1,8-Diazabicyclo(5.4.0)undec-7-ene → HCID 11035521, compound

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Reaction Steps

To a solution of 50.3 g (0.136 mole) of product of example 14 in 200 ml of DMF is added 21.3 g (0.563 mole) of sodium borohydride. The reaction mixture becomes exothermic and the temperature of the reaction mixture rises to 65° C. and subsides to 40° C. after 40 min. of stirring. To the reaction mixture is added 15 ml of water. The exothermic reaction mixture is cooled by an ice-water bath to 40° C. The cooling bath is removed and the reaction mixture is stirred for 20 min. before being poured into 1 L of water. The organic is extracted into 500 ml of methylene chloride. The methylene chloride extract is dried over magnesium sulfate and concentrated. The residual oil (44.5 g) is purified by HPLC using 5% ethyl acetate in cyclohexane as eluent. The first 2.8 L of eluate gives 7.6 g of an oil which contains 56% of the desired product, 22% of the starting material, and 22% of an unidentified material. The second 2.5 L of eluate gives 24.6 g of an oil which contains a mixture of dimethyl 2-(difluoromethyl)-1,2-dihydro-4-isobutyl-6-(trifluoromethyl)-3,5-pyridinedicarboxylate (E) and dimethyl 6-(difluoromethyl)-1,2-dihydro-4-isobutyl-2-(trifluoromethyl)-3,5-pyridinedicarboxylate (F) and other unidentified products. This oil is crystallized from ether-hexane to give 7.4 g (15%) of a solid, mp 82°-85° C., which is a 4.6:1 mixture of above mentioned (E) and (F). The mother liquor is concentrated to an oil (15.6 g) which contains (E), (F), and other unidentified products. A solution of above oil, 9.0 g (0.0568 mole) of DBU and 100 ml of ether is stirred for 18 hours and washed with 100 ml of 3N hydrochloric acid. The ether solution is dried over magnesium sulfate and concentrated. The residual oil (14.5 g) is purified by HPLC using 5% ethyl acetate in cyclohexane as eluent. The first 2.0 L of eluate gives 8.8 g (19%) of the desired product as an oil, n25D 1.4567. Anal. Calc'd. for C15H17F4NO4 : C, 51.28; H, 4.88; N, 3.99; Found: C, 51.39; H, 4.76; N, 3.85.

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