Table 2. Copper foil-catalyzed mechanochemical cyclopropenation of terminal alkynes ^a .

Entry	R1	Product	Isolated yield (%)
1	4-(OCH3)Ph	3	88
2	4-(CH3)Ph	4	95
3	3-(CH3)Ph	5	88
4	4-(C(CH3)3)Ph	6	81
5	4-(F)Ph	7	85
6	4-(Br)Ph	8	85
7	2-(Cl)Ph	9	82
8	3-(Cl)Ph	10	84
9	2,4,6-(CH3)Ph	11	78
10	2-(CH3)-4-(OCH3)Ph	12	90
11	1-Cyclohexenyl	13	86
12	3-Thiophenyl	14	90
13	4-(NH2)Ph	15	94
14 b	Ph	16	81
15 c	Ph	17	Trace e
16 d	Ph	18	Trace e

^aReation conditions: diazoacetate (1.00 eq.), alkyne (5.00 eq.), and copper foil added to a SPEX 8000M mixer/mill (18 Hz) for 16 h.

^b1 eq. of methyl p-bromophenyldiazoacetate was used.

^c1 eq. of ethyl diazoacetate was used.

^d1 eq. of dimethyl diazomalonate was used.

^eRecovered starting material.