Synthesis of Diazo Compounds

Diazo compounds are remarkably versatile intermediates in organic synthesis. Recently, Raines et al. have reported the conversion of azides into diazo compounds using N-succinimidyl 3-(diphenylphosphino)propionate (1). According to their results, azides react with 1 to give alkyl acyl triazenes in THF–H₂O. Subsequent base-catalyzed fragmentation affords the corresponding diazo compounds in high yields. This is useful as a mild and convenient method for the synthesis of diazo compounds. Their broad future application is expected.

Typical Procedure:
2-Azido-N-benzylacetamide (57 mg, 0.300 mmol) is dissolved in THF/H₂O (2 mL/300 μL). To this solution is added phosphine 1 (112 mg, 0.315 mmol), and the resulting solution is stirred for 4 h under Ar. Sat. aq. NaHCO₃ (2 mL) is then added, and the mixture is stirred vigorously for 4 h. The mixture is then diluted with sat. aq. NaCl (15 mL) and extracted with CH₂Cl₂ (2 × 15 mL). The organic layers are combined, dried over Na₂SO₄, filtered, and evaporated under reduced pressure. The residue is purified by silica gel flash chromatography (hexane : EtOAc = 7 : 3), to give the diazo compound as a yellow solid (45 mg, 0.255 mmol, Y. 85%).