Formaldehyde → Ethyl 9-(2,3-Dichlorophenyl)-4,7-dimethyl-1,1-dioxo-2,3,4,5,6,9-hexahydropyrido-[2.3-f][1.41thiazepine-8-carboxylate

Participants

Reaction Steps

A mixture of ethyl 9-(2,3-dichlorophenyl)-1,1-dioxo-2,3,4,5,6,9-hexahydro-7-methylpyrido-[2,3-f][1,4]thiazepine-8-carboxylate (0.500 g, 1.16 mmole) from Example 8, in acetonitrile (10 mL) was treated with formaldehyde (0.240 g, 37% aqueous solution) and sodium cyanoborohydride (0.062 g, 1.16 mmole). After 15 minutes, 6 drops of AcOH were added and the reaction was stirred for 1 hour. Then, 30 mL of water were added and the reaction mixture was extracted with 3×40 mL of chloroform. The pH was adjusted to 8 after the first extract. The combined organic extracts were dried with brine and Na2SO4 and then treated with 3 mL of triethylamine. After standing for 1.5 hours, the volatiles were removed under reduced pressure and the residue chromatographed (silica gel, 1.5% MeOH, 0.1% NH3 in CHCl3) to obtain the product as an oil which solidified on triturating with ether (0.479 g, 92% yield).

Provenance & Evidence