Salt substitute, sodium introduction

Some strategies used for the preparation of support-bound thiols are listed in Table 8.1. Oxidative thiolation of lithiated polystyrene has been used to prepare polymeric thiophenol (Entry 1, Table 8.1). Polystyrene functionalized with 2-mercaptoethyl groups has been prepared by radical addition of thioacetic acid to cross-linked vinyl-polystyrene followed by hydrolysis of the intermediate thiol ester (Entry 2, Table 8.1). A more controllable introduction of thiol groups, suitable also for the selective transformation of support-bound substrates, is based on nucleophilic substitution with thiourea or potassium thioacetate. The resulting isothiouronium salts and thiol acetates can be saponified, preferably under reductive conditions, to yield thiols (Table 8.1). Thiol acetates have been saponified on insoluble supports with mercaptoethanol [1], propylamine [2], lithium aluminum hydride [3], sodium or lithium borohydride, alcoholates, or hydrochloric acid (Table 8.1). 

Mild N-arylations of indoles can be achieved in good yields by nucleophilic substitution reactions of the sodium salt of indole on various haloarenetricarbonylchromium complexes. Thus, o-fluoroanisole-Cr(CO)3 33a reacts with the indole N anion within 0.75 h at 0 °C to give complex 3m (Nu = indolyl) in 83 % yield. The chloro derivatives require longer reaction times and higher temperatures (Scheme 18) [37]. The authors were able to extend this procedure to the introduction of two indole rings on the same aromatic nucleus. 

Stirring of neat alkyl chloride with a solution of sodium cyanide in water does not result in the substitution reaction, because the reaction partners alkyl halide and cyanide anion, are located in mutually immiscible phases and cannot enter into an intimate contact. Addition of a small quantity of a lipophilic TAA salt to such a system promotes the reaction via continuous introduction of cyanide anions into the organic phase in the form of Q" CN . The simplest mechanistic picture of this catalytic action is presented in Eq. (85) ... 

---