Electronic Impacts on the Solvent-Free Mechanochemical Synthesis of Salophen Ligands in Ball Mill

Table 1

Optimization of the mechanochemical ball milling conditions for Salophen synthesis^a.

Entry	Time (min)	Frequency (Hz)	Ball type	Ball size (mm)	Ball number	Jar type (10 ml)	Yield (%)^b
1	20	30	SS	10	1	Teflon	64
2	40	30	SS	10	1	Teflon	72
3	60	30	SS	10	1	Teflon	90 [86^c]
4	80	30	SS	10	1	Teflon	74
5	100	30	SS	10	1	Teflon	80
6	120	30	SS	10	1	Teflon	74
7	60	25	SS	10	1	Teflon	63
8	60	20	SS	10	1	Teflon	64
9	60	15	SS	10	1	Teflon	62
10	60	10	SS	10	1	Teflon	45
11	60	30	ZrO2	10	1	Teflon	78
12	60	30	WC	10	1	Teflon	63
13	60	30	SS	Blank	1	Teflon	27
14	60	30	SS	5	1	Teflon	67
15	60	30	SS	7	1	Teflon	67
16	60	30	SS	12	1	Teflon	75
17	60	30	SS	5	2	Teflon	69
18	60	30	SS	7	2	Teflon	64
19	60	30	SS	7	3	Teflon	64
20	60	30	SS	10	2	Teflon	61
21	60	30	SS	10	1	SS	61

^aReaction conditions: 1 mmol (1) and 1 mmol (2a) were milled in a mixer mill; ^byield based on ¹H NMR analysis of the crude reaction mixture taken directly from the milling jar; ^cisolated yield; SS: stainless steel.