Solid-liquid phase-transfer catalysis. lactone

Cyclization of the methanesulfonate of 12-hydioxydodecanoic acid in toluene with aqueous sodium bicarbonate and a 1% cross-linked, DF 0.04, (polystyrylmethyl)tri-n-butylphosphonium ion phase transfer catalyst gave 66% yield (1321. However, the concentration of substrate in the final reaction mixture was 2.3 mM, no higher than in most high dilution experiments. A more promising method is solid-liquid phase transfer catalysis. A 0.1M suspension of the potassium salt of 12-bromododecanoic acid in toluene containing 2.5 Mm tetra-n-butylammonium bromide was heated at 90 °C to give 95% of the 13-membered lactone (Equation 32) (1331. Effective concen-... 

Fig. 17 Lactone synthesis by solid-liquid phase-transfer catalysis.

Oxepins.- Several macrocyclic lactones have been made by a simple solid-liquid high dilution phase-transfer-catalysis process (Scheme 16).71... 

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