Table 3.

C–H oxidation of tetrahydrofuran 20

Entry	Conditions	Yield of 22 a
1	CrO3, AcOH, rt	0% (23: 35%)
2	RuCl3, NaIO4,CCl4–MeCN–pH7 buffer, rt	0% (23: 7%, 24: 33%)
3	(S,S)-Fe(pdp), AcOH, aq. H2O2, rt	65%
4	DMDO, CH2Cl2, rt	22% (30% brsm)
5	TFDO, CH2Cl2, 0 °C	24% (23: 36%)
6	TFDO, CH2Cl2, −78 °C	96%

DMDO, dimethyldioxirane, pdp, N,N’-bis(2-pyridylmethyl)]-2,2′-bipyrrolidine, TFDO, methyl(trifluoromethyl)dioxirane

^aIsolated yield