sodium carbonate in methanol; water T=-20°C; 0.25 h;

1: 5,5-dibromo-2,2-dimethyl-4,6-dioxo-1,3-dioxan 2: 1) sodium formate, 2) ammonium hydroxide / 1) acetonitrile, 30 min, reflux, 2) MeOH, 30 min, 25 degC View Scheme

ammonium hydroxide; sodium formate 1) acetonitrile, 30 min, reflux, 2) MeOH, 30 min, 25 degC;