Nickel tert-butoxide

The reaction of 571 with isopentyl nitrite in the presence of potassium tert-butoxide gave 5-oximinotriazinobenzodiazepine 576, which was hydrogenated over Raney nickel to give aminotriazinobenzodiazepine 577 (88EUP272868). 

The required 1-oxa-l,3-diene precursor was synthesized according to the synthesis design (Scheme 8). Cycloadditon with enol ether furnished exclusively the endo-isomer. Raney nickel treatment in refluxing ethanol yielded in one step the desired tetrahydropyran derivative in a favorable 6 1 cis/trans ratio. Transformation into the lactone and ring closure with potassium tert.-butoxide afforded (+)-ramulosin. 

The same group reported an extension of the direct alkylation of (benz)oxazoles with various alkyl bromides and chlorides by using the stronger base lithium tert-butoxide (Scheme 19.23) [38]. 5-Aryloxazoles containing electronically diverse substituents such as CFj and OMe were also alkylated successfully. Various linear alkyl chains were introduced, such as phenylpropyl, citronellyl, or octyl, affording interesting lipophilic molecules. The optimized reaction conditions failed to apply to benzothiazoles, and the authors had to turn their attention to nickel catalysis to achieve the corresponding alkylation (Section 19.2.3). Experiments were run to understand the reaction mechanism that presumably involves Sj 2-type oxidative addition of the alkyl halide to palladium(O) followed by transmetallation by the in situ-lithiated (benz)oxazole (Scheme 19.24). 

The alkoxide derivatives of divalent chromium (as well as manganese, cobalt, and nickel) are all insoluble non-volatile products and their insolubility may be attributed to their polymeric nature. Chromium trialkoxides are also insoluble, except the tri-tert-butoxide which is a soluble dimeric compound. " Chromium tri-tert-butoxide when heated in vacuo yielded volatile Cr(OBu )4 and nonvolatile [Cr(OBu )2] ... 

In a comparative study of the alcoholysis reactions of titanium alkoxides, the facility of replacement reactions appears to follow the trend OBu > OPr > OEt > OMe. This type of comparative trend appears to be particularly marked in the alkoxides of some later 3d transition metals. For example, primary alkoxides of d nickel(n) do not appear to undergo alcoholysis reactions with secondary or tertiary and other primary alcohols, whereas the reactions of nickel(n) tert-butoxide with primary alcohols are highly facile. 

The reaction of l-iodo-5-decyne, nickel carbonyl, and potassium tert-butoxide leads to a mixture of three ester products (CLXXXIII)-(CLXXXV) (Crandall and Michaely, 1973). 

However, a mixture of nickel carbonyl and potassium /er/-butoxide in tert-butyl alcohol is a very powerful agent and can carboxylate even alkyl iodides. The carboxylation of cis- and /ran -jS-bromostyrene proceeds in a highly stereospecific manner with retention of double-bond configuration. The... 

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