Thiolate anions

Nu = malonate anion, amines, thiolate anion, enamines, cuprates (usually requires double activation of cyclopropane)... 

The higher reactivity of 2-halogenothiazoles with respect to halogenopyridines can be related to the different aromaticity of the two systems, less for thiazole than for pyridine, for example, the relatively stronger fixation of the tt bond in the thiazole than in the case of pyridine. As the data reported in Table V-1 (footnote a) indicates, the free thiophenol is more reactive than the thiolate anion toward the 2-halogenothiazoles. This fact should be considered when one prepares the thiazolyl sulfides. 

Thiirane 1-oxide undergoes acid-catalyzed ring opening by ethanethiol to give ethyl 2-ethylthioethyl disulfide. Treatment of thiirane 1,1-dioxide with thiolate anions, sodium sulfide or thiourea gives /3-mercaptosulfinic acid derivatives (75S55). Thiiranium ions are attacked at carbon by most sulfur nucleophiles (79ACR282), but see Section 5.06.3.4.3 for exceptions. 

Schemes 110-113 outline the most common general methods for accomplishing the synthesis of thiiranes by formation of a C—S bond (75RCR138,66CRV297, 64HC(19-1)576). The methods in Schemes 111-113 are variations of Scheme 110 they differ in the details of the generation of the thiolate anion which effects the ring closure by a displacement reaction. The methods of converting oxiranes to thiiranes, to be discussed separately (Section 5.06.4.3), involve a displacement like thafof Scheme 110 as the final step.

Replacement of bromine in ethyl bromofluoroacetate by thiolate anions occurs easily [44] (equation 40)... 

Alkylation of thiolate anions by bromochlorodifluoromethane generally follows this mechanism [55, 57] However, depending on the nature of the nucleophile and reaction condibons, disubstimtion can arise by a SET process [57] (equation 49)... 

TYie, perfluoroalkylations of thiolate anions are interpreted by an mechanism [55, 63, 64] (equation 57). 

Treatment of a thiol with a base, such as NaH, gives the corresponding thiolate ion (RS-), which undergoes reaction with a primary or secondary alkyl halide to give a sulfide. The reaction occurs by an Sn2 mechanism, analogous to the Williamson synthesis of ethers (Section 18.2). Thiolate anions are among... 

Thiols, the sulfur analogs of alcohols, are usually prepared by Sjv 2 reaction of an alkyl halide with thiourea. Mild oxidation of a thiol yields a disulfide, and mild reduction of a disulfide gives back the thiol. Sulfides, the sulfur analogs of ethers, are prepared by an Sk2 reaction between a thiolate anion and a primary or secondary alkyl halide. Sulfides are much more nucleophilic than ethers and can be oxidized to sulfoxides and to sulfones. Sulfides can also be alkylated by reaction with a primary alkyl halide to yield sulfonium ions. 

From Acylated Glycosyl Halides by Reaction with Thiolate Anion. 181... 

In this classic41 and general method, an acylated glycosyl halide reacts with a thiolate anion to produce a 1-thioglycoside, usually with 1,2-trans configuration. With alkyl thiolates, re-acylation is normally required following this treatment. 

Ono and Kamimura have found a very simple method for the stereo-control of the Michael addition of thiols, selenols, or alcohols. The Michael addition of thiolate anions to nitroalkenes followed by protonation at -78 °C gives anti-(J-nitro sulfides (Eq. 4.8).11 This procedure can be extended to the preparation of a/jti-(3-nitro selenides (Eq. 4.9)12 and a/jti-(3-nitro ethers (Eq. 4.10).13 The addition products of benzyl alcohol are converted into P-amino alcohols with the retention of the configuration, which is a useful method for anri-P-amino alcohols. This is an alternative method of stereoselective nitro-aldol reactions (Section 3.3). The anti selectivity of these reactions is explained on the basis of stereoselective protonation to nitronate anion intermediates. The high stereoselectivity requires heteroatom substituents on the P-position of the nitro group. The computational calculation exhibits that the heteroatom covers one site of the plane of the nitronate anion.14... 

Potential energy sections were calculated for R = CH3 and R = Ph, and X = F, Cl, Br, I, in the geometrical scheme shown in Fig. 16 a. The relative ease of approach of the thiolate anion in the xy plane was discussed in terms of the relative energies and positions of potential energy minima, possibly corresponding to reaction intermediates. Fig. 16b and 16c show, for a-attack, the positions and relative energies of these minima. No such minima were found for /3-attack, while hints for a possible linear RCC—X. .. SH intermediate were found for bromo- and iodophenylacetylene only. The conclusions drawn were a) a-attack is favoured over /3-attack, and b) the order of reactivity with respect to the... 

Bis(benzotriazol-lyl)methanethione 974 is easily prepared from thiophosgene and l-(trimethylsilyl)benzotriazole <1978JOC337>. In reactions with thiols and triethylamine, thiones 974 are converted to derivatives 973 in modest yields the main side products result from nucleophilic attacks of the thiolate anions on the thione sulfur atom to produce disulfides <2005JOC7866>. In reactions with amines, compounds 974 are smoothly converted to l-(thiocarbamoyl)benzotriazoles 975 <2004JOC2976>. Substitution of one of the benzotriazolyl groups in 974 by phenolate anions yields l-(aryloxythioacyl)benzotriazoles 978 (Scheme 161) <2005JOC7866>. 

Roberts, D. D., Lewis, S. D Ballou, D. P., Olson, S. T and Shafer, J. A. (1986) Reactivity of small thiolate anions and cysteine-25 in papain toward methyl methanethiosulfonate. Biochemistry 25, 5595-5601. 

Other postulated routes (Jourd heuil et al., 2003) to RSNO formation include the reaction between NO and 02 to yield N02 via a second-order reaction. NO and thiolate anion, RS, react giving rise to thiyl radical, (RS ) [e]. RS then reacts with NO to yield RSNO [f]. The reaction between RS and RS- can also be the source of non-enzymatic generation of superoxide anion (02 ) [g], [h]. 02 reacts with NO to produce peroxynitrite (ONOO ) [i] (Szabo, 2003). Thiols react with ONOOH to form RSNOs [k] (van der Vliet et al.,1998). 

This suggests that the attack of the thiolate anion, at least with this product, occurs principally on the 3-position of the furoxan ring. An alternative mechanism to that discussed above was proposed to explain NO-donation by this product. It implies the preliminary cleavage of the 1-2 bond of the furoxan ring, rather than of the 2-3 bond as suggested by Feelisch, to give a tertiary nitroso intermediate. Reasonable mechanisms may be put forward to explain the production of different NO-redox forms from this intermediate [20] (Scheme 6.9). Interestingly, some furoxans, such as 31 and related compounds, produce NO, detected as nitrite, spontaneously without the assistance of thiols [21]. 

The attack by the thiolate anion on the N-oxide oxygen of 62 produces the intermediate sulfenic acid derivative 65, which, in the presence of thiols, further reacts with the thiolate anion, to give the oxime 66, which has been isolated among the reaction products. By contrast, spontaneous loss of the halide anion from 65 affords the ni-troso intermediate 67 that, by losing NO and the thiyl radical directly, or through 68, produces the a-nitrosoolefm 69. By a Michael type reaction with water this last product immediately yields the final oxime 70, which has been isolated among the reaction products. 

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