Trimethyl orthoformate → 2-Chloro-6-((4-(methylsulfonyl)piperazin-1-yl)methyl)-4-morpholinothieno[2,3-d]pyrimidine

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Reaction Steps

Scheme 7 shows the synthesis of 4-(2-chloro-6-((4-(methylsulfonyl)piperazin-1-yl)methyl)thieno[2,3-d]pyrimidin-4-yl)morpholine 20 by formylation of 4-(2-chlorothieno[2,3-d]pyrimidin-4-yl)morpholine 18 in THF at −78° C. with n-BuLi in hexanes (1.2 equiv.). The resulting slurry was allowed to warm up to −60° C., cooled to −78° C. and DMF (1.5 equiv.) was added slowly to afford 2-chloro-4-morpholinothieno[2,3-d]pyrimidine-6-carbaldehyde 19. To a suspension of 19, 4-(methylsulfonyl)piperazin-1-ium chloride 8 (alternatively named as 1-(methylsulfonyl)piperazine hydrochloride, 1.45 equiv.) and anhydrous sodium acetate in 1,2-dichloroethane was added trimethyl orthoformate (10 equiv.). The slurry was stirred at ambient temperature for at least 6 hours, then sodium triacetoxyborohydride was added and the reaction was stirred for 24 hours to give 20.

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