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8.4.3.1.1 Variation 1: Macrocyclic Lactones

DOI: 10.1055/sos-SD-008-01308

Kellogg, R. M.Science of Synthesis, (200681498.

On treatment with cesium carbonate (102M in DMF), the (racemic) iodo-substituted carboxylic acid 1 affords lactone 2 in 76% yield and lactone dimer 3 in 7% yield (Scheme 1).[‌2‌] In the synthesis of an analogous 16-membered-ring lactone, the following different alkali metal carbonates have been compared (the yield of the monomeric lactone is given in parentheses): cesium carbonate (80%), rubidium carbonate (68%), potassium carbonate (67%), sodium carbonate (54%), and lithium carbonate (0%, no conversion). Conversions were highest and most rapid when cesium carbonate was used.

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