Abstract
Di-tert -butyl acylimidodicarbonates, prepared from primary amides with two equivalents of di-tert -butyl dicarbonate under catalysis by 4-dimethylaminopyridine, readily undergo selective reductive cleavage of their acyl CO-N bonds by NaBH4 to provide the corresponding alcohols in high yields.
Key words
alcohols - amides - cleavage - reductions - sodium borohydride
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Typical Reduction Procedure: A solution of 2c (732 mg, 2 mmol) in abs EtOH (12 mL) was treated with an excess of NaBH4 (151 mg, 4 mmol) in one batch. After 20 h, when all starting material had been consumed (TLC monitoring), acetone (1 mL) was added, whereupon after 1 h the solvent was evaporated. The obtained foam was dissolved in Et2 O/H2 O, the aqueous phase backwashed once with Et2 O and the combined extracts dried (Na2 SO4 ). After evaporation the mixture was purified by chromatography on silica gel (eluent: Et2 O/CH2 Cl2 1:15). HNBoc2 eluted first, followed by pure 3c (298 mg, 97%); mp 91-92 °C; it was recrystallized from Et2 O/light petroleum.
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