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10.1.1.1.1.1.1.2 2-Halophenols and Alkynes with a Copper Catalyst

DOI: 10.1055/sos-SD-110-00529

Kwiecień, H.Science of Synthesis Knowledge Updates, (2014463.

The usefulness of benzo[b]furan synthesis starting from a copper(I) acetylide is dimin­ished by the need to prepare and isolate the starting compound. Moreover, some copper acet­ylides are reputed to be shock sensitive and explosive. Furthermore, many of the functionalized copper(I) acetylides (e.g., hydroxy, ester, nitrile) are soluble in or reactive toward the mixtures used in their preparation. However, there are a variety of one-step strategies to substituted benzo[b]furans that consist of the reaction of a 2-halophenol with an acetylene in the presence of copper(I) oxide, copper powder, copper(I) iodide, or a copper complex and an inorganic salt, such as cesium or potassium carbonate, or tripotassium phosphate.[‌97‌‌102‌] All the methods are free from the above-mentioned disadvantages. The procedure using copper(I) oxide, especially, can accommodate the presence of a variety of reactive functional groups such as hydroxy, ester, lactone, enol ether, and acetal, and yields of benzo[b]furans (e.g., 44) obtained via this procedure are in the 60–82% range for a variety of alkynes (Scheme 22).[‌97‌,‌98‌]

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References