Sodium Hydroxide → Phenol

Participants

Reaction Steps

Catalyst 1 was prepared as described in preceding application U.S. Ser. No. 10/436,741 (which is incorporated by reference herein), where it is referred to as catalyst C. This phenol was prepared from a theoretical yield of 3.9 mmol of diazotized 2,6-diisopropylaniline (prepared as reported (Helvetica Chimica Acta 1983, 66, 1737)) quenched with a phenolate solution comprised of 2-(9-anthracenyl)-4-methylphenol (0.63 g), water (20 mL), NaOH (20 mmol), pyridine (2 mL), and benzene (4 mL) cooled in an ice bath. The organic layer was collected and depleted of volatiles on a rotary evaporator. The crude ligand, 2-(2′,6′-diisopropylphenylazo)-4-methyl-6-(9-anthracenyl)phenol, was purified by chromatography on silica gel using 10:1 hexanes/diethyl ether as an eluent, followed by crystallized from methanol (slow evaporation at ambient temperature). Yield was approximately 0.30 g (29%). (PPh3)2Ni(Ph)(Br) (560 mg, 0.76 mmol) was added to a solution of potassium 2-(2′,6′-diisopropylphenylazo)-4-methyl-6-(9-anthracenyl)phenoxide (0.56 mmol) in THF (45 mL) (prepared by addition of a slight excess of KH to the purified 2-(2′,6′-diisopropylphenylazo)-4-methyl-6-(9-anthracenyl)phenol) causing a color change to red/brown. After 2 hours, the solvent and residual volatiles were removed and the residue was extracted with pentane (70 mL) and filtered to collect the crude insoluble product, which was dried in vacuo. Residual phosphine was removed by trituration with pentane overnight at −30° C. to give the product as the remaining pentane-insoluble dark red/brown powder. Yield was approximately 310 mg (64%). 1H NMR (C6D6): 1.27 (doublet of doublets; J=7, 18 Hz; 12H); 2.08 (singlet; 3H); 4.26 (septet; J=7 Hz; 2H); 6.29 (multiplet; 3H); 6.58 (triplet; J=8 Hz; 6H); 6.76 (triplet; J=8 Hz; 3H); 6.87-7.19 (multiplet; 16H); 7.63 (doublet; J=8 Hz; 2H); 7.81 (doublet; J=8 Hz; 2H); 7.86 (singlet; 1H); 7.94 (doublet; J=2 Hz; 1H) ppm. The 2-(9-anthracenyl)-4-methylphenol was prepared as follows: A 500 mL round bottom flask was charged with 9-bromoanthracene (20.7 g, 80.5 mmol, 1.1 equivalents) and (PPh3)2NiCl2 (1.33 g, 2.0 mmol, 2.7% catalyst) in approximately 150 mL THF under a nitrogen atmosphere. While stirring at ambient temperature, a freshly prepared magnesium Grignard solution of tetrahydropyran(THP)-protected 2-bromo-cresol (2MgBr-CresolTHP)-(theoretical yield 75.0 mmol, 1 equivalent) in 150 mL THF was added over a 15 minute period with little change in the solution temperature. The reaction was heated at reflux for 5 days, slowly causing a change in color from brown to green. After cooling, the flask was moved to a fume hood and most of the solvent was evaporated via nitrogen flow. The reaction was diluted with 200 mL of hexanes, cooled in an ice bath, and any remaining Grignard or active magnesium compounds were quenched by slow addition of 50 mL water. Recovery of the organic layer and removal of volatiles by evaporation led to a yellow/brown oil that deposited some light yellow powder and crystals of product upon standing. More product was extracted from the oil by adding acetone and collecting the white crystalline material which formed. Removal of acetone in vacuo resulted in 7.8 g of phenol (37% yield). 1H NMR (C6D6, 250 MHz, 22° C.): δ 2.09 ppm, s, 3H; 4.13 ppm, s, 1H; 6.84 ppm, s, 1H; 7.05-7.23 ppm, m, 6H; 7.82 ppm, d, JHH=9.3 Hz, 4H; 8.24 ppm, s, 1H.

Provenance & Evidence