Metal-free Thiolation of C(sp3)—S Bond Adjacent to an Oxygen Atom†

doi:10.7503/cjcu20150465

Abstract

Abstract:

The formation of C—S bonds is one of the most important transformations in organic chemistry due to the high prevalence of sulfur-containing molecules of biological and pharmaceutical relevance. Cross-dehydrogenative coupling(CDC) is more atom economical and environmentally friendly than traditional cross-coupling reactions. A facile and transition metal-free methodology for construction of C(sp³)—S bond was herein reported. With ditertbutyl peroxide(DTBP) as oxidant and thiophenol as thioetherification regent under 120 ℃, the high atom-efficiency and selective system offered the thiobenzylethers as products in acceptable to good yields. These new compounds were characterized via infrared(IR), nuclear magnetic resonance(NMR), and mass spectrometry(MS). The possible mechanism for the reaction was suggested as followed: benzyl ethers was oxidized by DTBP to generate intermediates A, which further reacted with thiophenol to form desired products. This direct thiolation method is a new protocol for the construction of C—S bonds, which might be very valuable and attractive in sulfur chemistry and radical chemistry.

Key words: Metal free, C—H activation, Thiolation, Thiobenzylether

CLC Number:

O621.3

TrendMD:

YAN Dong, TONG Mengliang. Metal-free Thiolation of C(sp³)—S Bond Adjacent to an Oxygen Atom^†[J]. Chem. J. Chinese Universities, 2016, 37(2): 269.

Figures/Tables 6

Scheme 1 Thioetherification of Isochromans 3a: R=Me, Ar=Ph; 3b: R=Et, Ar=Ph; 3c: R=i-Pr, Ar=Ph; 3d: R=Ph, Ar=Ph; 3e: R=PhCO, Ar=Ph; 3f: R= Me, Ar=4-Me-Ph; 3g: R=Me, Ar=4-OMe-Ph; 3h: R=Me, Ar=4-Cl-Ph; 3i: R= Me, Ar=4-Me-Ph; 3j: R=i-Pr, Ar=Ph; 3k: R=i-Pr, Ar=4-Cl-Ph; 3l: R=—CH2CH2—, Ar=Ph; 3m: R=—CH2CH2—, Ar=4-Cl-Ph

Table 1 Appearance, melting points, HR-MS and IR data of compounds 3a—3m

Compd.	Appearance	m.p./℃	HR-MS, m/z([M]⁺)	IR(KBr), $ν ˙$ /cm^-1
3a	Yellow oil	—	230.0758	2956, 2854, 1645, 1479, 1387, 1022, 745, 698
3b	Yellow solid	67—68	244.0913	2916, 2848, 1490, 1390, 1014, 810, 723
3c	Brown solid	70—72	258.1071	2935, 2860, 1661, 1507, 1379, 1009, 793
3d	Pale yellow oil	—	292.0918	3011, 1597, 1495, 1212, 1019, 798, 694
3e	Brown solid	87—89	320.0866	2930, 1634, 1594, 1392, 1226, 1033, 783
3f	Yellow oil	—	244.0913	3013, 2918, 2843, 1595, 1492, 1238, 1016, 785
3g	Brown solid	72—74	260.0867	2923, 2841, 1593, 1498, 1236, 1012, 831
3h	Yellow solid	77—78	264.0370	2917, 2851, 1478, 1389, 1261, 1101, 1008, 812
3i	Yellow oil	—	272.1223	2941, 2876, 1497, 1354, 1242, 1104, 1011, 806
3j	Pale yellow oil	—	288.1177	2923, 2824, 1596, 1369, 1198, 1016, 822, 697
3k	Yellow oil	—	292.0678	2921, 2837, 1588, 1469, 1382, 1258, 1127, 996, 793
3l	Yellow solid	84—86	242.0759	3012, 2923, 2844, 1596, 1389, 1244, 1012, 803, 698
3m	Yellow solid	81—82	276.0368	3009, 2915, 2832, 1594, 1471, 1254, 1123, 1014, 798

Table 1 Appearance, melting points, HR-MS and IR data of compounds 3a—3m

Compd.	Appearance	m.p./℃	HR-MS, m/z([M]⁺)	IR(KBr), $ν ˙$ /cm^-1
3a	Yellow oil	—	230.0758	2956, 2854, 1645, 1479, 1387, 1022, 745, 698
3b	Yellow solid	67—68	244.0913	2916, 2848, 1490, 1390, 1014, 810, 723
3c	Brown solid	70—72	258.1071	2935, 2860, 1661, 1507, 1379, 1009, 793
3d	Pale yellow oil	—	292.0918	3011, 1597, 1495, 1212, 1019, 798, 694
3e	Brown solid	87—89	320.0866	2930, 1634, 1594, 1392, 1226, 1033, 783
3f	Yellow oil	—	244.0913	3013, 2918, 2843, 1595, 1492, 1238, 1016, 785
3g	Brown solid	72—74	260.0867	2923, 2841, 1593, 1498, 1236, 1012, 831
3h	Yellow solid	77—78	264.0370	2917, 2851, 1478, 1389, 1261, 1101, 1008, 812
3i	Yellow oil	—	272.1223	2941, 2876, 1497, 1354, 1242, 1104, 1011, 806
3j	Pale yellow oil	—	288.1177	2923, 2824, 1596, 1369, 1198, 1016, 822, 697
3k	Yellow oil	—	292.0678	2921, 2837, 1588, 1469, 1382, 1258, 1127, 996, 793
3l	Yellow solid	84—86	242.0759	3012, 2923, 2844, 1596, 1389, 1244, 1012, 803, 698
3m	Yellow solid	81—82	276.0368	3009, 2915, 2832, 1594, 1471, 1254, 1123, 1014, 798

Table 2 1H NMR, 13C NMR data of compounds 3a—3m

Compd.	¹H NMR(400 MHz, CDCl₃), δ	¹³C NMR(100 MHz, CDCl₃), δ
3a	7.17—7.26(m, 10H), 5.67(s, 1H), 3.47(s, 3H)	139.5, 138.0, 134.3, 133.2, 129.5, 128.1, 127.9, 126.4, 90.2, 56.8
3b	7.31(dd, J=4.0, 2.9 Hz, 5H), 7.23(d, J=8.2 Hz, 2H), 7.06(m, 3H), 5.68(s, 1H), 3.42(m, 2H), 1.20(t, J=7.5 Hz, 3H)	139.4, 138.1, 135.1, 133.2, 129.5, 128.1, 128.1, 127.2, 91.3, 58.2, 21.3
3c	7.32—7.30(m, 5H), 7.23(d, J=8.2 Hz, 2H), 7.03(t, J=8.2 Hz, 3H), 5.97(s, 1H), 3.53(m, 1H), 1.29(s, 3H), 1.27(s, 3H)	138.6, 133.7, 131.4, 129.7, 129.3, 129.0, 128.2, 126.3, 85.0, 73.5, 23.9, 23.8
3d	7.34—7.28(m, 5H), 7.24—7.20(m, 5H), 7.11—7.08(t, J=8.2 Hz, 2H), 6.93—6.85(m, 3H), 6.07(s, 1H)	146.5, 139.0, 134.5, 132.5, 132.3, 130.8, 130.7, 129.4, 129.3, 128.5, 127.6, 125.4, 119.8, 89.2
3e	7.97(d, J=6.1 Hz, 2H), 7.47(t, J=7.4 Hz, 1H), 7.40(t, J=7.4 Hz, 2H), 7.35—7.15(m, 10H), 7.09(t, J=7.4 Hz, 1H)	164.2, 138.9, 133.8, 133.3, 131.4, 131.3, 130.5, 129.8, 129.7, 129.7, 129.6, 129.4, 129.3, 128.8, 128.7, 128.6, 128.4, 125.9, 125.8, 85.3
3f	7.48(d, J=7.8 Hz, 2H), 7.40—7.30(m, 1H), 7.26—7.00(m, 5H), 6.45(s, 1H), 4.55—4.52(m, 1H), 3.98(dd, J=11.4, 6.3 Hz, 1H), 3.25—3.05(m, 1H), 2.65—2.63(m, 1H), 2.28(s, 3H)	137.4, 134.0, 133.9, 132.2, 132.1, 129.8, 128.9, 127.7, 127.2, 126.1, 86.4, 77.4, 77.1, 76.9, 58.2, 27.9, 21.2
3g	7.31—7.25(m, 7H), 6.84(d, J=8.2 Hz, 2H), 5.68(s, 1H), 3.82(s, 3H), 3.42(s, 3H)	141.3, 139.0, 134.3, 133.2, 129.4, 128.2, 127.6, 125.2, 90.2, 58.2, 56.8
3h	7.30—7.29(d, J=8.3 Hz, 4H), 7.25—7.22(m, 5H), 5.80(s, 1H), 3.82(s, 3H), 3.38(s, 3H)	138.3, 136.0, 133.5, 132.8, 132.0, 129.3, 128.2, 127.6, 126.9, 89.2, 55.9
3i	7.31—7.22(m, 7H), 7.08(d, J=8.2 Hz, 2H), 5.68(s, 1H), 3.51(m, 2H), 1.27(s, 3H), 1.26(s, 6H)	139.6, 138.9, 133.3, 131.2, 130.8, 129.1, 128.7, 126.4, 87.9, 78.2, 23.7, 21.2
3j	7.32—7.28(m, 6H), 7.24(t, J=7.5 Hz, 1H), 6.98(d, J=8.2 Hz, 2H), 5.68(s, 1H), 3.68(s, 1H), 3.47(m, 1H), 1.24(s, 3H), 1.22(s, 6H)	142.8, 138.9, 133.3, 131.2, 130.8, 128.7, 126.4, 115.6, 87.9, 75.2, 56.0, 22.7, 21.2
3k	7.32—7.28(m, 6H), 7.28—7.21(m, 3H), 5.68(s, 1H), 3.47(m, 1H), 1.24(s, 3H), 1.22(s, 6H)	138.9, 135.5, 133.6, 132.2, 129.9, 128.9, 128.2, 126.4, 87.9, 75.2, 21.2
3l	7.43—7.31(m, 5H), 7.24—7.19(m, 4H), 6.49(s, 1H), 4.55—4.53(m, 2H), 3.20—3.09(m, 1H), 2.72(dd, J=16.5, 2.4 Hz, 1H)	136.6, 132.9, 132.5, 132.3, 132.2, 128.1, 127.9, 126.9, 126.1, 125.2, 85.1, 57.4, 25.9
3m	7.62(d, J=7.8 Hz, 2H), 7.41—7.32(m, 1H), 7.26—7.00(m, 5H), 6.45(s, 1H), 4.55(m, 1H), 3.98(dd, J=11.4, 6.3 Hz, 1H), 3.25—3.05(m, 1H), 2.65(dd, J=16.5, 2.9 Hz, 1H), 2.28(s, 3H)	138.4, 136.0, 133.5, 132.7, 132.0, 129.3, 128.2, 127.6, 126.9, 126.1, 125.2, 85.1, 57.5, 25.8

Table 2 1H NMR, 13C NMR data of compounds 3a—3m

Compd.	¹H NMR(400 MHz, CDCl₃), δ	¹³C NMR(100 MHz, CDCl₃), δ
3a	7.17—7.26(m, 10H), 5.67(s, 1H), 3.47(s, 3H)	139.5, 138.0, 134.3, 133.2, 129.5, 128.1, 127.9, 126.4, 90.2, 56.8
3b	7.31(dd, J=4.0, 2.9 Hz, 5H), 7.23(d, J=8.2 Hz, 2H), 7.06(m, 3H), 5.68(s, 1H), 3.42(m, 2H), 1.20(t, J=7.5 Hz, 3H)	139.4, 138.1, 135.1, 133.2, 129.5, 128.1, 128.1, 127.2, 91.3, 58.2, 21.3
3c	7.32—7.30(m, 5H), 7.23(d, J=8.2 Hz, 2H), 7.03(t, J=8.2 Hz, 3H), 5.97(s, 1H), 3.53(m, 1H), 1.29(s, 3H), 1.27(s, 3H)	138.6, 133.7, 131.4, 129.7, 129.3, 129.0, 128.2, 126.3, 85.0, 73.5, 23.9, 23.8
3d	7.34—7.28(m, 5H), 7.24—7.20(m, 5H), 7.11—7.08(t, J=8.2 Hz, 2H), 6.93—6.85(m, 3H), 6.07(s, 1H)	146.5, 139.0, 134.5, 132.5, 132.3, 130.8, 130.7, 129.4, 129.3, 128.5, 127.6, 125.4, 119.8, 89.2
3e	7.97(d, J=6.1 Hz, 2H), 7.47(t, J=7.4 Hz, 1H), 7.40(t, J=7.4 Hz, 2H), 7.35—7.15(m, 10H), 7.09(t, J=7.4 Hz, 1H)	164.2, 138.9, 133.8, 133.3, 131.4, 131.3, 130.5, 129.8, 129.7, 129.7, 129.6, 129.4, 129.3, 128.8, 128.7, 128.6, 128.4, 125.9, 125.8, 85.3
3f	7.48(d, J=7.8 Hz, 2H), 7.40—7.30(m, 1H), 7.26—7.00(m, 5H), 6.45(s, 1H), 4.55—4.52(m, 1H), 3.98(dd, J=11.4, 6.3 Hz, 1H), 3.25—3.05(m, 1H), 2.65—2.63(m, 1H), 2.28(s, 3H)	137.4, 134.0, 133.9, 132.2, 132.1, 129.8, 128.9, 127.7, 127.2, 126.1, 86.4, 77.4, 77.1, 76.9, 58.2, 27.9, 21.2
3g	7.31—7.25(m, 7H), 6.84(d, J=8.2 Hz, 2H), 5.68(s, 1H), 3.82(s, 3H), 3.42(s, 3H)	141.3, 139.0, 134.3, 133.2, 129.4, 128.2, 127.6, 125.2, 90.2, 58.2, 56.8
3h	7.30—7.29(d, J=8.3 Hz, 4H), 7.25—7.22(m, 5H), 5.80(s, 1H), 3.82(s, 3H), 3.38(s, 3H)	138.3, 136.0, 133.5, 132.8, 132.0, 129.3, 128.2, 127.6, 126.9, 89.2, 55.9
3i	7.31—7.22(m, 7H), 7.08(d, J=8.2 Hz, 2H), 5.68(s, 1H), 3.51(m, 2H), 1.27(s, 3H), 1.26(s, 6H)	139.6, 138.9, 133.3, 131.2, 130.8, 129.1, 128.7, 126.4, 87.9, 78.2, 23.7, 21.2
3j	7.32—7.28(m, 6H), 7.24(t, J=7.5 Hz, 1H), 6.98(d, J=8.2 Hz, 2H), 5.68(s, 1H), 3.68(s, 1H), 3.47(m, 1H), 1.24(s, 3H), 1.22(s, 6H)	142.8, 138.9, 133.3, 131.2, 130.8, 128.7, 126.4, 115.6, 87.9, 75.2, 56.0, 22.7, 21.2
3k	7.32—7.28(m, 6H), 7.28—7.21(m, 3H), 5.68(s, 1H), 3.47(m, 1H), 1.24(s, 3H), 1.22(s, 6H)	138.9, 135.5, 133.6, 132.2, 129.9, 128.9, 128.2, 126.4, 87.9, 75.2, 21.2
3l	7.43—7.31(m, 5H), 7.24—7.19(m, 4H), 6.49(s, 1H), 4.55—4.53(m, 2H), 3.20—3.09(m, 1H), 2.72(dd, J=16.5, 2.4 Hz, 1H)	136.6, 132.9, 132.5, 132.3, 132.2, 128.1, 127.9, 126.9, 126.1, 125.2, 85.1, 57.4, 25.9
3m	7.62(d, J=7.8 Hz, 2H), 7.41—7.32(m, 1H), 7.26—7.00(m, 5H), 6.45(s, 1H), 4.55(m, 1H), 3.98(dd, J=11.4, 6.3 Hz, 1H), 3.25—3.05(m, 1H), 2.65(dd, J=16.5, 2.9 Hz, 1H), 2.28(s, 3H)	138.4, 136.0, 133.5, 132.7, 132.0, 129.3, 128.2, 127.6, 126.9, 126.1, 125.2, 85.1, 57.5, 25.8

Table 3 Optimization of the reactions between thiophenol and benzyl ethera

Entry	Oxidant	n(Oxidant)/mmol	T/℃	Solvent	Yield^b(%)
1	DTBP	4.0	120	Dioxane	39
2	K₂S₂O₈	4.0	120	Dioxane
3	TBHP	4.0	120	Dioxane	20
4	DDQ	4.0	120	Dioxane	12
5	BPO	4.0	120	Dioxane	Trace
6	DTBP	3.0	120	Dioxane	44
7	DTBP	2.0	120	Dioxane	53
8	DTBP	1.5	120	Dioxane	80
9	DTBP	1.0	120	Dioxane	32
10	DTBP	1.5	100	Dioxane	58
11	DTBP	1.5	140	Dioxane	67
12	DTBP	1.5	120	Benzene	69
13	DTBP	1.5	120	PhCl	56
14	DTBP	1.5	120	Toluene	13

Table 4 Scope of the reactiona

Entry	Yield(%)^b	Entry	Yield(%)^b
1	79	7	82
2	78	8	74
3	82	9	86
4	79	10	81
5	77	11	76
6	80	12	76

Scheme 2 Proposed reaction mechanism

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Metal-free Thiolation of C(sp³)—S Bond Adjacent to an Oxygen Atom^†

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