Abstract
Bonds between arylheteroatom moieties and α-carbons of carboxylic acids are efficiently cleft by azide transfer and subsequent Curtius rearrangement. The scope of the one-pot protocol covers differently substituted carboxylic acids and heteroatoms like O, S, Se, and N.
Key words
azides - cleavage - carboxylic acids - arenes - rearrangement
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General Procedure for the Cleavage Sequence
The substrate (0.60 mmol) is dissolved in anhyd toluene (1.5 mL) and anhyd DMF (0.15 mL). After addition of Et3N (1.01 equiv) and azide-transfer reagent (1.1 equiv, DPPA or DEPA) the mixture was stirred for 30 min at ambient temperature and then brought to reflux for 3 h. Then, KOH solution (0.7 mL, 50 wt% in H2O), EtOH (1.5 mL), and glycerol (0.8 mL) were added to the reaction mixture before refluxing for 2 h. For workup, the reaction mixture was brought to pH 5 by the addition of a sat. citric acid solution. Subsequently, the aqueous layer was extracted with EtOAc (3 25 mL). The combined organic fractions are washed two times with brine (25 mL), dried over MgSO4, and concentrated under reduced pressure. Purification was performed by column chromatography.
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