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Synlett 2008(8): 1165-1170  
DOI: 10.1055/s-2008-1072725
LETTER
© Georg Thieme Verlag Stuttgart · New York

Regioselective Markovnikov Hydrochalcogenation of Terminal Alkynes with Indium(III) Benzenechalcogenolates

Clovis Peppe*, Liérson Borges de Castro, Melina de Azevedo Mello, Olga Soares do Rego Barros
Departamento de Química, Universidade Federal de Santa Maria-UFSM, Campus UFSM, Santa Maria, RS - 97105-900, Brazil
Fax: +55(55)32208031; e-Mail: peppe@quimica.ufsm.br;
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Publication History

Received 18 June 2007
Publication Date:
16 April 2008 (online)

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Abstract

Indium(III) benzenechalcogenolates (chalcogen = sulfur and selenium) promote the rigorous Markovnikov hydrochalcogenation of terminal alkynes. The generality and limitations of the reaction with aminoalkynes leading to allylic amines bearing vinylic chalcogenide substituents are discussed.

Key words

indium(III) benzenechalcogenolates - aminoalkynes - hydrochalcogenation - regioselective Markovnikov addition.

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General Procedure for the Markovnikov Hydrochalcogenation of the Aminoalkynes
A Schlenk tube equipped with a reflux condenser, under N2 atmosphere, was charged with DCE (2 mL), i-PrOH (0.1 mL), aminoalkyne 5 (1 mmol), and In(EPh)3 (1 mmol). The mixture was heated, under reflux, for 6 h. At the end of this period, the reaction was quenched with H2O (10 mL), the organics extracted with CH2Cl2 (2 × 15 mL). The extract was dried (Na2SO4) and evaporated to dryness under vacuum. The oily residue was purified by column chromatography (SiO2, hexanes-EtOAc) to produce the adducts 6 and 6′ as heavy oils and in yields given in Table [2] .
Spectroscopic Data for Compounds 6
2-(Phenylthio)prop-2-en-1-amine (6a):19 1H NMR (CDCl3): δ = 7.54-7.17 (m, 5 H), 5.31 (t, J = 1.2 Hz, 1 H), 4.98 (s, 1 H), 3.28 (s, 2 H), 1.82 (s, 2 H). 13C NMR (CDCl3): δ = 136.96, 132.51, 129.08, 128.60, 127.65, 113.59, 46.87.
2-(Phenylseleno)prop-2-en-1-amine (6′a): 1H NMR (CDCl3): δ = 7.43 (m, 2 H), 7.18 (m, 3 H), 5.61 (s, 1 H), 5.19 (s, 1 H), 3.30 (s, 2 H), 1.70 (s, 2 H). 13C NMR (CDCl3): δ = 144.50, 133.89, 128.98, 128.15, 127.47, 116.45, 48.37.
4-Methyl-N-(2-(phenylthio)allyl)benzenesulfonamide (6b): 1H NMR (CDCl3): δ = 7.62 (m, 2 H), 7.19 (m, 7 H), 5.35 (s, 1 H), 5.03 (s, 1 H), 3.56 (s, 2 H), 2.31 (s, 3 H). Fast decomposition in CDCl3 solution prevented the recording of a satisfactory 13C NMR spectrum.
N-[2,2-Bis(phenylthio)propyl]-4-methylbenzenesulfon-
amide (secondary product): 1H NMR (CDCl3): δ = 7.71 (m, 2 H), 7.45 (m, 4 H), 7.37 (m, 2 H), 7.30 (m, 6 H), 5.13 (t, J = 6.0 Hz, 1 H), 2.98 (d, J = 6.0 Hz, 2 H), 2.36 (s, 3 H), 1.19 (s, 3 H). 13C NMR (CDCl3): δ = 143.45, 136.91, 136.50, 129.85, 129.68, 129.60, 128.80, 127.04, 61.41, 50.58, 25.64, 21.47.
4-Methyl-N-[2-(phenylseleno)allyl]benzenesulfonamide (6′b): 1H NMR (CDCl3): δ = 7.61 (m, 2 H), 7.32 (m, 2 H), 7.18 (m, 5 H), 5.67 (s, 1 H), 5.25 (s, 1 H), 3.60 (s, 2 H), 2.32 (s, 3 H). 13C NMR (CDCl3): δ = 143.32, 136.78, 136.71, 133.85, 129.50, 129.27, 127.86, 127.62, 127.02, 120.61, 48.69, 21.39.
N-Methyl-2 (phenylthio)prop-2-en-1-amine (6c): 1H NMR (CDCl3): δ = 7.38-7.18 (m, 5 H), 5.26 (s, 1 H), 4.96 (s, 1 H), 3.23 (s, 2 H), 2.29 (s, 3 H), 1.64 (s, 1 H). 13C NMR (CDCl3): δ = 143.72, 132.88, 132.60, 129.06, 127.73, 114.68, 55.84, 34.92.
N-Methyl-2 (phenylseleno)prop-2-en-1-amine (6′c) 1H NMR (CDCl3): δ = 7.47 (m, 2 H), 7.22 (m, 3 H), 5.60 (s, 1 H), 5.14 (s, 1 H), 3.29 (s, 2 H), 2.29 (s, 3 H), 1.83 (s, 1 H). 13C NMR (CDCl3): δ = 141.59, 134.62, 129.20, 128.35, 127.81, 117.71, 57.40, 34.92.
N,N-Diethyl-2 (phenylthio)prop-2-en-1-amine (6d):20 1H NMR (CDCl3): δ = 7.43-7.20 (m, 5 H), 5.26 (s, 1 H), 4.73 (s, 1 H), 3.14 (s, 2 H), 2.50 (q, J = 7.1 Hz, 4 H), 0.95 (t, J = 7.1 Hz, 6 H). 13C NMR (CDCl3): δ = 145.24, 133.81, 133.05, 129.03, 127.86, 112.44, 58.33, 46.61, 11.54. N,N-Diethyl-2 (phenylseleno)prop-2-en-1-amine (6′d): 1H NMR (CDCl3): δ = 7.53 (m, 2 H), 7.23 (m, 3 H), 5.55 (s, 1 H), 4.79 (s, 1 H), 3.24 (s, 2 H), 2.50 (q, J = 7.1 Hz, 4 H), 0,97 (t, J = 7.1 Hz, 6 H). 13C NMR (CDCl3): δ = 144.57, 135.85, 131.49, 129.11, 127.89, 113.83, 59.91, 46.45, 11.60.
4-[2-(Phenylthio)allyl]morpholine (6e): 1H NMR (CDCl3): δ = 7.39 (m, 2 H), 7.25 (m, 3 H), 5.20 (s, 1 H), 4.72 (s, 1 H), 3.65 (m, 4 H), 3.04 (s, 2 H), 2.37 (m, 4 H). 13C NMR (CDCl3): δ = 143.36, 134.15, 132.48, 129.06, 128.13, 112.84, 66.89, 63.86, 53.14.
4-[2-(Phenylseleno)allyl]morpholine (6′e): 1H NMR (CDCl3): δ = 7.52 (m, 2 H), 7.23 (m, 3 H), 5.51 (s, 1 H), 4.80 (s, 1 H), 3.64 (m, 4 H), 3.14 (s, 2 H), 2.38 (m, 4 H). 13C NMR (CDCl3): δ = 142.42, 136.03, 129.11, 128.40, 128.07, 114.44, 66.93, 65.30, 53.13.
1-[2-(Phenylthio)allyl)]piperidine (6f): 1H NMR (CDCl3): δ = 7.39 (m, 2 H), 7.24 (m, 3 H), 5.23 (s, 1 H), 4.74 (s, 1 H), 3.02 (s, 2 H), 2.33 (m, 4 H), 1.53 (m, 4 H), 1.36 (m, 2 H). 13C NMR (CDCl3): δ = 143.77, 133.96, 132.88, 129.06, 127.99, 112.90, 64.10, 54.18, 25.77, 24.25.
1-[2-(Phenylseleno)allyl)]piperidine (6′f): 1H NMR (CDCl3): δ = 7.53 (m, 2 H), 7.23 (m, 3 H), 5.51 (s, 1 H), 4.80 (s, 1 H), 3.11 (s, 2 H), 2.34 (m, 4 H), 1.53 (m, 4 H), 1.37 (m, 2 H). 13C NMR (CDCl3): δ = 143.23, 135.96, 129.11, 128.87, 127.96, 114.10, 65.54, 54.20, 25.83, 24.27.
4-[2-(Phenylthio)oct-1-en-3-yl]morpholine (6g): 1H NMR (CDCl3): δ = 7.40 (m, 2 H), 7.25 (m, 3 H), 5.00 (s, 1 H), 4.46 (s, 1 H), 3.65 (t, J = 4.6 Hz, 4 H), 2.80 (dd, J = 7.8, 6.1 Hz, 1 H), 2.49 (m, 4 H), 1.62 (m, 2 H), 1.24 (m, 6 H), 0.82 (t, J = 6.5 Hz, 3 H). 13C NMR (CDCl3): δ = 147.61, 136.62, 129.18, 128.58, 128.14, 113.58, 72.22, 67.18, 50.85, 31.85, 29.67, 26.32, 22.52, 14.01.
4-[2-(Phenylseleno)oct-1-en-3-yl]morpholine (6′g): 1H NMR (CDCl3): δ = 7.51 (m, 2 H), 7.25 (m, 3 H), 5.41 (s, 1 H), 4.68 (s, 1 H), 3.65 (t, J = 4.5 Hz, 4 H), 2.79 (dd, J = 8.2, 5.6 Hz, 1 H), 2.50 (m, 4 H), 1.56 (m, 2 H), 1.23 (m, 6 H), 0.82 (t, J = 6.2 Hz, 3 H). 13C NMR (CDCl3): δ = 147.62, 135.18, 132.07, 129.17, 128.41, 110.38, 71.49, 67.15, 50.85, 31.79, 29.87, 26.03, 22.50, 13.99.
4-[4-(Phenylthio)pent-4-enyl]morpholine (6j): 1H NMR (CDCl3): δ = 7.37-7.20 (m, 5 H), 5.09 (s, 1 H), 4.83 (s, 1 H), 3.63 (m, 4 H), 2.36 (m, 4 H), 2.23 (m, 4 H), 1.67 (quint, J = 7.9 Hz, 2 H). 13C NMR (CDCl3): δ = 145.26, 133.07, 129.09, 128.54, 127.77, 113.29, 66.71, 57.86, 53.49, 34.10, 24.92.
4-[4-(Phenylseleno)pent-4-enyl]morpholine (6′j): 1H NMR (CDCl3): δ = 7.45 (m, 2 H), 7.23 (m, 3 H), 5.43 (s, 1 H), 5.08 (s, 1 H), 3.64 (m, 4 H), 2.37 (m, 4 H), 2.28 (t, J = 7.5 Hz, 2 H), 2.23 (t, J = 7.5 Hz, 2 H), 1,67 (quint, J = 7.5 Hz, 2 H). 13C NMR (CDCl3): δ = 142.29, 134.54, 129.20, 128.65, 127.79, 117.19, 66.36, 57.64, 53.27, 35.76, 24.83.

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We have searched for the reasons leading to this failure. From the reaction involving homopropargylamine 5i and In(SePh)3, we have isolated after 24 h of continuous reflux 1,2-bis(phenylseleno)ethane (PhSeCH2CH2SePh) in 62% of yield based on 5i. 1H NMR (CDCl3): δ = 7.35 (m, 4 H), 7.17 (m, 6 H), 3.05 (s, 4 H). 13C NMR (CDCl3): δ = 133.04, 131.45, 129.14, 127.21, 27.16.14 Bis(phenylseleno)ethane was similarly prepared by heating In(SePh)3, Et3N in DCE in 40% of yield. These facts strongly suggest parallel reactions between aminoalkynes 5i and 5j with DCE to form quaternary ammonium derivatives that inhibit or reduce the efficiency of the hydrochalcogenation reactions.

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4-[3,3-Dideuterio-2-(phenylseleno)allyl]morpholine was prepared, in 83% of yield, according to the general method described above using D2O as the deuterium source: 1H NMR (CDCl3): δ = 7.52 (m, 2 H), 7.23 (m, 3 H), 5.51 (s, 0.2 H), 4.80 (s, 0.2 H), 3.64 (m, 4 H), 3.14 (s, 2 H), 2.38 (m, 4 H).

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(E)-4[2,3-Bis(phenylseleno)allyl]morpholine (7′e) was prepared in 53% of yield together with 6′e (24%) from aminoalkyne 5e (1 mmol), In(SePh)3 (1 mmol), and diphenyl diselenide (2 mmol) in anhyd DCE (4 mL) using the general procedure described in ref. 12.
Spectroscopic Data for 7′e
1H NMR (CDCl3): δ = 7.48 (m, 2 H), 7.33 (m, 2 H), 7.22 (m, 3 H), 7.18 (m, 3 H), 6.67 (s, 1 H), 3.67 (m, 4 H), 3.22 (s, 2 H), 2.42 (m, 4 H). 13C NMR (CDCl3): δ = 134.33, 133.04, 131.55, 129.53, 129.28, 129.21, 129.08, 127.84, 126.95, 123.81, 66.80, 63.26, 52.97; 2D-NOE: no effect involving the singlet at δ = 6.67 ppm as required by the E-stereo-
isomer.

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Spectroscopic Data for the Products of Hydrochalcogenation of n -Decyne with Indium(III) Benzenechalcogenolates
2-Phenylselenodec-1-ene (2′):7 1H NMR (CDCl3): δ = 7.48 (m, 2 H), 7.22 (m, 3 H), 5.43 (s, 1 H), 5.04 (s, 1 H), 2.21 (t, J = 7.3 Hz, 2 H), 1.47 (quint, J = 7.3 Hz, 2 H), 1.20 (br s, 10 H), 0.82 (t, J = 6.8 Hz, 3 H). 13C NMR (CDCl3): δ = 143.5, 134.67, 129.13, 129.04, 127.65, 116.07, 38.32, 31.83, 29.32, 29.19, 28.81, 28.67, 22.64, 14.09.
(Z)- + (E)-2-Phenylselenodec-2-ene (8′; isolated as an unassigned 3:2 mixture of isomers): 1H NMR (CDCl3): δ = 7.38 (m, 2 H), 7.16 (m, 3 H), 5.89 (t, J = 7.3 Hz, 0.4 H), 5.71 (t, J = 7.1 Hz, 0.6 H), 2.18 (q, J = 7.1 Hz, 1.2 H), 2.03 (q, J = 7.3 Hz, 0.8 H), 1.92 (s, 3 H), 1.32 (quint, J = 7.3 Hz, 2 H), 1.21 (m, 8 H), 0.81 (t, J = 7.3 Hz, 1.2 H), 0.80 (t, J = 7.3 Hz, 1.8 H).
(Z)- + (E)-2-Phenylthiodec-2-ene (8, isolated as an unassigned 1:1 mixture of isomers): 1H NMR (CDCl3): δ = 7.34 (m, 5 H), 5.95 (tq, J = 7.3 Hz, 1.2 Hz, 0.5 H), 5.89 (tq, J = 7.3 Hz, 1.2 Hz, 0.5 H), 2.38 (q, J = 7.2 Hz, 1 H), 2.19 (q, J = 7.3 Hz, 1 H), 1.97 (d, J = 1.2 Hz, 1.5 H), 1.94 (d, J = 1.2 Hz, 1.5 H), 1.47 (m, 2 H), 1.35 (m, 8 H), 0.95 (m, 3 H).