Thiolate ions acidity

Also as observed for reaction 40, the slopes are less than unity (0.32 for LG = H, 0.40 for LG = OMe, and 0.56 for LG = SMe) due to the sp2 hybridization of the (3-carbon which facilitates overlap with the YY groups at the transition state and reduces the imbalance. However, as the differences in the slopes imply, the degree by which the imbalance is reduced depends on the leaving group and is largest for LG = H and smallest for LG = SMe. This conclusion is corroborated by the Br Ansted-type coefficients a uc and 3 uc for the reactions of thiolate ions with the phenyl-substituted Meldrum s acid derivatives of 71-H and 71-SMe for 71-SMe, a[]uc- 3 uc = 0.34, for 71-H a uc- PnUC = 0-13, implying a smaller imbalance for 71-H. 

Thiols are more acidic than water. Therefore, thiolate ions are easily generated by treating thiols with aqueous sodium hydroxide. 

The stereochemical course of the solvolysis of isomers 136 and 137 was determined by Rappoport and Apeloig (1969). The reaction of both isomers in ethanol-water 4 1 in the presence of thiolate ions, in acetic acid in the presence of acetate and chloride ions and in dimethylforma-mide in the presence of chloride ion affords cis and trans substitution products in the ratio 1 1. The observed racemization indicates that the intermediate precursor of the products is a linear dissociated vinyl cation. 

This particular thiocarbenoid complex and the analogous tungsten derivative are more conveniently synthesized by an initial reaction of [Cr(CO)5 C(CH3)(OCH3) ] or [W(CO)5 C(CH3)(OCH3) ] with benzene-thiolate ion at room temperature followed by acidification with hydrochloric acid. This synthetic route has also been used to prepare a series of pentacarbonyl[(l-phenylthio)ethylidene]tungsten(0) complexes substituted in the 4-position of the phenyl rings.4... 

Thiolate ions are also useful for the demethylation of certain ethers, esters, amines, and quaternary ammonium salts. Aryl methyl ethers can be cleaved by heating with EtS in the dipolar aprotic solvent DMF ROAr + EtS ArO +EtSR. Carboxylic esters and lactones are cleaved (the lactones give co-alkylthio carboxylic acids) with a thiol and AICI3 or AlBrs. Esters and lactones... 

There are no restrictions with regard to the stmcture of the isocyanide (5), as long as it is a C-iso-cyanide. " An acid HX is only suitable as the acid component of the 4CC if it is not irreversibly converted into an a-aminoalkylation product, as happens with the cyanide and the thiolate ions." Furthermore, the acid component HX must yield an a-adduct (41) that is capable of rearranging into a stable product (42). 

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