthium and an aldehyde followed by trapping of the resultant alkoxide with benzoyl chloride gave resin-bound a-benzoyloxy sulfone 218. Olefins 219 and 220 were released from the sohd support upon reduction with a single-electron-transfer reagent and elimination of the sulfone link-... 

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