Thiophenol, reaction with esters

Thiol protection, 59, 190 Thiono esters, reaction with ethyl isocyanoacetate, 59,187 Thionyl chloride, 55, 27 Thiophenol, 55, 122 58, 144 Thorium dodecanedioate, 56,110 Toluene, 56, 86 58,125 p-Toluenesulfonates, reaction with organo-cuprates, 55,112 p-Toluenesulfonic acid, 58, 57, 63 p-Toluenesulfonic acid, monohydrate, 56,44... 

Trimethylsilyl esters of tris(thio)phosphonic acids 2070 are readily oxidized by DMSO in toluene at -30 °C to give the dimeric tetra(thia)diaphosphorinanes 2071 and HMDSO 7 [208] (cf. also the oxidation of silylated thiophenol via 2055 to diphenyl disulfide). The polymeric Se02 is depolymerized and activated by reaction with trimethylsilyl polyphosphate 195 to give the corresponding modified polymer... 

Imidoyl esters (Scheme 3.7) are obtained readily when the appropriate imidoyl chloride is reacted with an alcohol or phenol under basic conditions in the presence of phase-transfer catalysts [71]. The reaction with thiophenol yields the corresponding thioimidoyl ester. Diaroyl amides are produced by the analogous reaction of the imidoyl chloride and carboxylate anions. In this reaction, the initially formed carboxylic ester undergoes a 1,3-migration to produce the amide. 

The reactivity of seven resin-bound thiophenol esters toward n.-butylamine (41) varied depending on their structures. The reaction of aromatic thiophenol esters (resins (34-36) took about 24 h to complete as indicated by the complete disappearance of carbonyl band in single bead FTIR spectra. On the other hand, the same reaction with alkyl thiophenol esters (resins 38-40) went to completion in less than 8 hours. The reaction with benzimidazolecarboxylic thiophenol ester (resin (37) was the fastest, finished in 3 h. 

It is not surprising that chloro esters 1, 2 readily add thiols, catalyzed by sodium thiolates or triethylamine, to give the corresponding 2-(r-organylthiocy-clopropyl)-2-chloroacetates 85,86 (Scheme 22) [15 b, 22b, 27]. This reaction with thiophenol has been used to quantify the Michael reactivity of 1-Me, 2-Me, 3-X in comparison to simple acrylates (see above). With an excess of PhSH, the nucleophilic substitution of the chlorine in 85 a (but not in 85h) proceeded to give the corresponding bis(phenylthio) derivative in 63% yield [15bj. Alkali thiolates (e.g. NaSMe, NaSBn) add smoothly onto 1-Me, 2c-Me and 2p-Me at - 78 °C, because at this temperature subsequent nucleophilic substitution of the chlorine is much slower [7l, 9]. The Michael additions of sodium phenylselenide and sodium arylsulfenates onto 1-Me and their synthetic utility have been discussed above (see Table 1). 

The Michael-aldol process with methacrylates described in Section II.B can be also applied to the synthesis of substituted tetrahydrofurans, 245. If the reaction is carried out in THF, the yield and selectivity of the sequence decrease. It was proposed that the lithium coordination with THF molecules hinders the formation of the product 245. The authors concluded that the Lewis acidity of naked lithium cation is the key driving force for the reaction to proceed successfully. The tandem reaction with lithium thiophenolate, fumarate ester and benzaldehyde constitutes an useful methodology for the preparation of y-butyrolactone (Scheme 75)89,90. 

Sodium enolates of ketones and disodium enediolates of substituted phenylacetic acids reacted with activated aziridines to afford 7-amido ketones and 7-amidobutyric acids, respectively (Scheme 72). Aziridine-2-carboxylic acid esters can be utilized as versatile precursors for amino acid derivatives. Although the product distribution resulting from the reaction of activated aziridine-2-carboxylates with amines depends on the structure of the reactants, the reactions with alcohols or thiols in the presence of acidic cabilysts generally gave the a-amino acid derivatives (Scheme 73). ° On the other hand, free 3-methyl-2-aziridinecarboxylic acids (168) reacted with thiophenol, cysteine and glutathione to afford P-amino acid derivatives with sulfur substituents at the a-position as the main product (Scheme 73). ... 

The acid chlorides specified in reaction (1) may be replaced by 5-esters of thiocarboxylic acids [i.e., RC(0)SC6H5 or RC(0)SC2H5 in place of RCOC1] 458 their reaction leads to separation of a thiophenol or an alkane-thiol, and these products do not consume a second molecule of the alkylidenephosphorane. The last statement is true also for the reaction with 1-acylimid-azoles described by Bestmann, Sommer, and Staab.459... 

The chemical reactivity of [Rh l6)] was also examined in reactions with H-atom donors, where the complex behaves as a nucleophilic radical [90]. The reaction rates were dependent on the X-H bond dissociation energies, reacting rapidly with staimane (BusSn-H) and thiophenol, more slowly with ferf-butyl thiol and thioglycolic acid methyl ester and not at all with phenol and triphenylsilane [90]. 

Polarographically-inactive alcohols or phenols, mercaptans and thiophenols could be transformed by reaction with 3,5-dinitrobenzoic acid into polarographically-active 3,5-dinitrobenzoic acid esters (see Figure 6). 

Catalysts 1 and 4 are reported to give the best results for the conjugate addition of thiophenol to 2-phenylacrylates (Scheme 6.2) [17]. The products were obtained with opposite enantioselectivity in the reaction with 1 and 4, respectively, as the catalyst. Based upon a computational analysis, it was proposed that the transition state for the reaction involves hydrogen bonding between the hydroxy group of the catalyst and the carbonyl group of the ester and asymmetric proton transfer from the thiol to enolate anion (Scheme 6.2). 

Carboxylic acids such as acetic acid react with alcohols such as methanol or with methoxytrimethylsilane 13 a in the presence of trimethylchlorosilane (TCS) 14 in THF or 2-methyl-THF to give esters such as methyl acetate in 97% yield and hex-amethyldisiloxane 7. Even methyl pivalate can be readily prepared in 91% yield [111]. Reaction of a variety of carboxylic acids, for example N-benzoylglycine 329, with two equivalents of yS-trimethylsilylethanol 330 and with 14 has been shown to afford esters such as 331 in 98% yield [112, 112 a]. Likewise, silylated carboxylic acids react with silylated alcohols or thiophenols in the presence of 4-trifluoro-methylbenzoic anhydride and TiCl4/AgCl04 to furnish esters or thioesters in high yields [113, 114] (Scheme 4.43). 

Among the most useful radical fragmentation reactions from a synthetic point of view are decarboxylations and fragmentations of alkoxyl radicals. The use of (V-hydroxy-2-thiopyridine esters for decarboxylation is quite general. Several procedures and reagents are available for preparation of the esters,353 and the reaction conditions are compatible with many functional groups.354 f-Butyl mercaptan and thiophenol can serve as hydrogen atom donors. 

The base-catalyzed joint reaction of nitroalkenes with thiophenol in the presence of aldehydes gives y-phenylthio-P-nitro alcohols in one pot (Eq. 4.5).8 The joint reaction of nitroalkenes with thiols and a,p-unsaturated nitriles (or esters) has also been achieved. (Eq. 4.6).9 P-Nitro sulfides thus prepared show unique reactivity toward nucleophiles or tin radicals. The nitro... 

The Marshall Unker [23] has been widely used to synthesize compounds that can be cleaved by primary and secondary amines to afford the corresponding amides. Marshall linker was used in the synthesis of three or more diversity-site hbraries because it allowed the addition of one more diversity element at the cleavage step. While the original reported linker [23] involved the oxidation of the Unker before cleavage, the efficient release of the resin-bound compounds using nucleophiles from the unoxidized linker has been reported [16, 24]. Similarly to the acid-labile linkers, the kinetics of the cleavage reaction and time required for this reaction directly affect the synthesis efficiency, purity and yield of the final products. A cleavage study was carried out on seven resin-bound thiophenol esters (34—40) on Marshall Unker with 3 amines (41-43) (Scheme 12.11 and Tab. 12.4). 

The reactivity of seven resin-bound thiophenol esters toward 3,4-dimethoxy-phenethylamine (42) was consistent with the trend seen in n-butylamine cleavage reactions i.e. benzimidazole > alkyl > aromatic. However, the rate constant for the same thiophenol esters with 3,4-dimefhoxyphenethylamine was decreased by two to three fold compared with that with n-butylamine. The rate constant of ben-... 

The reaction of several thiophenols containing suitably positioned functional groups with acetylenic esters give rise to several interesting products. The reaction of pentafluorothiophenol with diethyl acetylenedicarboxylate in the presence of butyl lithium yields 2,3-dicarbethoxy-4,5,6,7-tetrafluorobenzol/>]thiophene (353), formed by... 

OLyfi-Butenolides.1 Reaction of (E)-y-hydroxy-a, (3-unsaturated esters with thiophenol results in cyclization to 3-phenylthiobutyrolactones, which can be converted into 3-phenylthiobutenolides or butenolides. 

Tomioka et al. reported the asymmetric Michael addition of lithium thiolates catalyzed by chiral aminoether 31 (Scheme 8D. 18) [39]. Thus, in the presence of catalytic amounts of 31 (10 mol %) and lithium 2-(trimethylsilyl)thiophenolate 32-Li (8 mol %), thiol 32 (3 equiv.) reacted with a,p-unsaturated esters at -78°C in toluene-hexane solvent to give the Michael adduct with up to 97% ee. In the ahsence of 31, the reaction of thiophenol proceeded in only 0.5% yield at room temperature. A monomeric complex consisting of 31 and lithium is proposed as the key reactive species in this asymmetric reaction. The trimethylsilyl group at the ortho-po-sition of the thiol moiety in 32 contributes to the formation of the stereochemically defined monomeric chelated structure, wherein the lithium cation is coordinated with the three heteroatoms of the tridentate ligand 31. The reactions of acyclic /nmv-a,P-unsaturated esters (R1 = Me, Et, Pr, Bu, Bu, PhCH9 R2 = H) proceeds with high enantioselectivity in... 

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