Reaction #1805

Reaction equation

water

1-carbomethoxy-6-methoxy-2-tetralone

resorcinol

phosphorus oxychloride

→

title compound

Yield 70.8%

2-Methoxy-8-hydroxy-11,12-dihydro-5H-benzo[b]naphtho[2,1-d]pyran-5-one

Yield 70.8%

Solvents

toluene

Conditions

Workup

1. 1
   TemperatureAfter cooling to room temperature
2. 2
   Filtrationfiltered
3. 3
   Washrinsing the precipitate with ether
4. 4
   OtherThe filtrate layers were separated
5. 5
   Extractionthe aqueous layer was extracted with ethyl acetate (3×500 mL)
6. 6
   Dryingthe combined organic layers were dried (sodium sulfate)
7. 7
   Concentrationconcentrated
8. 8
   OtherRecrystallization of the residue from methanol

Procedure

To a solution of 1-carbomethoxy-6-methoxy-2-tetralone (see, Colvin, Martin, and Shroot, Chemistry and Industry, 2130 (1966)) (18.0 g, 76.8 mmol) and resorcinol (8.9 g, 80.7 mmol) stirring at ambient temperature in toluene (450 mL) was added phosphorus oxychloride (12.0 g, 7.3 mL, 18.3 mmol) dropwise, and the mixture warmed to 80° C. for 12 h. After cooling to room temperature, the mixture was poured into water (500 mL) and filtered, rinsing the precipitate with ether. The filtrate layers were separated, the aqueous layer was extracted with ethyl acetate (3×500 mL), and the combined organic layers were dried (sodium sulfate) and concentrated. Recrystallization of the residue from methanol provided 16.0 g of the title compound as a yellow solid, mp 244-249 d°C.: 1 H NMR (300 MHz, DMSO-d6) d 10.55 (br s, 1H), 8.24 (d, J=8.6 Hz, 1H), 7.75 (d, J=8.7 Hz, 1H), 6.6-7.0 (m, 4H), 3.76 (s, 3H), 2.8-3.0 (m, 4H); 13C NMR (125 MHz, DMSO-d6) d 170.3, 160.3, 158.3, 158.1, 153.3, 147.7, 137.5, 127.4, 125.8, 122.5, 114.5, 112.6, 112.4, 110.9, 101.4, 54.6, 26.3, 22.7; IR (KBr) 3250, 1676, 1618 cm-1 ; MS (FD+) m/e 294 (M+); Anal. calc'd. for C18H14O4 : C, 73.45; H, 4.80. Found: C, 73.15; H, 4.86.

Source