Dimethylformamide dimethyl acetal → ethyl 3-cyano-2-[(E)-dimethylaminomethylideneamino]-5,7-dihydro-4H-furo[2,3-c]pyridine-6-carboxylate

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Reaction Steps

Ethyl 2-amino-3-cyano-4,7-dihydrofuro[2,3-c]pyridine-6(5H)-carboxylate from Example 36A (7.00 g, 29.8 mmol) was heated in dimethylformamide dimethylacetal (14.7 mL, 110 mmol) for 30 min to 110° C. The mixture was then concentrated in vacuo, and the residue was triturated with petroleum ether, the solvent was decanted, and the trituration was repeated. The remaining solid was then triturated with diethyl ether/petroleum ether (1:1), and the precipitate was collected by suction filtration to yield 8.5 g (98%) of the title compound.

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