Triethylamine → 8-Benzyloxycarbonyl-1,4-dioxa-8-aza-spiro[4.5]decane-6-carboxylic acid methyl ester

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Reaction Conditions

Reaction Steps

Triethylamine (29.0 mL, 208 mmol) was added to a solution of 1,4-dioxa-8-aza-spiro[4.5]-decane-6-carboxylic acid methyl ester (91) (16.6, 82.5 mmol) in CH2Cl2 (159 mL, 0.5 M). The solution was cooled to 0° C. in an ice bath, then benzoylchloroformate (12.8 mL, 89.9 mmol) was added dropwise, with stirring, over 40 minutes. When the reaction was judged complete by TLC (0.75 h), the solution was concentrated in vacuo and purified by silica gel chromatography (10:3 Hexanes:EtOAc) to provide pure 8-benzyloxycarbonyl-1,4-dioxa-8-aza-spiro[4.5]-decane-6-carboxylic acid methyl ester (92) (23.43 g, 85%). 1H NMR (CDCl3): 7.41–7.25 (5H, m), 5.10 (2H, broad s), 4.02–3.50 (11 H, m), 2.80–2.62 (1H, broad s), 2.20–2.00 (1H, broad s), 1.70–1.50 (1H, broad s) ppm. 13 C NMR (CDCl3): 170.26, 154.88, 136.47, 128.32, 127.86, 127.74, 106.78, 67.09, 64.90, 64.59, 51.71, 48.63, 43.94, 41.76, 33.15 ppm.

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