Methyl 3-oxovalerate → Methyl 3-hydroxypentanoate

Beteiligte Stoffe

Reaktionsschritte

A solution of methyl-3-oxo-pentanoate (31) (20 g) noyori hydrogenation with RuCl2 [(S)-BINAP] (60 mg), in methanol was added. The flask was charged with hydrogen gas (5 atm) at 100° C. The resulting suspension was vigorously stirred for 48 hours. The reaction mixture was diluted with methanol and the combined organic layers were filtered through a Celite pad. The combined organic phases were evaporated in a rotary evaporator to yield the product (S) isomer of methyl-3-hydroxy-pentanoate (32). The methyl-3-hydroxy-pentanoate (secondary alcohol-32) was protected with TBDMSCl in the presence of imidazole in dichloro methane. The reaction mixture was stirred for 24 hours at room temperature. This reaction was quenched with aqueous saturated sodium bicarbonate and extracted with dichloro methane. The combined organic phases were dried over Na2SO4 and the combined organic phases were evaporated in a rotary evaporator to yield the TBS protected product (33). A stirred solution of ester was reduced with di-isobutyl aluminum hydride in dichloro methane at −78° C. for 5 hours. This reaction mixture was quenched with saturated aqueous sodium potassium tartarate. The combined organic and aqueous layers were filtered and organic layer was separated by separating funnel. The aqueous layer was extracted with dichloro methane. The combined organic phases were dried over Na2SO4 and the combined organic phases were evaporated in a rotary evaporator to yield the product primary alcohol (34) as a pale yellow liquid. The primary alcohol was protected with methane sulfonyl chloride in the presence of TEA in dichloromethane. The reaction mixture was stirred for 4 hours at 0° C. This reaction was quenched with aqueous saturated sodium bicarbonate and extracted with dichloro methane. The combined organic phases were dried over Na2SO4 and the combined organic phases were evaporated in a rotary evaporator to yield the methane sulfonyl protected product (35). The methane sulfonyl protected primary alcohol was stirred at 70° C. with NaN3 in DMF for 16 hours. A stirred solution of TBS protected secondary alcohol. This reaction was quenched with pre cooled ice water and extracted with diethyl ether. The combined organic phases were dried over Na2SO4. The combined organic phases were evaporated in a rotary evaporator to yield the azido product as a colorless liquid (36). This was deprotected with TBAF in tetrahydrofuran at room temperature. This reaction was quenched with saturated ammonium chloride solution and extracted with diethyl ether; the combined organic phases were dried over Na2SO4 and evaporated on rotary evaporator to yield the product 1-azido-3-pentanol (36A) as a colorless liquid.

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