Table 4.

Thermal cycloaddition of sydnones with terminal alkynes.

entry	R1	R2	R3	conditions	ratio 1,3:1,4	yield [%]a	ref.
1	Ph	Me	n-Hex	xylene, 140 °C, 30 h	n.d.	78	[1]
2	Ph	H	n-Hex	toluene, 111 °C, 52 h xylene, 160 °C, 24 h	n.d. 90:10	72 65	[2] [91]
3	Ph	H	Ph	chlorobenzene, 120 °C, 20 h xylene, 140 °C, 16 h o-DCB, μ-wave, 200 °C, 2 h o-DCB, 140 °C, 24 h	n.d. >95:5 91:9 91:9	79/<2 35 66 62	[1–2] [82] [84] [92]
4	Ph	Me	Ph	140 °C, 12 h 142 °C, 7 h	~80:20 ~89:11	64/15 73/9	[1] [2]
5	Bn	H	Ph	xylene, 135–140 °C, 20 h	100:0	69–74	[1–2]
6	Ph	H	COOMe	xylene, 100 °C, 48 h sc-CO2, 60–160 °C, 7.6 MPa	76:24 85:15–76:24	70/22 –	[1–2] [93]
7	Ph	Me	COOMe	140 °C, 4 h xylene, reflux, 1 h	n.d. 65:35	61/10 55/29	[1] [2]
8	Ph	H	CH(OPr)2	xylene, 135–140 °C, 3 h	n.d.	28/58	[2]
9	Ph	Me	CH(OPr)2	xylene, 135–140 °C, 15 h	n.d.	77	[1]
10	Bn	H	CH(OPr)2	xylene, 135–140 °C, 15 h	n.d	78	[2]
11	Ph	H	CH2OH	reflux, 24 h	100:0	66–72	[1–2]
12	Ph	H	CN	chlorobenzene, 110 °C, 24 h	100:0	50	[66]
13	NMe2	H	Ph	tetraline, reflux, 5 h	n.d.	60/–	[67]
14	NMe2	H	4-Cl-Ph	tetraline, reflux, 5 h	n.d.	23/–	[67]
15	NMe2	H	4-Me-Ph	tetraline, reflux, 5 h	n.d.	32/–	[67]
16	NMe2	H	n-Hex	tetraline, reflux, 5 h	n.d.	50/–	[67]
17	O(CH2CH2)2N	H	Ph	tetraline, reflux, 5 h	n.d.	22/–	[67]
18	(CH2)5N	H	4-Cl-Ph	tetraline, reflux, 5 h	n.d.	24/1	[67]
19	NMe2	Me	Ph	tetraline, reflux, 5 h	n.d.	81/10	[67]
20	NMe2	Me	4-Cl-Ph	tetraline, reflux, 5 h	n.d.	30/4	[67]
21	NMe2	O(CH2CH2)2NCH2	Ph	tetraline, reflux, 5 h	n.d.	34/2	[67]
22	NMe2	O(CH2CH2)2NCH2	4-Cl-Ph	tetraline, reflux, 5 h	n.d.	12/2	[67]
23	Ph	MeS	COOMe	toluene, 95–105 °C, 12.5 h	46:54	39/50	[8]
24	Ph	PhS	COOMe	xylene, 140 °C, 35 h	53:47	95	[8]
25	Ph	MeSO	COOMe	mesitylene, 135–140 °C, 19 h	81:19	65/15	[8]
26	Ph	MeCO	COOMe	mesitylene, 155–160 °C, 90 h	60:40	46/37	[8]
27	Ph	Ph	COOMe	xylene, 110–115 °C, 12 h o-DCB, reflux, 48 h	50:50 50:50	40/44 97	[8] [80]
28	4-NO2-Ph	Ph	COOMe	toluene, 95–105 °C, 16 h	56:44	51/37	[8]
29	2,4-diNO2-Ph	Ph	COOMe	toluene, 100–105 °C, 18.5 h	61:39	55/36	[8]
30	4-NO2-Ph	H	COOMe	toluene, 95–105 °C, 4 h	86:14	99	[8]
31	Ph	H	PhSO2	toluene, 100 °C, 24 h	25:75	56	[68]
32	CH2CH2CH2		Ph	xylene	≈75:25	51/18	[69]
33	Ph	I	COOMe	xylene, reflux, 24 h	58:42	n.d.	[20]
35	2-Et-Ph	I	COOMe	xylene, reflux, 24 h	56:44	n.d.	[20]
36	Me	H	COOMe	toluene, reflux, 12 h	100:0	75	[70]
37	CH2CH2CH2CH2		COOMe	xylene, reflux, 10 h xylene, reflux, 16 h xylene, reflux, 6 h	67:33 n.d. n.d.	60 65/26 56/–	[71] [77] [83]
38	CH2CH2CH2CH2		COOEt	xylene, reflux, 10 h	75:25	75	[71]
39	CH2CH2CH2CH2		COOn-Bu	xylene, reflux, 10 h	63:37	72	[71]
40	CH2CH2CH2CH2		COOBn	xylene, reflux, 10 h	69:31	59	[71]
41	CH2CH2CH2CH2		COO(1-PhEt)	xylene, reflux, 10 h	66:34	60	[71]
42	4-Br-2-Et-Ph	I	COOEt	xylene, reflux, 24 h	–	–	[24]
43			COOMe	o-xylene, reflux, 15 h	n.d.	68/12	[72,77]
44	CH2SCH2		COOMe	o-xylene, reflux, 19 h xylene, reflux, 4 h	n.d.	49/22 53/21	[72–73] [36]
45			COOMe	o-xylene, reflux, 16 h	n.d.	64/24	[72,77]
46			COOMe	o-xylene, reflux, 16 h	n.d.	32/32	[72]
47			COOMe	o-xylene, reflux, 16 h o-xylene, reflux, 15 h	n.d.	59/34 68/12	[72] [73]
48			COOMe	o-xylene, reflux, 21 h	40:60	80	[72]
49	CH2CH2CH2		COOMe	xylene, reflux, 8 h 1,2-diethoxyethane, 120–125°C, 8 h	n.d. ≈87:13	40/35 47	[13] [74]
50	4-EtO-Ph	H	COOEt	chlorobenzene, reflux, 48 h	76:24	90	[75]
51	4-EtO-Ph	I	COOEt	chlorobenzene, reflux, 48 h	56:44	81	[75]
52	4-EtO-Ph	CN	COOEt	chlorobenzene, reflux, 48 h	58:42	80	[75–76]
53	4-EtO-Ph	CH2OH	COOEt	chlorobenzene, reflux, 48 h	63:37	71	[75]
54	4-EtO-Ph	PhS	COOEt	chlorobenzene, reflux, 48 h	52:48	71	[75]
55	4-EtO-Ph	CN	COOBn	chlorobenzene, reflux, 48 h	57:43	76	[75–76]
56	4-EtO-Ph	CN	COOt-Bu	chlorobenzene, reflux, 48 h	78:22	79	[75–76]
57	4-EtO-Ph	CN	COOCHPh2	chlorobenzene, reflux, 48 h	100:0	85	[75–76]
56a	Ph	CN	COOCHPh2	chlorobenzene, reflux, 48 h	100:0	80	[75–76]
57a			COOMe	o-xylene, reflux, 21 h	n.d.	87	[77]
58	2,3-diMe-Ph	H	COOMe	xylene, reflux, 12 h	75:25	n.d.	[28]
59	Ph	H	Me3Si	toluene, reflux	n.d.	95/–	[78]
60	Ph	H	Me2PhSi	toluene, reflux	n.d.	80/–	[78]
61	Ph	H	t-BuPh2Si	toluene, reflux	n.d.	15/–	[78]
62	Ph	H	BPin	mesitylene, reflux, 16 h	88:12	47/7	[79,81]
63	Ph	Ph	4-(Me2N)-Ph	o-DCB, reflux, 48 h	n.d.	65/–	[80]
64	4-NO2-Ph	Me	BPin	o-DCB, reflux, 24 h	89:11	79	[81]
65	4-NO2-Ph	iPr	BPin	o-DCB, reflux, 24 h	>98:2	75	[81]
66	CH2CH2CH2CH2		BPin	xylene, reflux, 24 h	90:10	78	[81]
67	4-NO2-Ph	H	Ph	xylene, 140 °C, 8 h	95:5	60	[82]
68	4-NO2-Ph	I	Ph	xylene, 140 °C, 8 h	91:9	84	[82]
69	Ph	I	Ph	xylene, 140 °C, 16 h	>95:5	73	[82]
70	4-MeO-Ph	H	Ph	xylene, 140 °C, 24 h o-DCB, 140 °C, 24 h	91:9 91:9	30 76	[82] [92]
71	4-MeO-Ph	I	Ph	xylene, 140 °C, 24 h	91:9	72	[82]
72	4-NO2-Ph	H	Me3Si	xylene, 140 °C, 8 h	89:11	75b	[82]
73	4-NO2-Ph	I	Me3Si	xylene, 140 °C, 8 h	95:5	99b	[82]
74	4-NO2-Ph	H	n-Bu	xylene, 140 °C, 8 h	91:9	47b	[82]
75	4-NO2-Ph	I	n-Bu	xylene, 140 °C, 8 h	91:9	82b	[82]
76	4-NO2-Ph	I	Bn	xylene, 140 °C, 8 h	91:9	64b	[82]
77	4-NO2-Ph	I	cyclo-Pr	xylene, 140 °C, 8 h	94:6	77b	[82]
78	4-NO2-Ph	I	CH2OBn	xylene, 140 °C, 8 h	>95:5	62b	[82]
79	4-NO2-Ph	I	C(OH)Ph2	xylene, 140 °C, 8 h	>95:5	70b	[82]
80	4-NO2-Ph	I	4-MeO2C-Ph	xylene, 140 °C, 8 h	>95:5	65b	[82]
81	3-Py	H	Ph	o-DCB, μ-w, 200 °C, 2 h	89:11	84	[84]
82	Ph	H	2-Py 2-PyH+ TsO–	o-DCB, μ-w, 200 °C, 2 h ethylene glycol, reflux, 16 h	60:40 91:9	85 14	[84]
83	3-Py	H	2-Py	o-DCB, μ-w, 200 °C, 2 h	67:33	80	[84]
84	Ph	H		o-DCB, μ-w, 200 °C, 2 h	60:40	86	[84]
85	3-Py	H		o-DCB, μ-w, 200 °C, 2 h	60:40	84	[84]
86	4-NO2-Ph	Me	2-Py	o-DCB, reflux, 20 h	80:20	87	[84]
87	4-NO2-Ph	iPr	2-Py	o-DCB, reflux, 20 h	86:24	78	[84]
88	4-NO2-Ph	iPr		o-DCB, reflux, 20 h	n.d.	66/19	[84]
89	3-Py	H	BPin	mesitylene, reflux, 16 h	89:11	84	[84]
90	CH2CH2CH2		4-F-Ph	mesitylene, 155–160 °C, 16 h	n.d.	27/–	[85]
91	Ph	CF3	Ph	o-DCB, 180 °C, 24 h	94:6	87	[32–33]
92	Ph	CF3	cyclo-Pr	o-DCB, 180 °C, 24 h	>98:2	88	[32–33]
93	Ph	CF3	Me3Si	o-DCB, 180 °C, 24 h	>98:2	75	[32–33]
94	Ph	CF3	2-Py	o-DCB, 180 °C, 24 h	95:5	84	[32–33]
95	Ph	CF3	BnOCH2	o-DCB, 180 °C, 24 h	96:4	84	[32–33]
96	Ph	CF3	2-F-4-Cl-5-Me-Ph	o-DCB, 180 °C, 24 h	n.d.	86/–	[32]
97	Ph	CF3	Bu	o-DCB, 180 °C, 24 h	>98:2	78	[33]
98	Ph	CF3		o-DCB, 180 °C, 24 h	>98:2	89	[33]
99	Ph	CF3	(CH2)3Cl	o-DCB, 180 °C, 24 h	98:2	70	[33]
100	4-MeO-Ph	CF3	Ph	o-DCB, 180 °C, 24 h	>98:2	85	[33]
101	4-MeO-Ph	CF3	Bu	o-DCB, 180 °C, 24 h	>98:2	71	[33]
102	4-MeO-Ph	CF3	cyclo-Pr	o-DCB, 180 °C, 24 h	>98:2	75	[33]
103	4-NO2-Ph	CF3	Ph	o-DCB, 180 °C, 24 h	>98:2	85	[33]
104	4-NO2-Ph	CF3	(CH2)3Cl	o-DCB, 180 °C, 24 h	>98:2	68	[33]
105	Me	CF3	Ph	o-DCB, 180 °C, 24 h	98:2	95	[33]
106	Me	CF3		o-DCB, 180 °C, 24 h	98:2	82	[33]
107	Me	CF3	BnOCH2	o-DCB, 180 °C, 24 h	>98:2	89	[33]
108	Me	CF3	COOEt	o-DCB, 180 °C, 24 h	93:7	94	[33]
109	Ph	CF3	BPin	o-DCB, 140 °C, 72 h	93:7	69	[32–33]
110	Me	CF3	BPin	o-DCB, 140 °C, 72 h	96:4	44	[33]
111	Bn	CF3	Ph (2 equiv) Ph (2 equiv) Ph (2 equiv) Ph (10 equiv)	o-DCB, 180 °C, 24 h o-DCB, 140 °C, 24 h o-DCB, 140 °C, 48 h o-DCB, 180 °C, 24 h	64:36 96:4 88:12 88:12	61 34 66 64	[33]
112	Bn	CF3	Bu	o-DCB, 180 °C, 24 h	72:28	48	[33]
113	Ph	CH2OH	Ph	o-DCB, 180 °C, 24 h	n.d.	72/–	[33]
114	Ph		COOEt	o-DCB, 180 °C, 30 min, μ-wave	88:12	66	[34]
115	Ph		Ph	xylene, 140 °C, 6 h, μ-wave	98:2	51	[34]
116	Ph		Me3Si	xylene, 140 °C, 3.5 h, μ-wave	98:2	17	[34]
117	4-MeO-Ph		COOEt	o-DCB, 180 °C, 1 h, μ-wave	83:17	44	[34]
118	Bn		COOEt	o-DCB, 180 °C, 30 min, μ-wave	67:33	21	[34]
119	Ph	H		toluene, reflux, 12 h	100:0	33	[86]
120	4-Me-Ph	H		toluene, reflux, 12 h	100:0	35	[86]
121	4-I-Ph	H		toluene, reflux, 12 h	100:0	40	[86]
122	4-Cl-Ph	H		toluene, reflux, 12 h	100:0	43	[86]
123	4-F-Ph	H		toluene, reflux, 12 h	100:0	38	[86]
124	4-MeO-Ph	H		toluene, reflux, 12 h	100:0	33	[86]
125	3,4-OCH2O-Ph	H		toluene, reflux, 12 h	100:0	30	[86]
126	Ph	H		toluene, reflux, 12 h	≈34:67	18/36	[86]
127	4-Me-Ph	H		toluene, reflux, 12 h	≈40:60	28/42	[86]
128	4-I-Ph	H		toluene, reflux, 12 h	≈80:20	20/5	[86]
129	4-Cl-Ph	H		toluene, reflux, 12 h	≈83:17	35/4	[86]
130	4-F-Ph	H		toluene, reflux, 12 h	≈67:33	20/10	[86]
131	4-MeO-Ph	H		toluene, reflux, 12 h	≈20:80	10/40	[86]
132	3,4-OCH2O-Ph	H		toluene, reflux, 12 h	≈67:33	20/10	[86]
133			CF3	o-xylene, −78–270 °C, 12 h	n.d.	61/10	[87]
134	Ph	H	3,5-di-HC≡C-Ph	N-methylpyrrolidone, 185 °C, 48 h	n.d.	(32)	[88]
135	3,4,5-tri-MeO-Ph	3-BnO-4-MeO-Ph	Me3Si	xylene, 160 °C, 24 h	95:5	74	[89]
136	3-BnO-4-MeO-Ph	3,4,5-tri-MeO-Ph	Me3Si	xylene, 160 °C, 24 h	95:5	79	[89]
137	Me	H	3,4,5-tri-MeO-Ph	xylene, 160 °C, 24 h	>98:2	88	[89]
138	Bn	H	3,4,5-tri-MeO-Ph	xylene, 160 °C, 24 h	90:10	65	[89]
139	Me	H	3-TBSO-4-MeO-Ph	xylene, 160 °C, 24 h	90:10	65	[89]
140	Bn	H	3-TBSO-4-MeO-Ph	xylene, 160 °C, 24 h	90:10	58	[89]
141	4-MeO-Ph	4-MeO-Ph	COOEt	o-DCB, 140–180 °C, 16 h	50:50	<60	[90]
142	4-MeO-Ph	4-MeO-Ph	3-CN-4-Cl-Ph-CO	o-DCB, 140 °C, 16 h	50:50	95	[90]
143	4-MeO-Ph	4-MeO-Ph	CH2OH	xylene, 160 °C, 24 h	93:7	97	[90]
144	4-MeO-Ph	3,4,5-tri-MeO-Ph	Me3Si	xylene, 160 °C, 24 h	95:5	100	[91]
145	3,4,5-tri-MeO-Ph	3-NH2-4-MeO-Ph	Me3Si	xylene, 160 °C, 24 h	95:5	91	[91]
146	Ph	CON(Me)OMe	Me3Si	xylene, 160 °C, 24 h	95:5	89	[91]
147	Bn	3-CF3-Ph	Me3Si	xylene, 160 °C, 24 h	95:5	77	[91]
148	3,4,5-tri-MeO-Ph	3-OH-4-MeO-Ph	Me3Si	xylene, 160 °C, 24 h	95:5	82	[91]
149	Ph		Me3Si	xylene, 160 °C, 24 h	95:5	87	[91]
150	4-F-Ph	H	Ph	xylene, 160 °C, 24 h	90:10	100	[91]
151	4-MeO-Ph	H	cyclo-Pr	xylene, 160 °C, 24 h	90:10	91	[91]
152	Ph		cyclo-Pr	xylene, 160 °C, 24 h	95:5	91	[91]
153	Ph	4-Me-Ph	CH2OH	xylene, 160 °C, 24 h	95:5	63	[91]
154	Ph	CON(Me)OMe	cyclo-Pr	xylene, 160 °C, 24 h	95:5	84	[91]
155	Ph	2-Py	Ph	xylene, 160 °C, 24 h	95:5	98	[91]
156	Ph	H	COOEt	o-DCB, 140 °C, 16 h	67:33	59	[92]
156	4-MeO-Ph	H	COOEt	o-DCB, 140 °C, 24 h	67:33	57	[92]

^aIsolated yield of single or both regioisomers. ^bIn a sealed tube. n.d. – not determined.