Preparation of ethyl-N-(diphenylmethylene)-2-acetoxyglycinate: a solution of N-bromosuccinimide (13.9 g, 78 mmol) dissolved in dry DMF (40 ml) was added dropwise at room temperature with stirring over three hours to a mixture of Schiff base 3 (16.05 g, 60 mmol), anhydrous sodium acetate (16.5 g, 201 mmol) and N,N-dimethylformamide (60 ml, distilled from calcium hydride) in a 500 ml round-bottom flask equipped with a magnetic stirrerand a dropping funnel (CaCl 2 ...