Crown ether mainly used to complex potassium ions. For a comprehensive study of solvent effects on complexation with K ions in a wide range of solvents, see: J. Org. Chem., 61, 5221 (1996). Promotes methylation reactions with Dimethyl- carbonate: Synthesis, 382 (1986). N-Alkylation of Glutarimide, and Succinimide: Bull. Soc. Chim. Fr., 227 (1992). Enables KH to metallate aryl-substituted methanes directly: J. Am. Chem. Soc., 99, 4457 (1977). In the presence of KOH in DME, various arylmethanes, benzyl alcohols and aldehydes are oxidized to carboxylic acids by molecular oxygen: Tetrahedron Lett., 25, 4989 (1984). Has been used with KF to enhance the reactivity of F- as a base or a nucleophile, e.g. to promote Michael additions in aprotic solvents: J. Chem. Soc., Chem. Commun., 237 (1977), the condensation of nitromethane with aldehydes: Tetrahedron Lett., 3219 (1978), and the transesterification of diaryl to dialkyl phosphonates: Synthesis, 409, 412 (1982). Crown ether catalysis can be used in the reaction of KCN with alkyl halides to give nitriles: Tetrahedron Lett., 71 (1975), and for the preparation of acyl cyanides from acid chlorides: Tetrahedron Lett., 21, 2959 (1980). The 1:1 complex between 18-crown-6 and KCN has been used catalytically in the cyanosilylation of aldehydes, ketones and quinones with TMSCN; for examples, see: Org. Synth. Coll., 7, 517 (1990).
