Reaction Steps
To a solution of 6-(5-formyl-2-nitro-phenoxy)-hexanoic acid ethyl ester (1.0 g, 3.23 mmol) in ethanol (20 ml) and concentrated HCl (5 ml) was added stannous chloride (2.17 g, 11.63 mmol). The mixture was stirred at 70° C. for 90 minutes while being monitored by thin layer chromatography. After cooling to room temperature, the mixture was poured into water (100 ml) and neutralized with a saturated solution of sodium bicarbonate resulting in the precipitation of tin salts and a dark brown oil. The salts were washed with ethyl acetate and the washings were combined with the original filtrate, the aqueous phase was separated and the remaining ethyl acetate phase was dried with magnesium sulfate, filtered and concentrated by rotary evaporation to a brown oil which was purified by column chromatography (45% CH2Cl2, 45% hexane, 10% Et3N). The product, 6-(2-amino-5-formyl-phenoxy)-hexanoic acid ethyl ester, was obtained as a red oil (0.33 g, 35%). An additional 0.32 g of red oil was obtained from the column but found to be a mixture of unidentified byproducts. 1H NMR (400 MHz, CDCl3) δ: 9.72 (s, 1H), 7.30 (m, 2H), 6.73 (d, 1H, J=8.4 Hz), 4.50 (s, 2H), 4.15 (q, 2H, J=7.2 Hz), 4.08 (t, 2H, J=6.8 Hz), 2.35 (t, 2H, J=8.8 Hz), 1.88 (m, 2H), 1.74 (m, 2H), 1.55 (m, 2H) 1.30 (t, 3H, J=6.8 Hz). 13C NMR (400 MHz, CDCl3) δ: 109.59, 173.60, 146.08, 143.31, 127.78, 127.55, 112.72, 109.11, 68.18, 60.35, 34.20, 28.83, 25.69, 24.61, 14.18. IR (neat): 3481, 3362, 2936, 2868, 2722, 2360, 2341, 2229, 2156, 1964, 1727, 1671, 1612, 1587, 1572, 1517, 1444, 1394, 1368, 1313, 1243, 1164, 1140, 1095, 1029, 864, 817, 789, 748.
