Methyl morpholine oxide → (2E)-3-methyl-2-heptenal

To a suspension solution of alcohol 13b (739 mg, 5.7 mmol), 4 A molecular sieves (2.9 g, activated), and NMO (1.33 g, 11.4 mmol) in CH2Cl2 (12 mL) at 0° C., was added TPAP (120 mg, 0.34 mmol) in one-portion. The resulting dark reaction mixture was allowed to stir at 0° C. for 30 min, before being diluted with CH2Cl2 (20 mL), and then filtered through a short pad of silica gel. The filtrate was concentrated in vacuo to afford aldehyde 14c (704 mg, 98% yield) as a colorless oil. The aldehyde is sufficiently pure for immediate use without further purification: 1H NMR (400 MHz, CDCl3) δ 9.94 (d, J=8.1 Hz, 1H), 5.82 (d, J=8.1 Hz, 1H), 2.16 (t, J=7.6Hz, 2H), 2.11 (s, 3H), 1.44 (m, 2H), 1.28 (m, 2H), 0.87 (t, J=7.3 Hz, 3H); 13C NMR (75 MHz, CDCl3) δ 191.3, 164.5, 127.2, 40.3, 29.2, 22.3, 17.4, 13.8; IR (neat) δ max: 2959, 2933, 2863, 1676, 1467, 1195, 1131 cm−1.