3-hydroxy-5,5-dichloro-2,4-pentadienoic-acid-morpholide 2.875g (11.40mmol) was suspended in anh. dioxane 20mL under Ar and neat triflic acid 3.05mL (34.5mmol) was added. The mixture was stirred at 80C (oil bath) for 6 hours. The mixture was cooled, solid Na2CO3 4.1g was added with cooling on ambient bath, followed by water 40mL (CO2 evolution). The mixture was extracted twice with dichloromethane (2x150mL), the extracts were washed with brine 40mL, combined, dried (MgSO4) and evaporated. The solid residue was re-crystallized from a mixture of benzene 50mL and hexane 60mL. (The mixture was allowed to cool to RT, carefully decanted from a small amount of sticky gum, inoculated mechanicaly and allowed to crystallize for 12 hours at RT then in fridge at +5C overnight, 10 hours). The supernatants were decanted, the obtained light tan fluffy needles (1.737g) were washed with hexane and dried on highvac. Evaporating the supernatants and re-crystallizing the residue provided additional 270mg of pure product. Combined Y=2.007g (81.5%) of a light tan crystalline solid.
1H(d6-DMSO, 400MHz): 6.237(d, 1.7Hz), 5.402(d, 1.7Hz), 3.665(app t, 4.8Hz, 4H), 3.310(app t, 4.8Hz, 4H)