2-cyano-4-Methylpent-2-enoic acid

Step 1 - 2-Cyano-4-methyl-2-pentenoic acidA stirred suspension of cyanoacetic acid (42.5g, 0.5 mol), ammonium acetate(1 .56g, 0.02 mol, 4 molpercent) and isobutyraldehyde (55ml, 39.66g, 0.55 mol, 1 .1 eq) in toluene (130ml) was heated to reflux with Dean-Stark removal of water. When generation of water ceased, the reaction mixture was cooled to room temperature and concentrated under reduced pressure to give a yellow solid (79.5g). Hexane (150ml) was added and the suspension was stirred at 400rpm for 1 hour. The solid was filtered, washed with hexane (2 x 50ml) and dried to provide the title compound as a yellow crystalline solid (58.5g, 83percent yield).To a solution of 2-cyanoacetic acid (8.7g, 102 mmol) in methanol (200mL) was added 2-methylpropanal (18.6 mL, 204 mmol) and the solution was stirred with a slight exotherm noted. After 30 minutes, added piperidine (1 1.1 mL, 1 12 mmol) and continued stirring for 1 h before removing solvent in vacuo with gentle heating. The thick material was diluted with ether and washed with 125mL of 1.0M HC1 and then washed with brine. The organic phase was dried over sodium sulfate and concentrated to afford a colorless oil weighing 11.2 g of 2- cyano-4-methylpent-2-enoic acid which precipitated on standing.