Yield:-

Reaction Conditions:

with polyphosphoric acid at 85; for 8 h;

Steps:

General procedure of synthesis of benzoheterocycles 4a-4e, 5a, 5b, 6a, and 6b.

General procedure: To a mixture of 1.2 mmol (200 mg) of ethyl-2-diazo-3-oxobutanoate (3) and 1.1 mmol of phenol (1a-1f, 2) in toluene, 2.4 ×10-5 mmol (8 mg) of the Cu(OTf)2 catalyst was added. The reaction mixture was heated to 110°C for 2 h. Then, the reaction mixture was cooled to room temperature, and the solvent (toluene) was removed under reduced pressure. Polyphosphoric acid (300 mg) was preheated to 85°C and added to the crude reaction mixture. The viscous mixture was stirred at 85°C for 8 h. After the reaction completion, the reaction mixture was cooled to 0°C; then, water (20 mL) was added, and the mixture was extracted with benzene (30 mL × 3). The organic layer was dried by MgSO4, which was filtered off, and the solvent (benzene) was removed under reduced pressure. The residue was chromatographed on silica gel (elution with petroleum ether : ethyl acetate = 100 : 1).

References:

Sakhabutdinova;Raskil’dina;Zlotskii;Sultanova [Doklady Chemistry,2018,vol. 482,# 2,p. 233 - 236][Dokl. Akad. Nauk,2018,vol. 482,# 5]