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Organic Synteses vol 69 - Paquette L.A.

Paquette L.A., Boecman R.K. Organic Synteses vol 69 - John Wiley & Sons, 1990. - 174 p.
ISBN 0-471-54560-0
Download (direct link): organicsynthesesvol691990.pdf
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5. Jansen, R.; Sheldrick, W. S.; Höf la, G. Liebigs Ann. Chem. 1984, 78.
6. Semmelhack, M. F.; Schmid, C. R.; Cortes, D. A.; Chou, C. S. J. Am. Chem. Soc.
1984, 106, 3374.
7. (a) Wakayama, S. J. Chem. Soc. Japan 1951, 72, 275; Chem. Abstr. 1952, 46, 2483f; (b) Bayer, O. In "Methoden der Organischen Chemie" (Houben-Weyl) 4th ed.; Thieme: Stuttgart, 1954; Vol. VII/1, pp. 428-432.
8. Enders, D.; Eichenauer, H. Chem. Ber. 1979, 112, 2933.
9. Badin, E. J.; Pacsu, E. J. Am. Chem. Soc. 1945, 67, 1352.
10. Hoffmann, R. W.; Zeiss, H. J.; Ladner, W.; Tabche, S. Chem. Ber. 1982, 115, 2357.
11. Hoffmann, R. W.; Dresely, S. Angew. Chem., Intern. Ed. Engl. 1986, 25,189.
12. Bobbitt, J. M.; Flores, M. C. L. Heterocycles 1988, 27, 509.
13. Montanari, F.; Penso, M.; Quici, S.; Viganö, P. J. Org. Chem. 1985, 50, 4888.
14. (a) Rozantsev, E. G.; Sholle, V. D. Synthesis 1971, 190; (b) Rozantsev, E. G.; Sholle, V. D. Synthesis 1971, 40I; (c) Keana, J. F. W. Chem. Rev. 1978, 78, 37; (d) Dagonneau, M.; Kagan, E. S.; Mikhailov, V. I.; Rozantsev, E. G.; Sholle, V. D. Synthesis 1984, 895.
15. (a) Montanari, F.; Landini, D.; Rolla, F. Top. Curr. Chem. 1982, 101, 147; (b) Dehmlow, E. V.; Dehmlow, S. S. In "Phase-Transfer Catalysis", 2nd ed.; Ebel, H.
F., Ed.; VCH Pubs: New York, 1983.
218
16 Bomowski, H. In "Methoden der Organischen Chemie” (Houben-Weyl) 4th ed. Thieme: Stuttgart, 1983; Vol. E/3, pp. 265-300.
17 Landini, D.; Montanari, F.; Rolla, F. Synthesis 1979, 134,
Appendix
Chemical Abstracts Nomenclature (Collective Index Number); (Registry Number)
(S)-(+)-2-Methyibutanal: Butyraldehyde, 2-methyl-, (S)-(+)- (8); Butanal, 2-methyl-, (S)-(9); (1730-97-8)
(S)-(-)-2-Methyl-1 -butanol: 1-Butanol, 2-methyl-, (S)-(-)- (8); 1-Butanol, 2-methyl-, (S)-(9); (1565-80-6)
Tetramethylpiperidin-1-oxyl: 1 -Piperidinyloxy, 2,2,6,6-tetramethyl- (9); (2564-83-2)
4-Methoxy-2,2,6,6-tetramethylpiperidin-1-oxyl: 1-Piperidinyloxy, 4-methoxy-2,2,6,6-tetramethyl (11); (95407-69-5)
219
REARRANGEMENT OF 4-ARYL-4-HYDROXY-2,3-DIALKOXYCYCLOBUTENEDIONES TO ANNULATED HYDROQUINONES AND QUINONES: 5,6-DIETHOXYBENZOFURAN-4,7-DIONE
A 500-mL, round-bottomed flask is flame-dried and flushed with nitrogen. The flask is equipped with a magnetic stirring bar and a rubber septum and charged with 4.14 g (60.9 mmol) of furan (Note 1) and 300 mL of dry tetrahydrofuran (Note 2). The solution is stirred and cooled in an ethylene glycol-dry ice bath (-15°C) and 24.17 mL (55.6 mmol) of 2.3 M butyllithium is added slowly by means of a syringe pump (rate =
1.5 mL/min). After complete addition, the solution is stirred an additional 30 min. The ethylene glycol-dry ice bath is replaced with an ice bath and the solution stirred for 1.5 hr at 0°C. The flask is then cooled to -78°C in a dry ice-acetone bath.
A 1000-mL, round-bottomed flask is flame-dried and flushed with nitrogen. The flask is equipped with a magnetic stirring bar and a rubber septum and charged with
O
O
Submitted by S. T. Perri, P. Rice, and H. W. Moore.1 Checked by Ho-Jung Kang and Leo A. Paquette.
1. Procedure
220
9.00 g (52.9 mmol) of diethyl squarate (Note 3) and 450 mL of dry tetrahydrofuran (Note 2). The solution is stirred and cooled in a dry ice-acetone bath at -78°C. The solution of 2-lithiofuran is transferred dropwise via cannula to the flask containing the diethyl squarate which is stirred rapidly. After complete addition (45 min), the solution is stirred for 20 min and quenched by pouring the cold solution into a separatory funnel containing 150 mL of aqueous 10% ammonium chloride and 100 mL of diethyl ether. The separatory funnel is shaken vigorously until phase separation is achieved and all of the ice has melted. The aqueous phase is separated from the organic phase and the aqueous layer is extracted twice with 40-mL portions of diethyl ether. The combined organic layer is washed with 125 mL of brine solution and dried over solid anhydrous potassium carbonate (Note 4) for 5 min with gentle swirling.
The solution is decanted from the potassium carbonate (Note 5) and concentrated on a rotary evaporator (bath temperature = 23-40°C) to approximately 150 mL in a 1000-mL round-bottomed flask. Then 400 mL of dry p-xylene (Note 6) is added and the flask is placed on the rotary evaporator at a bath temperature of 40°C to remove the remaining tetrahydrofuran and diethyl ether. The flask containing the remaining p-xylene solution of the cyclobutenone is fitted with a reflux condenser and heated at reflux for 3 hr under nitrogen. The flask is cooled to ambient temperature and the solvent is removed on a rotary evaporator fitted with a bump trap at a bath temperature of 70°C to give a red oil.
The oil is dissolved in 500 mL of diethyl ether and washed with three 200-mL portions of an ethanolic ferric chloride solution (Note 7). The aqueous layers are separated from the organic phase and extracted with four 100-mL portions of diethyl ether. The combined organic layer is washed with saturated sodium bicarbonate solution (Note 8) until the aqueous wash is no longer acidic. The resulting neutralized aqueous extracts are combined and extracted with three 30-mL portions of diethyl ether. The organic extracts are combined, washed with 150 mL of brine solution and
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