4-Hydroxybenzaldehyde → Bromide ion

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The procedure of Example 1, Part A was used to prepare 2-(5-methyl-2-phenyl-4-oxazolyl)ethanol from ethyl 5-methyl-2-phenyl-4-oxazoleacetate. 4-[2-(5-methyl-2-phenyl-4-oxazolyl)ethoxy]benzaldehyde was prepared following the procedures of Preparation 2, herein, using para-hydroxybenzaldehyde instead of 3-hydroxybenzaldehyde and 2-(5-methyl-2-phenyl-4-oxazolyl)ethanol instead of 2-(2-phenyl-4-oxazolyl)ethanol. The aldehyde was reduced to 4-[2-(5-methyl-2-phenyl-4-oxazolyl)ethoxy]benzyl alcohol following the procedures of Example 22, Part A. A solution of 3 gm (0.01M) of 4-[2-(5-methyl-2-phenyl-4-oxazlyl)ethoxy]benzyl alcohol in 30 mL CH2Cl2 was treated with 1 mL of PBr3 and kept at ambient temperature for 2 h. The solution was treated cautiously with 2 mL of MeOH and evaporated in vacuo. The residue was dissolved in EtOAc, the solution washed with cold H2O, then with 20% NaHCO3, then with H2O, then with brine, and finally dried over MgSO4. Removal of solvent in vacuo afforded the solid bromide (2 g, 6 mM). The solid bromide was dissolved in 20 mL THF and and the solution was added drop-wise to a solution prepared by the reaction of 0.42 g of 60% NaH/oil dispersion (10 mM NaH), 1.6 gm (5.2 mM) of N-CBZ Diethylaminomalonate hydrochloride and 30 mL of EtOH. The subsequent reaction was allowed to proceed at ambient temperature for 12 h, during which time a precipitate had formed. TLC demonstrated the consumption of starting materials. The mixture was treated with 20 mL H2O and NaOH (1.1 g), stirred, and heated to reflux for 1 h. The cooled mixture was acidified to pH 2, diluted with H2O and extracted with EtOAc. The combined EtOAc extracts were washed with H2O, thwn with brine, and finally dried with MgSO4. Removal of solvent afforded a yellow taffy which crystallized from EtOAc/Hexane to provide the product as a white powder (0.78 g, 16% overall).

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