1-Chloro-N,N-2-trimethylpropenylamine → N-(7-bromo-3-chloro-5',6'-dihydrospiro[chromeno[2,3-c]pyridine-5,4'-[1,3]thiazin]-2'-yl)-4-nitrobenzamide hydrochloride

1-Chloro-N,N,2-trimethylprop-1-en-1-amine (2.84 ml, 21.28 mmol) was added to a solution of N-((7-bromo-3-chloro-5-(2-hydroxyethyl)-5H-chromeno[2,3-c]pyridin-5-yl)carbamothioyl)-4-nitrobenzamide (12 g, 21.28 mmol) in DCM (200 ml). The reaction mixture was stirred at RT for 8 hours and then concentrated under reduced pressure to 50% of its original volume. A precipitate formed upon cooling which was filtered off, washed with DCM and then dried under reduced pressure to afford N-(7-bromo-3-chloro-5′,6′-dihydrospiro[chromeno[2,3-c]pyridine-5,4′-[1,3]thiazin]-2′-yl)-4-nitrobenzamide hydrochloride (10.5 g, 18.03 mmol, 85% yield) as an off white solid.