Table 3.

Influence of the phosphine oxide ligands on the catalyst performance in the N-oxidation of 1^a

Entry	Ligand	TON
1b	H3PO4	11
2	Ph3PO	12
3	(p-FC6H4)3PO	14.6
4	[3,5-(CF3)2C6H3]3PO	6.9
5	Me2PhPO	7.5
6	tBuPh2PO	8.9
7	(o-Tol)3PO	1.8
8	o-C6H4(PPh2O)2	1
9	Et3PO	12.9
10	(Me2N)3PO	8.1
11c	dppe-dioxide	3.9
12c	dppm-dioxide	2.2
13c	binap-dioxide	2.1

^aReaction conditions: 1 (1.4 mmol), MoO₃ (5 mol%), ligand (5 mol%) CH₃CN (1 mL), H₂O₂ (30% aq. solution, 4 equiv.), 50 °C, 4 h.

^b1.25 mol% H₃PO₄ was used.

^cdppe = 1,2-bis(diphenylphosphino)-ethane, dppm = bis(diphenylphosphino)methane, binap = 2,2′-bis-(diphenylphosphino)-1,1′-binaphthyl.