(i) LDA, (ii) /BRN= 385735/, (iii) oxalic acid; Multistep reaction;

water; tert.-butyl lithium; oxalic acid 1) THF, -78 degC, 2 h; 2) THF, 5 degC, 30 min; Yield given. Multistep reaction. Yields of byproduct given;