Diisobutylaluminumhydride → (4-Chloro-3-ethoxyphenyl)methanol

Temperature

-78 °C

To a solution of 4-chloro-3-hydroxy-benzoic acid (3.0 g, 17.4 mmol, 1.0 equiv) in DMF (15 mL) was added K2CO3 (4.81 g, 34.8 mmol, 2.0 equiv) and ethyl iodide (4.03 mL, 5.97 g, 38.2 mmol, 2.2 equiv). The reaction mixture was stirred for 6 h at rt, diluted with water (20 mL) and extracted with ethyl acetate (3×50 mL). The organic phases were dried over Na2SO4 and concentrated to afford 3.6 g (91%) of 4-chloro-3-ethoxy-benzoic acid ethyl ester. The crude ester was then dissolved in THF (20 mL) and cooled to −78° C. under Ar. A solution of diisobutylaluminium hydride (95 mL, 95.0 mmol, 6.0 equiv; 1.0 M solution in THF) was slowly added over a time period of 15 min, the cooling bath removed on completion of addition and the reaction allowed to warm up to 0° C. After stirring for 1 h, the reaction was cooled to −78° C. and the excess hydride quenched by cautious addition of a solution of 1 M HCl (10 mL). The mixture was brought to rt, the organic phase separated and the aqueous layer extracted with ethyl acetate (3×100 mL). The combined organic phases were dried over Na2SO4 and concentrated by evaporation under reduced pressure providing 2.94 g (100%) of 4-chloro-3-ethoxy-benzyl alcohol. The crude alcohol (2.94 g, 15.75 mmol, 1.0 equiv) was dissolved in dichloromethane (15 mL) and activated MnO2 (5.48 g, 63.0 mmol, 4.0 equiv) was added. The reaction mixture was stirred for 16 h, after which time the reaction was filtered through Hyflo Super Cel and concentrated. The residue was purified by flash column chromatography on silica eluting with heptane/ethyl acetate (4:1) to yield 1.51 g (52%) of the title compound. 1H NMR (300 MHz, CDCl3): δ1.51 (t, J=7.1 Hz, 3H), 4.19 (q, J=7.1 Hz, 2H), 7.37-7.42 (m, 2H), 7.55 (d, J=9.0 Hz, 1H), 9.94 (s, 1H).

1. customthe cooling bath removed on completion of addition
2. temperatureto warm up to 0° C
3. temperaturethe reaction was cooled to −78° C.
4. customthe excess hydride quenched by cautious addition of a solution of 1 M HCl (10 mL)
5. customwas brought to rt
6. customthe organic phase separated
7. extractionthe aqueous layer extracted with ethyl acetate (3×100 mL)
8. dry with materialThe combined organic phases were dried over Na2SO4
9. concentrationconcentrated by evaporation under reduced pressure

ORD record

ord-6ca194044f254bf4b68faf7b208589c8

Source dataset

uspto-grants-2011_06

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07968568B2