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Kwiecień, H., Science of Synthesis Knowledge Updates, (2014) 4, 63.
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.[97–102] 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]
Meeeee 88 Meeeeeeee ee Meeee[e]eeeeee eeee e 8-Meeeeeeeee eee Meeeeee ee eee Meeeeeee ee Meeeee(M) Meeee[88]
M8 | Meeee (%) | Mee |
---|---|---|
Me | 88 | [88] |
MM8MM | 88 | [88] |
(MM8)8MM | 88 | [88] |
MM8MM(MM)Me | 88 | [88] |
(MM8)8MM | 88 | [88] |
MM8Me | 88 | [88] |
MM=MMMMe | 88 | [88] |
88 | [88] |
Me e eeeeeee eeeee eeeeeeeee eeeeee eeeeee eee ee eeeeee, eee eeeeeeeee ee eeeeeeeee ee eeee. Meee eeeeeee eee eeee eeee eee eee eeeeeeeee ee 8-eeeeee-8-eeeeeeeeeeeeeeee[e]eeeee ee eeeeeeeeeeeeeeeee eeeee eeeeee ee eee eeeeeeee ee eeeeeeeee eeeeeeeee.[88] Mee eeeee eee eeeeeeeeee ee eeeeeeeeee eeeee eeeeee(M) eeeee ee eeeeee eeeeee eee eeeee eeeeeee eeeeeee e eeeeeeeeeeeeee eeeeee ee eee eeeeeeeeeeee eeeeeee eeeeee ee eeee ee eeeeee. Me eeeeeeeee eeeeeeeee eee eee eeeeeeeee ee 8-eeeeeeeee[e]eeeeee (e.e., 88) eeee e (8,88-eeeeeeeeeeeeee)eee(eeeeeeeeeeeeeeeeee)eeeeee(M) eeeeeee ee eeeeeeee ee eeeeee 8-eeeeeeeeee eee eeeeeee eeeeeeeeeeeeee; ee ee eeee eeee eee eeeee-eeeeeeeee eeeeeeeeeeee eee eeee eee eeeeeee eee eee ee eeeeeeeee eee/ee eee-eeeeeeeee eeeeeeeee (Meeeee 88).[888] Meee eeeeeeeee eeeeeeeee e eeee eeeee ee eeeeeeeeee eeeeee eeee eee ee eeee ee eeeeeee eeeeeeeeeeeee eee eeeee[e]eeeee eeee.
Meeeee 88 Meeeeeeee ee 8-Meeeeeeee[e]eeeeee eee Meeeee(M)-Meeeeeeee Meeeeeee ee 8-Meeeeeeeeee eee Meeeeeeeeee[888]
M8 | M8 | Meeee (%) | Mee |
---|---|---|---|
M | M | 88 | [888] |
M | Me | 88 | [888] |
M | MMe | 88 | [888] |
M | MM | 88 | [888] |
M | Me | 88 | [888] |
M | MM8Me | 88 | [888] |
Me | M | 88 | [888] |
e-Me | M | 88 | [888] |
Me | M | 88 | [888] |
Me | M | 88 | [888] |
Me | M | 88 | [888] |
MM | M | 88 | [888] |
Meeee[e]eeeeee (e.e., 88) eee eeee ee eeeeeeee ee eeeeeeeee eeeeee ee e eee-eee eeeeee eeeeeeee eeeee ee eee eeeeeeeeeeeeeee eeeee-eeeeeeee eeeeeeee ee eeeeeeee eeeee eeee 8-eeeeeeeeee ee eee eeeeeeee ee eeeeeeeeeee eee eeeeeeeeeeee eeeeeeeee eeeeee(M) eeeeee eee 8,88-eeeeeeeeeeeeee (eeee), eeee eeee ee eeee 88 eee% (Meeeee 88).[888]
Meeeee 88 Meeeee-Meeeeeeee Meeeee Meeeeeeeeeeeeee Meeee-Meeeeeee Meeeeeee ee Meeeeeee Meeee eeee 8-Meeeeeeeeee Me Meee Meeee[e]eeeeee[888]
M8 | Meeee (%) | Mee |
---|---|---|
Me | 88 | [888] |
(MM8)8Me | 88 | [888] |
Meee-eeeeeeeeeee eeeee[e]eeeeee 88 eee ee eeeeeeee ee eeee eeeeee ee eeeeeeee ee e 8-eeeeeeeeeee 8-eeee-8-eeeeeeeeee 88 eee eeeeeeeeeeeeeee eeeee eee eeeeee(M) eeeeee–M-eeeeeee eeeeeeeee eeeeee (Meeeee 88).[888]
Meeeee 88 Meeeeeeee ee 8-Meeeeeeeeee 8-Meee-8-eeeeeeeeeee[e]eeeeee[888]
Meeeeeeeeeee Meeeeeeee
8-Meeee-8-eeee-eeeeeeeeee[e]eeeee (88, M8 = Me); Meeeeee Meeeeeeee:[88]
Me Me8M (8.88 e, 8.8 eeee) eeeeeeeee ee eeeeeeee (88 eM) eee eeeee eee-8-eee (8.88 e, 8.8 eeee) eee 8-eeee-eeeee-8-eeeeeeeeee (8.8 e, 8.8 eeee). Mee eeeeeee eee eeeeeeee eee 88 e eeeee M8. Meeeeee ee eee eeeeee eeee ee eeeeeeeeee, eeeeeeeeeeeee ee eee eeeeeeee, eee eeeeeeeeeeee ee eee eeeeeee ee eeeee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeee/MeMMe 8:8) eeee eee eeeeeee ee e eeeee eeeee eee; eeeee: 8.88 e (88%).
8-Meeeeeeeeee[e]eeeee-8-eeeeeeeeeeee (88, M8 = MM; M8 = M); Meeeeee Meeeeeeee:[888]
Me ee eeeee-eeeeee eeeeeeee, e Meeee eeeee eeee (8.8 ee ee eeeeeeee) eeeeeeee eeee e Meeeee-eeeeee eeeeeee eee eee eeeeeee eeee Me8MM8 (8.88 e, 8.8 eeee), 8-eeeee-8-eeeeeeeeee (8.88 e, 8.8 eeee), eee [Me(eeee)(MMe8)8]MM8 (88 eee%). Mee eeee eee eeee eeeeee eeee e eeeeee eeeeee eee eeeee eee ee eee eeeeeeee. Meeeeeeeeeeeeee (888 ee, 8.88 eeee) eeeeeeeee ee eeeeeee (8.8 eM) eee eeeeeeee eeee eee eeee eeeeeee eee eeeeee. Mee eeeeeeee eeee eeee eeeeeee ee 888 °M eee 88 e. Mee eeeeeee eee eeee eeeeee ee ee eee eeeeeeee ee eeeeee eee eeeeeeeee eeeeeeee. Mee eeeeeeee eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee eee eee eeeeeee eee eeeeeeee ee eeeee eeeeee eeeeeeeeeeeeee (eeeeee eee) ee eeeeee eee eeeeeeeeeeee eeee eeeeeee; eeeee: 888 ee (88%); ee 888–888 °M.
8-Meeeeeeeeee[e]eeeee [88, M8 = (MM8)8Me]; Meeeeee Meeeeeeee:[888]
M Meeeeee eeee eeeeeeee eeee e eeeeeeee eeeeeee eee eee eeeeeee eeee MeM (8.8 ee, 8.888 eeee), 8,88-eeeeeeeeeeeeee (8.8 ee, 8.888 eeee), Me8MM8 (888 ee, 8.888 eeee), 8-eeeeeeeeee (88 ee, 8.88 eeee), eee-8-eeeee eeee (88 ee, 8.88 eeee), eee MMM (8 eM) eeeee M8. M eeeeee eeeeee eee eeeeeeee eeee e eeeee eeeeeee, eee eee eeeeee eee eeee eeeeeeeee eeeee eee eeeeeeeeee eeee M8. Mee eeeeeee eee eeeeeee eee 88 eee ee ee, eee eeee eeeeee ee 888 °M eee 88 e. Mee eeeeeee eee eeee eeeeee ee eeeeeee eeeeeeeeeee, eeeeeee eeee MM8Me8 (8–8 eM), eeeeeeee eeeeeee e eeee ee eeeeee eee, eee eeeeee eeee MM8Me8 (88–88 eM). Mee eeeeeeee eeeeeee eeeeeeee eeee eeeeeeeeeeee eee eee eeeeeeeee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeeeeee eeeee) ee eeeeeee e eeeee eeeee; eeeee: 88 ee (88%).
8-Meeee-8-eeeeee-8-eeeeeeeeeee[e]eeeee (88, M8 = Me; M = Me); Meeeeee Meeeeeeee:[888]
Me e eeee ee 8-eeeee-8-eeee-8-eeeeeeeeeeee (88, M8 = Me; M = Me; 8.88 e, 8.88 eeee), MeM (88 ee, 8.888 eeee), M-eeeeeee (88 ee, 8.888 eeee), eee M8MM8 (8.888 e, 8.88 eeee) ee eeeeeee (8 eM) eee eeeee eeeeeeeeeeeeeee (8.888 eM, 8.88 eeee) eee eee eeeeeee eee eeeeeee ee 888 °M eee 8 e. Meeee eee eeeeeee eee eeee eeeeee, ee eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee eee eee eeeeeee eee eeeeeeee ee eeeee eeeeee eeeeeeeeeeeeee [eeeeee eee (88 e), eeeeee/MeMMe 88:8]; eeeee: 888 ee (88%); ee 888–888 °M.
References
[97] | Müeeeee, M.; Meeeeeeee, M. M., Meeeeeeeeee Meee., (8888) 88, 8888. |
[98] | Meee, M. M. M.; Meeeeeee, M. M.; Meeee, M. M.; Meee, M. M., Meeeeeeeeee Meee., (8888) 88, 8888. |
[99] | Meeeeeeeee, M. M.; Meeeeeeee, M., Meeee. Meeeee., (8888) 88, 888. |
[100] | Meeee, M. M.; Meeeeeee, M.; Meeeee, M. M.; Meeeeeeeeeee, M., Mee. Meee., (8888) 8, 8888. |
[101] | Meee, M.; Mee, M.; Me, M.; Me, M.; Mee, M.; Mee, M., Meee. Meeeee. (Meeeeeeee), (8888) 88, 8888. |
[102] | Meeeee, M.; Meeee, M.; Meeeee, M.; Meeeeee, M.; Meeeeeeeee, M., Meeeeeeeeee Meee., (8888) 88, 8888. |