Trifluoroacetic acid → (3S)-6-Chloro-3-methyl-4-(3-methyl-2-butenyl)-3,4-dihydro-1,4,5-triazanaphthalen-2(1H)-one

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Reaction Steps

The compound of Example 2 (988 mg, 5.0 mmol) was suspended in 40 ml of anhydrous 1,2-dichloroethane. While stirring, 840 mg (10 mmol) of 3,3-dimethylacrolein and subsequently 1.9 ml (25 mmol) of trifluoroacetic acid were added. The mixture was cooled in an ice bath, 2.1 g (10 mmol) of sodium triacetoxyborohydride were introduced in portions, and the mixture was stirred at 0° C. for 1 h and at room temperature for a further 3 h. The reaction mixture was then added to about 150 ml of saturated aqueous sodium bicarbonate solution, the phases were separated, the aqueous was back-extracted three times with dichloromethane, and the combined organic extracts were dried (sodium sulfate) and concentrated. Chromatography on silica gel (ethyl acetate/heptane=1:2) provided 650 mg (49%) of the desired compound as a crystalline solid of melting point 136°-137° C.

Provenance & Evidence