Regio- and Stereoselective Copper-Catalyzed Addition of Aromatic and Aliphatic Thiols to Terminal and Internal Nonactivated Alkynes

Abstract

The CuI-catalyzed regio- and stereoselective hydrothio­lation of terminal and internal alkynes affords (Z)-β-alkenylsulfides. The following isomerization of the Z-isomers into E-isomers catalyzed by CuI is described.

hydrothiolation - alkynes - copper catalyst - stereoselective anti-Markovnikov addition - isomerization

References and Notes

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<A NAME="RB60311ST-24">24</A>

The products 3a, [¹²r] [¹6f] [¹9] 3c, [²0] 3d, [¹²r] [²¹] 3b, [¹5l] [²²a] [b] 3e, [¹²q] [¹4c] [²³a] [b] 3f, [²³a] 3g,h, [¹8] 3i, [¹²i] [¹5b] [l] [¹6b] [¹7] 3k, [¹5b] [³¹] were identified according to published data. The Z/E isomeric ratio for 3i and 3k was determined by ^¹H NMR and ^¹³C NMR spectroscopy.

<A NAME="RB60311ST-25">25</A>

Typical Experimental Procedure for the CuI-Catalyzed Hydrothiolation of the Alkynes To a mixture of phenylacetylene (1a, 0.102 g, 1 mmol), CuI (0.006 g, 3 mol%) in DMF (0.5 mL) was added HexSH (2c, 0.118 g, 1 mmol) under an argon atmosphere, the mixture was stirred at 80 ˚C for 2 h and then evaporated under vacuum. The resulting oil was diluted with CHCl₃ and filtered. The filtrate was concentrated and purified by column chromatography on silica gel (EtOAc-hexane, 5:95) to afford hexyl-(2-styryl)sulfide (3f, [²³a] 0.198 g, 90%; Z/E = 15:1 by NMR) as a colorless oil. ^¹H NMR (400 MHz, CDCl₃): δ (Z-isomer) = 7.46-7.15 (m, 5 H, Ph), 6,39 (d, ^³ J _HH = 10.5 Hz, 1 H, PhCH=), 6.20 (d, ^³ J _HH = 10.5 Hz, 1 H, =CHS), 2.72 (t, ^³ J _HH = 7.4 Hz, 2 H, CH₂S), 1.65 (m, 2 H), 1.38 (m, 2 H), 1.28 (m, 4 H), 0.87 (t, 3 H, CH₃); δ (E-isomer) = 7.34-7.16 (m, 5 H, Ph), 6.72 (d, ^³ J _HH = 16.0 Hz, 1 H, PhCH=), 6.46 (d, ^³ J _HH = 16.0 Hz, 1 H, =CHS), 2.79 (t, ^³ J _HH = 7.4 Hz, 2 H, CH₂S), 1.69 (m, 2 H), 1.43 (m, 2 H), 1.31 (m, 4 H), 0.90 (t, 3 H, CH₃). ^¹³C NMR (100.6 MHz, CDCl₃): δ (Z-isomer) = 136.94, 128.45, 128.02, 127.57, 126.55, 125.59, 35.80, 31.27, 30.10, 28.15, 22.43, 13.93; δ (E-isomer) = 136.98, 128.48, 128.05, 127.60, 126.35, 125.05, 32.52, 31,25, 29.23, 28.36, 22.41, 13.96.

<A NAME="RB60311ST-26">26</A>

( E )- N , N -Dimethyl-3-(phenylthio)-2-propenylamine (3c) [²0] ^¹H NMR (400 MHz, CDCl₃): δ = 7.22-7.50 (m, Ph), 6.39 (dt, ^³ J _HH = 16.0 Hz, J _HH = 1.4 Hz, 1 H, =CHS), 5.87 (dt, ^³ J _HH = 16.0 Hz, J _HH = 1.4 Hz, 1 H, =CHC), 3.23 (d, J _HH = 8.0 Hz, 2 H, CH₂N), 2.36 (s, 6 H, CH₃N). ^¹³C NMR (100.6 MHz, CDCl₃): δ = 135.57, 128.93, 128.84, 128.11, 126.55, 126.36, 57.10, 44.91. Anal. Calcd for C₁₁H₁₅NS: C, 68.37; H, 7.81; N, 7.25. Found: C, 68.25; H, 8.00; N, 7.38.

<A NAME="RB60311ST-27">27</A>

3-(Phenylthio)prop-2-en-1-ol (3d, E/Z  = 5:1) [¹²r] [²¹]
E -Isomer
^¹H NMR (400 MHz, CDCl₃): δ = 7.20-7.49 (m, 5 H, Ph), 6.43 (dt, ^³ J _HH = 14.0 Hz, J _HH = 1.4 Hz, 1 H, =CHS), 5.93 (dt, ^³ J _HH = 1.4 Hz, 1 H, =CHC), 4.16 (d, ^² J _HH = 7.15 Hz, 2 H, H₂CO), 2.15 (br s, 1 H, OH). ^¹³C NMR (100.6 MHz, CDCl₃): δ = 132.99, 130.93, 129.96, 128.98, 127.36, 127.05, 63.07.
Z -Isomer
^¹H NMR (400 MHz, CDCl₃): δ = 7.20-7.49 (m, 5 H, Ph), 6.33 (dt, ^³ J _HH = 8.0 Hz, J _HH = 1.2 Hz, 1 H, =CHS), 5.90-5.96 (m, 1 H, =CHC), 4.34 (d, ^² J _HH = 7.12 Hz, 2 H, H₂CO), 2.13 (br s, 1 H, OH). ^¹³C NMR (100.6 MHz, CDCl₃): δ = 136.88, 129.58, 129.04, 128.98, 127.36, 126.91, 59.65. Anal. Calcd. for C₉H₁₀OS: C, 65.06; H, 6.02. Found: C, 65.26; H, 6.19.

<A NAME="RB60311ST-28">28</A>

( Z )-3-(2-Styrylthio)propanethiol (3g) [¹8]

^¹H NMR (400 MHz, CDCI₃): δ = 7.19-7.48 (m 5 H, Ph), 6.44 (dd, ^³ J _HH = 10.8 Hz, 1 H, =CHPh), 6.17 (dd, ^³ J _HH = 10.8 Hz, 1 H, =CHS), 2.84-2.93 (m, 2 H, =CSCH₂), 2.57-2.63 (m, 2 H, H₂CSH), 1.82-1.97 (m, 2 H, CCH₂C), 1.34 (t, ^³ J _HH = 7.0 Hz, 1 H, SH). ^¹³C NMR (100.6 MHz, CDCI₃): δ = 137.20, 129.16, 128.66, 128.25, 126.91 126.74, 41.61, 30.60, 25.64.

<A NAME="RB60311ST-29">29</A>

2-Benzyl-1,3-dithiane (3h) [¹7]

^¹H NMR (400 MHz, CDCI₃): δ = 7.25-7.31 (m, 5 H, Ph), 4.25 (t, 1 H, SCH₂S), 2.94 (d, 2 H, H₂CPh), 2.73 (m, 4 H, SCH₂C), 2.05 (m, 1 H), 1.88 (m, 1 H). ^¹³C NMR (100.6 MHz, CDCI₃): δ = 137.20, 129.16, 128.25, 126.91, 48.82, 41.59, 30.60, 25.60.

<A NAME="RB60311ST-30">30</A>

1-Phenyl-2-(phenylthio)propene (3i, [¹²i] [¹5b] [l] [¹6b] [¹8] Z / E  = 5:1)
^¹H NMR (400 MHz, CDCl₃): δ = 7.15-7.55 (21 H, m), 6.69 (1 H, s, Z form), 2.12 (3 H, s, E form, 0.17), 2.01 (3 H, s, Z form, 0.83). ^¹³C NMR (100.6 MHz, CDCl₃): δ (Z) = 136.72, 133.50, 131.98, 131.57, 130.79, 128.98, 128.82, 127.96, 127.12, 126.91, 25.55; δ (E) = 137.04, 133.83, 131.96, 131.41, 130.69, 129.03, 128.62, 128.21, 127.33, 126.69, 19.49.

<A NAME="RB60311ST-31">31</A>

( Z )-1,2-Diphenyl-1-(phenylthio)ethene (3k) [¹5b]

^¹H NMR (400 MHz, CDCl₃): δ = 7.72 (1 H, d, J = 7.6 Hz), 7.62 (1 H, d, J = 7.8 Hz), 6.92-7.52 (13 H, m), 6.79 (1 H, s). ^¹³C NMR (100.6 MHz, CDCl₃): δ = 140.83, 137.86, 136.64, 135.64, 134.56, 132.25, 129.74, 129.44, 129.00, 128.58, 128.10, 127.95, 127.36, 125.73.

<A NAME="RB60311ST-32">32</A>

Typical Procedure for the Thermal and CuI-Catalyzed Z - to E -Isomerization of Alkenyl Sulfides In each of two Schlenk tubes under argon atmosphere were placed phenyl-(2-styryl)sulfide (Z/E = 2.4:1, 0.106 g, 0.5 mmol). In one of the Schlenk tubes were added thiophenol (2a, 0.055 g, 0.05 mmol), and CuI (0.006 g, 3 mol%). Both tubes were heated at 85 ˚C. The changes of the Z/E ratio was inspected by ^¹H NMR spectroscopy. After 4 h without PhSH and CuI the ratio was Z/E = 1.8:1, with CuI and thiol only 100% E-isomer 3a was observed (Table  [³] , entry 1).