Phenylselenofluorination of Alkenes and Alkynes Promoted by Difluoroiodotoluene and Diphenyldiselenide

Abstract

The oxidation of diphenyldiselenide with 4-iodotoluene difluoride (DFIT) in dichloromethane produces in situ an efficient phenylselenofluorinating agent of alkenes and internal alkynes.

Key words

alkenes - alkynes - hypervalent iodine(III) difluoride - diphenyldiselenide - oxidation

References

• 1a Tingoli M. Tiecco M. Testaferri L. Temperini A. Synth. Commun.  1998,  28:  1769 
• 1b De Corso AR. Panunzi B. Tingoli M. Tetrahedron Lett.  2001,  42:  7245 
• 2 Panunzi B. Rotiroti L. Tingoli M. Tetrahedron Lett.  2003,  44:  8753 
• 3 Motherwell WB. Wilkinson JA. Synlett  1991,  191 
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• 6 Greaney MF. Motherwell WB. Tocher DA. J. Chem Soc., Perkin Trans. 1  2002,  2809 
• 7 Edmunds JJ. Greaney MF. Motherwell WB. Steed JW. J. Chem Soc., Perkin Trans. 1  2002,  2816 
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• 8b Lermontov SA. Zavorin SI. Pushin AN. Chekhlov AN. Zefirov NS. Stang PJ. Tetrahedron Lett.  1993,  34:  703 
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• 12a Unfortunately spectroscopic properties of compound 6a were not reported in ref.. Nevertheless, some analogs of our compounds 6a and 7a (Table 1) were recently described by: Cumpstey I. Fairbanks AJ. Redgrave AJ. Org. Lett.  2001,  3:  2371 
• 12b

  The first one is the 2-O-acetyl-3,4,6-tri-O-benzyl-β-d-glucopyranosyl fluoride that shows in its ¹H NMR spectrum a J _1,2 between H-1 and H-2 of 6.1 Hz, while the second one named 2-O-acetyl-3,4,6-tri-O-benzyl-α-d-mannopyranosyl fluoride shows a J _1,2 of 1.9 Hz beween H-1 nd H-2. This last value of J _1,2 is consistent with our data.

• 13 Khrimian AP. De Milo AB. Waters RM. Liquido NJ. Nicholson JM. J. Org. Chem.  1994,  59:  8034 
• 14 Tingoli M. Tiecco M. Testaferri L. Temperini A. Tetrahedron  1995,  51:  4691 

15

A Typical Procedure for the Phenylselenofluorination Reaction Promoted by DFIT and PhSeSePh in CH ₂ Cl ₂ . Diphenyldiselenide (0.16 mmol) was dissolved in CH₂Cl₂ (3 mL) in a 20 mL polyethylene erlenmeyer flask and DFIT (0.40 mmol) was added under stirring in Ar atmosphere. The initially yellow solution turns to a red-brown color in a few minutes. After 15 min a CH₂Cl₂ solution (3 mL) of the starting material (0.30 mmol) was added slowly. The color of the solution disappeared in a few minutes and all the reactions described on alkenes were completed in less than 90 min. All compounds described in Table [1] , separated from organic layers previously washed with aq NaHCO₃, brine and dried over anhyd Na₂SO₄, do not tolerate acidic conditions and cannot be purified by a traditional column chromatography on silica gel. On the other hand, fast flash chromatography (mixture of light petroleum/tert-butyl methyl ether) can be successfully used to remove 4-iodotoluene and to obtain acceptable quantity of all compounds showing high level of purity useful for spectroscopic identification. As matter of fact, authors of ref. [6] have isolated compound 6a and used it as glycosyl donor without any further purification. Spectral data of compounds 4a and 5a are identical with those reported in the literature. [9] The reaction conditions resumed above have been applied to alkynes. All the reactions reported in Table [2] are completed in less than 120 min and the crude materials isolated are successfully purified by flash chromatography (light petroleum/tert-butyl methyl ether) to obtain pure compounds. Products 2b, 3b, 4b have spectral data identical with those reported in the literature. [9]
The chemical shift δ on ¹⁹F NMR spectra are expressed in ppm using fluoro trichloromethane as internal reference. The presence of six natural isotopes of selenium leads to highly characteristic groups of peaks for selenium-containing fragments. The values reported below refer to the prominent peak.

16

Physical data of selected compounds: Compound 6a: ¹H NMR (300 MHz, CDCl₃): δ = 7.6-7.5 (m, 2 H), 7.4-7.2 (m, 18 H), 5.8 (dd, J = 2.4 Hz, J _H,F = 51.0 Hz, 1 H), 5.0-4.9 (ABq, J _AB = 10.5 Hz, 2 H), 4.8-4.5 (ABq, J _AB = 10.7 Hz, 2 H), 4.6-4.5 (ABq, J _AB = 12 Hz, 2 H), 4.1-3.9 (m, 2 H), 3.9-3.7 (m, 2 H), 3.7-3.6 (m, 1 H), 3.3 (ddd, J = 2.4 Hz, J = 11.2 Hz, J _H,F = 32.7 Hz, 1 H). ¹³C NMR (75 MHz, CDCl₃): δ = 138.0, 137.0, 134.0, 130.0, 129.0, 128.0, 108.5 (d, J _C,F = 218.7 Hz), 81.0, 79.5, 76.5, 75.0, 73.0, 69.0. ¹⁹F NMR (376 MHz, CDCl₃/C₆H₅CF₃): δ = -139.9 (dd, J = 51 Hz, J = 33 Hz, 1 F). GC-MS (EI): m/z (%) = 572 (1) [M⁺ - HF], 224 (1), 207(1), 161 (2), 157 (1), 105 (2), 91 (100), 77 (9). Compound 9a: ¹H NMR (200 MHz, CDCl₃): δ = 7.6-7.5 (m, 2 H), 7.4-7.3 (m, 3 H), 6.9 (d, J = 7.8 Hz, 1 H), 6.7, 6.6 (m, 3 H), 5.5 (br s, OH), 4.8 (dm, J _H,F = 47.8 Hz, 1 H), 3.8 (s, 3 H), 3.2, 2.9 (m, 4 H). ¹³C NMR (50 MHz, CDCl₃): δ = 146.3, 144.0, 133.0, 129.1, 128.1, 127.0, 122.0, 114.0, 112.0, 93.2 (d, J _C,F = 175.3 Hz), 55.8, 40.1 (d, J = 21.5 Hz), 30.9 (d, J = 23 Hz). ¹⁹F NMR (376 MHz, CDCl₃/C₆H₅CF₃): δ =
-171.8 to -172.2 (m, 1 F). GC-MS (EI): m/z (%) = 340 (8) [M⁺], 310 (2), 182 (9), 162 (25), 157 (30), 137 (77), 119 (15), 103 (19), 91 (31), 77 (80). Compound 1b: ¹H NMR (200 MHz, CDCl₃): δ = 7.6-7.5 (m, 2 H), 7.4-7.3 (m, 3 H), 2.7 (dq, J = 7.5 Hz, J _H,F = 23.0 Hz, 2 H), 2.4 (dq, J = 7.5 Hz, J _H,F = 2.7 Hz, 2 H), 1.1 (t, J = 7.5 Hz, 3 H), 1.0 (t, J = 7.5 Hz, 3 H). ¹³C NMR (50 MHz CDCl₃): δ = 164.0 (d, J _C,F = 267.5 Hz), 133.0, 129.2, 127.2, 110.0 (d, J _C,F = 21.5 Hz), 25.0 (d, J _C,F = 28.9 Hz), 24.0 (d, J _C,F = 7.0 Hz), 13.8, 11.8. ¹⁹F NMR (376 MHz, CDCl₃/C₆H₅CF₃): δ = -95.8 (dd, J = 23 Hz, 1 F). GC-MS (EI): m/z (%) = 258 (45) [M⁺], 229 (4), 183 (5), 157 (40), 137 (41), 117 (27), 55 (43), 77 (81), 73 (74), 59 (91), 51 (100).