Hydrochloric Acid → 2-Ethyl-3-methoxybenzaldehyde

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To a solution of 2,2,6,6-tetramethylpiperidine (4.67 g, 33 mmol) in 75 ml THF at −15° C. was added n-butyllithium (12.6 ml, 32 mmol, 2.5 in hexanes) drop-wise maintaining the internal temperature below −10° C. After 15 min a solution of cyclohexyl-(3-methoxy-benzylidene)-amine (3.259 g, 15.0 mmol) in 5.0 ml THF was added and the solution was allowed to stir at −15° C. After 1 h the solution was cooled to −78° C. Iodoethane (11.9 ml, 150 mmol) was added in one portion and the solution was allowed to warm to rt over 45 min, poured into 10% NH4Cl, and extracted with Et2O. The combined organics were washed with H2O, washed with brine, dried over MgSO4, filtered and concentrated in vacuo to give a crude imine as an oil. The oil was taken up in 90 ml of THF and HCl (22 ml, 89 mmol, 4.0 M) and warmed to reflux. After 2 the solution was cooled. H2O was added and the mixture was extracted with ethyl acetate. The combined organics were washed with H2O, washed with brine, dried over Na2SO4, filtered and concentrated in vacuo to give a crude oil. Purification via flash chromatography (98:2 hexane/ethyl acetate) gave 2-ethyl-3-methoxy benzaldehyde (1.543 g, 63%, 2 steps) as a clear oil.

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