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10.1.1.1.2.2.1.2 Using a Copper Catalyst

DOI: 10.1055/sos-SD-110-00529

Kwiecień, H.Science of Synthesis Knowledge Updates, (20144162.

A variety of 2-aryl- and 2,3-disubstituted benzo[b]furans 278 can be prepared efficiently using copper(I) iodide as the catalyst in the ring closure of (2-haloaryl)alkyl ketones 277 (Scheme 131).[‌249‌] This reaction proceeds smoothly when either potassium or cesium carbonate or potassium phosphate are used as bases. Potassium phosphate is the most effective, giving 2-arylbenzo[b]furans 278 in over 90% yields. Under the same conditions, (2-bromoaryl)alkyl ketones 277 (X = Br) as well as (2-iodoaryl)alkyl ketones 277 (X = I) are readily cyclized to give benzo[b]furans in good yields. Aromatic ketones 277 (R2 = aryl) cyclize to the corresponding benzo[b]furans more readily than alkyl ketones 277 (R2 = alkyl). Presumably, this is due to the aromatic group facilitating the enolization.[‌249‌]

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