A Photoirradiative Phase-Vanishing Method: Efficient Generation of HBr from Alkanes and Molecular Bromine and Its Use for Subsequent Radical Addition to Terminal Alkenes

Abstract

A triphasic phase-vanishing (PV) system comprised of an alkane, perfluorohexanes, and bromine was successfully combined by photoirradiation to efficiently generate hydrogen bromide, which underwent radical addition with 1-alkenes in the hydrocarbon layer to afford terminal bromides in high yields.

fluorous solvent - phase-vanishing - photoirradiation - bromination - hydrogen bromide

References and Notes

1 For a general review on fluorous chemistry, see: Handbook of Fluorous Chemistry   Gladysz JA. Curran DP. Horváth IT. Wiley-VCH; Weinheim: 2004. 

For reviews on fluorous solvents, see:

2a Ryu I. Matsubara H. Emnet C. Gladysz JA. Takeuchi S. Nakamura Y. Curran DP. In Green Reaction Media in Organic Synthesis   Mikami K. Blackwell Publishing; Oxford: 2005.  p.59 

2b Matsubara H. Ryu I. In Green Separation Processes: Fundamentals and Applications   Afonso CAM. Crespo JG. Wiley-VCH; Weinheim: 2005.  p.219 

3 Matsubara H. Yasuda S. Sugiyama H. Ryu I. Fujii Y. Kita K. Tetrahedron  2002,  58:  4071 

4 Matsubara H. Maeda L. Ryu I. Chem. Lett.  2005,  34:  1548 

5 Matsubara H. Maeda L. Sugiyama H. Ryu I. Synthesis  2007,  2901 

For reviews on the ‘Phase-Vanishing’ method, see:

6a Ryu I. Matsubara H. Nakamura H. Curran DP. Chem. Rec.  2008,  8:  351 

6b Iskra J. Lett. Org. Chem.  2006,  3:  170 

7 Ryu I. Matsubara H. Yasuda S. Nakamura H. Curran DP. J. Am. Chem. Soc.  2002,  124:  12946 

8a Nakamura H. Usui T. Kuroda H. Ryu I. Matsubara H. Yasuda S. Curran DP. Org. Lett.  2003,  5:  1167 

8b Matsubara H. Yasuda S. Ryu I. Synlett  2003,  247 

8c Rahman MT. Kamata N. Matsubara H. Ryu I. Synlett  2005,  2664 

8d Matsubara H. Tsukida M. Yasuda S. Ryu I. J. Fluorine Chem.  2008,  129:  951 

9a Jana NK. Verkade JG. Org. Lett.  2003,  5:  3787 

9b Iskra J. Stavber S. Zupan M. Chem. Commun.  2003,  2496 

9c Curran DP. Werner S. Org. Lett.  2004,  6:  1021 

9d Podgoršek A. Stavber S. Zupan M. Iskra J. Eur. J. Org. Chem.  2006,  483 

9e Windmon N. Dragojlovic V. Tetrahedron Lett.  2008,  49:  6543 

9f Windmon N. Dragojlovic V. Beilstein J. Org. Chem.  2008,  4:  29 

9g Ma K. Li S. Weiss RG. Org. Lett.  2008,  10:  4155 

9h van Zee NJ. Dragojlovic V. Org. Lett.  2009,  11:  3190 

9i Pels K. Dragojlovic V. Beilstein J. Org. Chem.  2009,  5:  75 

10

^¹H NMR of the concentrated reaction mixture in entry 6 of Table 1 shows peaks assigned to 2-bromo-2,4,4-trimethyl-pentane as the product, suggesting that hydrogen abstraction from isooctane would occur selectively at the tertiary position of isooctane.

11a Brown HC. Lane CF. J. Am. Chem. Soc.  1970,  92:  7212 

11b Brown HC. Lane CF. Tetrahedron  1988,  44:  2763 

11c Falorni M. Lardicci L. Giacomelli G. J. Org. Chem.  1986,  51:  5291 

11d Brown HC. Lane CF. J. Am. Chem. Soc.  1970,  92:  6660 

11e Brown HC. Lane CF.
J. Chem. Soc. D: Chem. Commun.  1971,  521 

11f Lane CF. Brown HC. J. Organomet. Chem.  1971,  26:  C51 

11g Tufariello JJ. Hovey MM. J. Chem. Soc. D: Chem. Commun.  1970,  372 

11h Kabalka GW. Sastry KAR. Hsu HC. Hylarides MD. J. Org. Chem.  1981,  46:  3113 

11i Maruoka K. Sano H. Shinoda K. Nakai S. Yamamoto H. J. Am. Chem. Soc.  1986,  108:  6036 

11j Tufariello JJ. Hovey MM. J. Am. Chem. Soc.  1970,  92:  3221 

12a Tamao K. Yoshida J. Takahashi M. Yamamoto H. Kakui T. Matsumoto H. Kurita A. Kumada M. J. Am. Chem. Soc.  1978,  100:  290 

12b Tamao K. Yoshida J. Yamamoto H. Kakui T. Matsumoto H. Takahashi M. Kurita A. Murata M. Kumada M. Organometallics  1982,  1:  355 

13a Hart DW. Schwartz J. J. Am. Chem. Soc.  1974,  96:  8115 

13b Tolstikov GA. Miftakhov MS. Valeev FA. Izv. Akad. Nauk SSSR, Ser. Khim.  1979,  2576 

14a Isagaga K. Tatsumi K. Otsuji Y. Chem. Lett.  1977,  1117 

14b Sato F. Sato S. Kodama H. Sato M. J. Organomet. Chem.  1977,  142:  71 

14c Lee H.-S. Kim C.-E. J. Korean Chem. Soc.  2003,  47:  297 

14d Lee H.-S. Lee G.-Y. J. Korean Chem. Soc.  2005,  49:  321 

14e Gavrilenko VV. Kolesov VS. Zakharkin LI. Izv. Akad. Nauk SSSR, Ser. Khim.  1985,  681 

15

The reaction without fluorous phase gave an inferior result. For example, irradiation of a mixture of bromine (1.16 mmol) and isooctane (6 mL) with a 500 W Xe lamp for 30 min, followed by addition of 1-dodecene (1 mmol) at r.t., gave 1-bromododecane in 79% yield together with unreacted 1-dodecene (11%). In this procedure, probably some HBr generated would outgas during the reaction.

16 For an example of the use of HBr to prepare key substrates for sequential radical reactions, see: Zhang W. Hua Y. Geib SJ. Hoge G. Dowd P. Tetrahedron  1994,  50:  12579 

17

Typical Procedure for Photoirradiative Phase - Vanishing Hydrogen Bromide Addition to Alkenes (Table 2, entry 2): FC-72 (6 mL) was placed in a Pyrex test tube (13 mm
Æ × 105 mm) to which bromine (2.1 mmol, 340 mg) was added slowly using a glass pipette. Isooctane (1.5 mL) solution of 1-dodecene (2.0 mmol, 340 mg) was then added slowly, forming three layers. The test tube was irradiated with a 500 W Xenon lamp for 2 h. The isooctane layer was taken up with a pipette. Then, additional hexane (4 × 4 mL) was placed on the residual FC-72 layer, followed by decanting off. The combined organic layer was washed with aq 10% Na₂S₂O₃ (30 mL) and sat. brine (30 mL), dried over Na₂SO₄, and concentrated. Purification by a short column chromatography on silica gel with hexane gave 1-bromo-dodecane (480 mg, 96%).