Dicyclohexyl-18-crown-6-Potassium cyanide

Cyanosilylation of ketones (4,542-543 5,720). In a total synthesis of natural camptothecin (9), Corey et al used this f-butyldimethylsilyl derivative rather than trimethylsilyl cyanide (5, 720-722) to effect cyanosilylation of a ketone (1). Hydrolysis of the resulting cyano silyl ether to the required amide was not accompanied by desilylation with reversal of cyanohydrin formation. By use of carefully controlled conditions and with dicyclohexyl-18-crown-6-potassium cyanide as catalyst, they were able to convert (1) into the a-hydroxy... 

A crown ether can facilitate substitution between an unactivated aryl chloride and potassium methoxide. Thus, heating a solution of the dicyclohexyl-18-crown-6 complex of potassium methoxide in o-dichlorobenzene at 90° gives rise to 40—50% of o-chloroanisole, Eq. (3). No reaction is observed in the absence of the ether.25 This approach is not always successful, however. The same ether failed to induce a reaction between potassium cyanide and o-dichlorobenzene in acetonitrile.24 ... 

Hydroxy linkers bearing an electron-withdrawing group such as an a-carbonyl (oxyacyl resins, phenacyl type-linkers or glycolic acid derivatives) are also suitable for the nucleophilic release of ester bound compounds. The glycolamidic ester linker 10 has been successfully used to synthesize peptides by the Fmoc/tBu strategy. It is compatible with the repetitive piperidine treatment but peptides can be cleaved with dilute NaOH solutions, ammonia or alkoxides [9], Esters bound to oxyacyl resins 8 have been reported to be cleavable by thiolysis, saponification, ammonia, hydrazine and potassium cyanide (complexed with dicyclohexyl-18-crown-6) [10, 11],... 

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