Ethyl trans-4,4-dimethyl-5-hydroxypent-2-enoate → Ethyl 4-methyl-4-formylpent-2-enoate

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Ethyl trans-4,4-dimethyl-5-hydroxypent-2-enoate (8.6 g, 0.05 mol) in 100 ml of dichloromethane was added to a stirred suspension of 70 g (0.27 mol) of chromium trioxide-pyridine complex in 900 ml of anhydrous dichloromethane. The insoluble black gum residue was washed thoroughly three times with 100-ml portions of ether. The combined organic solutions were passed through a column (3.5-cm 25-cm) of Silicagel and the solvent was removed by distillation. Distillation of the residue oil through a 20-cm Widmer column gave 8.0 g (94%) of ethyl 4-methyl-4-formylpent-2-enoate. b.p. 110 111° C./15 Torr, nD 18 1.4605. 1H NMR (CDCl3): (=1.30 [s, 6H, C(CH3)2], 1.45 (t, 3H, CH3CH2), 4.15 (q, 2H, CH2CH3), 5.85 (d, 1H, J=16 Hz, 3-H), 6.90 (d, 1H. J=16 Hz, 2-H), 9.45 (s, 1H, CHO). Anal. Calcd. for C9H14O3: C, 63.51; H, 8.29. Found: C, 63.53; H, 8.38.

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