C[O-].[Na+].CO.[C:6](=[O:11])([O:9][CH3:10])OC.[Cl:12][C:13]1[CH:14]=[C:15]([CH2:20][C:21]([O:23][CH3:24])=[O:22])[CH:16]=[C:17]([Cl:19])[CH:18]=1.C(O)(=O)C>C1(C)C=CC=CC=1.O>[Cl:12][C:13]1[CH:14]=[C:15]([CH:20]([C:6]([O:9][CH3:10])=[O:11])[C:21]([O:23][CH3:24])=[O:22])[CH:16]=[C:17]([Cl:19])[CH:18]=1
A mixture sodium methoxide in methanol (28.46 g, 25%, 0.132 mol) and toluene (150 mL) was boiled with provision of a five plate Oldershaw column to remove the methanol/toluene azeotrope. The mixture was cooled to 60° C. and toluene (a volume equal to the total volume of the distillate) was added to the mixture. Dimethyl carbonate (35.95 g, 0.399 mol) was added to the reaction mixture. Methyl 3,5-dichlorobenzeneacetate (i.e. the product from Step A1b) (22.2 g, 0.101 mol) in toluene (17 mL) was added to the mixture over 70 min. When the addition was complete the mixture was stirred for a further 60 min at 60° C. The mixture was boiled and the dimethyl carbonate/methanol azeotrope was removed using the Oldershaw column. The mixture was cooled to 25° C. and acetic acid (9.5 g, 0.158 mol) was added dropwise. Water (100 mL) was added to the mixture and the organic phase separated and removed under reduced pressure. Crystallisation of the resulting residue from methanol (36 mL) gave the product as a white solid (23.9 g, 85%) melting at 72-73° C.
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