Table 3. Optimisation of the catalysts.

Entry	Catalyst	4 yield (%)	Entry	Catalyst	4 yield (%)
1	PTA	6.34	12	10i	1.79
2	PMA	7.05	13	10j	2.13
3	HPC	5.47	14	10k	1.47
4	10a	7.77	15	10l	4.54
5	10b	4.78	16	10m	10.40
6	10c	2.03	17	10n	12.30
7	10d	8.03	18	10o	14.11
8	10e	5.07	19	10p	18.20
9	10f	1.98	20	10q	16.78
10	10g	5.47	21	10r	11.79
11	10h	6.13

*Reaction conditions: 1 (10 mmol), catalyst (0.1 equiv), 1,4-dioxane (7 mL), H₂O₂ (5 mL), 70 °C, 2 h; then 90 °C, 1h; GC yield; HPC (Dowson-type H₆P₂W₁₈O₆₂).