Reductive Electron Transfer in the Synthesis of Heterocycles

  • Andreas Gansäuer
  • Sven Hildebrandt
Part of the Topics in Heterocyclic Chemistry book series (TOPICS, volume 54)


This review summarizes the concepts involved in reductive electron transfer to organic substrates and subsequent heterocycle formation via radical intermediates. Furthermore, representative examples of existing methodologies are discussed that elucidate the scope and applicability of reductive electron transfer in heterocycle synthesis from simple five- and six-membered ring formation to complex structural motifs. The discussion mainly focuses on low-valent metal complexes as well as selected examples of organic ground-state reductants.


Catalysis Electron transfer Heterocycle Radical Reduction 



The authors gratefully acknowledge the support by the Jürgen Manchot Stiftung.


  1. 1.
    Renaud P, Sibi MP (2001) Radicals in organic synthesis. Wiley-VCH Verlag GmbH, WeinheimCrossRefGoogle Scholar
  2. 2.
    Gansäuer A (2006) Radicals in synthesis I. Top Curr Chem 263Google Scholar
  3. 3.
    Gansäuer A (2006) Radicals in synthesis II. Top Curr Chem 264Google Scholar
  4. 4.
    Heinrich M, Gansäuer A (2012) Radicals in synthesis III. Top Curr Chem 320Google Scholar
  5. 5.
    Noda D, Sunada Y, Hatakeyama T et al (2009) Effect of TMEDA on iron-catalyzed coupling reactions of ArMgX with alkyl halides. J Am Chem Soc 131(17):6078–6079. CrossRefPubMedGoogle Scholar
  6. 6.
    Saito T, Nishiyama H, Tanahashi H et al (2014) 1,4-Bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadienes as strong salt-free reductants for generating low-valent early transition metals with electron-donating ligands. J Am Chem Soc 136(13):5161–5170. CrossRefPubMedGoogle Scholar
  7. 7.
    Frey G, Hausmann JN, Streuff J (2015) Titanium-catalyzed reductive umpolung reactions with a metal-free terminal reducing agent. Chem Eur J 21(15):5693–5696. CrossRefPubMedGoogle Scholar
  8. 8.
    Beckwith AL, Schiesser CH (1985) Regio- and stereoselectivity of alkenyl radical ring closure: a theoretical study. Tetrahedron 41(19):3925–3941. CrossRefGoogle Scholar
  9. 9.
    Spellmeyer DC, Houk KN (1987) Force-field model for intramolecular radical additions. J Org Chem 52(6):959–974. CrossRefGoogle Scholar
  10. 10.
    Gansäuer A, Pierobon M, Bluhm H (2002) Stereoselective synthesis of tri- and tetrasubstituted olefins by tandem cyclization addition reactions featuring vinyl radicals. Angew Chem Int Ed 41(17):3206–3208.<3206:AID-ANIE3206>3.0.CO;2-2 CrossRefGoogle Scholar
  11. 11.
    Gansäuer A, Rinker B, Pierobon M et al (2003) A radical tandem reaction with homolytic cleavage of a Ti-O bond. Angew Chem Int Ed 42(31):3687–3690. CrossRefGoogle Scholar
  12. 12.
    Gansäuer A, Rinker B, Ndene-Schiffer N et al (2004) A radical roundabout for an unprecedented tandem reaction including a homolytic substitution with a titanium-oxygen bond. Eur J Org Chem 2004(11):2337–2351. CrossRefGoogle Scholar
  13. 13.
    Gansäuer A, Fleckhaus A, Lafont MA et al (2009) Catalysis via homolytic substitutions with C-O and Ti-O bonds: oxidative additions and reductive eliminations in single electron steps. J Am Chem Soc 131(46):16989–16999. CrossRefPubMedGoogle Scholar
  14. 14.
    Wu X, See JWT, Xu K et al (2014) A general palladium-catalyzed method for alkylation of heteroarenes using secondary and tertiary alkyl halides. Angew Chem Int Ed 53(49):13573–13577. CrossRefGoogle Scholar
  15. 15.
    Aulenta F, Wefelscheid UK, Brüdgam I et al (2008) Nitrogen-containing tricyclic and tetracyclic compounds by stereoselective samarium diiodide promoted cyclizations of quinolyl-substituted ketones – a new access to azasteroids. Eur J Org Chem 2008(13):2325–2335. CrossRefGoogle Scholar
  16. 16.
    Kochi JK (2002) Homocoupling, disproportionation and cross-coupling of alkyl groups. Role of the transition metal catalyst. J Organomet Chem 653(1–2):11–19. CrossRefGoogle Scholar
  17. 17.
    Vaupel A, Knochel P (1994) Stereoselective synthesis of substituted tetrahydrofurans and butyrolactones by a new nickel catalyzed carbozincation. Tetrahedron Lett 35(45):8349–8352. CrossRefGoogle Scholar
  18. 18.
    Vaupel A, Knochel P (1995) A short formal synthesis of (-)-methylenolactocin via a nickel catalyzed intramolecular carbozincation. Tetrahedron Lett 36(2):231–232. CrossRefGoogle Scholar
  19. 19.
    Vaupel A, Knochel P (1996) Stereoselective synthesis of heterocyclic zinc reagents via a nickel-catalyzed radical cyclization. J Org Chem 61(17):5743–5753. CrossRefGoogle Scholar
  20. 20.
    Ohmiya H, Wakabayashi K, Yorimitsu H et al (2006) Cobalt-catalyzed cross-coupling reactions of alkyl halides with aryl Grignard reagents and their application to sequential radical cyclization/cross-coupling reactions. Tetrahedron 62(10):2207–2213. CrossRefGoogle Scholar
  21. 21.
    Fujioka T, Nakamura T, Yorimitsu H et al (2002) Cobalt-catalyzed intramolecular heck-type reaction of 6-halo-1-hexene derivatives. Org Lett 4(13):2257–2259. CrossRefPubMedGoogle Scholar
  22. 22.
    Li G, Kuo JL, Han A et al (2016) Radical isomerization and cycloisomerization initiated by H• transfer. J Am Chem Soc 138(24):7698–7704. CrossRefPubMedGoogle Scholar
  23. 23.
    Ueno Y, Chino K, Watanabe M et al (1982) Homolytic carbocyclization by use of a heterogeneous supported organotin catalyst. A new synthetic route to 2-alkoxytetrahydrofurans and butyrolactones. J Am Chem Soc 104(20):5564–5566. CrossRefGoogle Scholar
  24. 24.
    Stork G, Mook R, Biller SA et al (1983) Free-radical cyclization of bromo acetals. Use in the construction of bicyclic acetals and lactones. J Am Chem Soc 105(11):3741–3742. CrossRefGoogle Scholar
  25. 25.
    Villar F, Renaud P (1998) Diastereoselective radical cyclization of bromoacetals (Ueno-stork reaction) controlled by the acetal center. Tetrahedron Lett 39(47):8655–8658. CrossRefGoogle Scholar
  26. 26.
    Zhou L, Hirao T (2003) A novel titanium-catalyzed cyclization of olefinic iodoethers to tetrahydrofurans. J Org Chem 68(4):1633–1635. CrossRefPubMedGoogle Scholar
  27. 27.
    Hackmann C, Schäfer HJ (1993) New methods for reductive free-radical cyclizations of bromoacetals to 2-alkoxytetrahydrofurans with activated chromium(II)-acetate. Tetrahedron 49(21):4559–4574. CrossRefGoogle Scholar
  28. 28.
    Inoue R, Nakao J, Shinokubo H et al (1997) Radical cyclization of allyl 2-iodophenyl ether, N,N-diallyl-2-iodoaniline, and 2-iodoethanal acetal by means of trialkylmanganate(II). Bull Chem Soc Jpn 70(9):2039–2049. CrossRefGoogle Scholar
  29. 29.
    Nakao J, Inoue R, Shinokubo H et al (1997) Trialkylmanganate-induced cyclization of allyl 2-iodophenyl ether, N,N-diallyl-2-iodoaniline, and alpha-iodo acetal. J Org Chem 62(7):1910–1911. CrossRefPubMedGoogle Scholar
  30. 30.
    Hayashi Y, Shinokubo H, Oshima K (1998) Intramolecular radical cyclization of 2-haloethanal allyl acetal and allyl 2-halophenyl ether with a grignard reagent in the presence of iron(II) chloride. Tetrahedron Lett 39(1–2):63–66. CrossRefGoogle Scholar
  31. 31.
    Giese B, Erdmann P, Göbel T et al (1992) Cobalt-catalyzed carbon-carbon bond formation via radicals. Tetrahedron Lett 33(32):4545–4548. CrossRefGoogle Scholar
  32. 32.
    Murphy JA, Khan TA, Zhou S et al (2005) Highly efficient reduction of unactivated aryl and alkyl iodides by a ground-state neutral organic electron donor. Angew Chem Int Ed 44(9):1356–1360. CrossRefGoogle Scholar
  33. 33.
    Fujita K, Nakamura T, Yorimitsu H et al (2001) Triethylborane-induced radical reaction with Schwartz reagent. J Am Chem Soc 123(13):3137–3138. CrossRefGoogle Scholar
  34. 34.
    Fujita K, Yorimitsu H, Oshima K (2002) Radical cyclization reactions with a zirconocene-olefin complex as an efficient single electron transfer reagent. Synlett 2002(2):337–339. CrossRefGoogle Scholar
  35. 35.
    MacLeod KC, Patrick BO, Smith KM (2010) Chromium-catalyzed radical cyclization of bromo and chloro acetals. Organometallics 29(24):6639–6641. CrossRefGoogle Scholar
  36. 36.
    Martin R, Fürstner A (2004) Cross-coupling of alkyl halides with aryl grignard reagents catalyzed by a low-valent iron complex. Angew Chem Int Ed 43(30):3955–3957. CrossRefGoogle Scholar
  37. 37.
    Bloome KS, McMahen RL, Alexanian EJ (2011) Palladium-catalyzed heck-type reactions of alkyl iodides. J Am Chem Soc 133(50):20146–20148. CrossRefPubMedGoogle Scholar
  38. 38.
    Liu Q, Dong X, Li J et al (2015) Recent advances on palladium radical involved reactions. ACS Catal 5(10):6111–6137. CrossRefGoogle Scholar
  39. 39.
    Ozaki S, Matsushita H, Ohmori H (1992) Indirect electroreductive radical cyclization of halogeno ethers using nickel(II) complexes as electron-transfer catalysts. J Chem Soc Chem Commun 16:1120. CrossRefGoogle Scholar
  40. 40.
    Dong X, Han Y, Yan F et al (2016) Palladium-catalyzed 6-endo selective alkyl-heck reactions: access to 5-phenyl-1,2,3,6-tetrahydropyridine derivatives. Org Lett 18(15):3774–3777. CrossRefPubMedGoogle Scholar
  41. 41.
    Hutchinson JH, Pattenden G, Myers PL (1987) Tandem radical cyclisation – intramolecular Mukaiyama aldolisation approach to forskolin. Tetrahedron Lett 28(12):1313–1316. CrossRefGoogle Scholar
  42. 42.
    Busato S, Tinembart O, Zhang Z et al (1990) Vitamin B12, a catalyst in the synthesis of prostaglandins. Tetrahedron 46(9):3155–3166. CrossRefGoogle Scholar
  43. 43.
    Mayer S, Prandi J, Bamhaoud T et al (1998) Synthesis of perhydro-furo[2,3-b]pyran (and furan)-3-yl methanols by oxygenative radical cyclization. Tetrahedron 54(30):8753–8770. CrossRefGoogle Scholar
  44. 44.
    Cahiez G, Moyeux A (2010) Cobalt-catalyzed cross-coupling reactions. Chem Rev 110(3):1435–1462. CrossRefPubMedGoogle Scholar
  45. 45.
    Wakabayashi K, Yorimitsu H, Oshima K (2001) Cobalt-catalyzed tandem radical cyclization and cross-coupling reaction – its application to Benzyl-substituted heterocycles. J Am Chem Soc 123(22):5374–5375. CrossRefPubMedGoogle Scholar
  46. 46.
    Tsuji T, Yorimitsu H, Oshima K (2002) Cobalt-catalyzed coupling reaction of alkyl halides with allylic grignard reagents. Angew Chem Int Ed 41(21):4137–4139.<4137:AID-ANIE4137>3.0.CO;2-0 CrossRefGoogle Scholar
  47. 47.
    Ohmiya H, Tsuji T, Yorimitsu H et al (2004) Cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic and benzylic Grignard reagents and their application to tandem radical cyclization/cross-coupling reactions. Chem Eur J 10(22):5640–5648. CrossRefPubMedGoogle Scholar
  48. 48.
    Ohmiya H, Yorimitsu H, Oshima K (2006) Cobalt-mediated cross-coupling reactions of primary and secondary alkyl halides with 1-(trimethylsilyl)ethenyl- and 2-trimethylsilylethynylmagnesium reagents. Org Lett 8(14):3093–3096. CrossRefPubMedGoogle Scholar
  49. 49.
    Someya H, Ohmiya H, Yorimitsu H et al (2007) N-heterocyclic carbene ligands in cobalt-catalyzed sequential cyclization/cross-coupling reactions of 6-halo-1-hexene derivatives with Grignard reagents. Org Lett 9(8):1565–1567. CrossRefPubMedGoogle Scholar
  50. 50.
    Barré B, Gonnard L, Campagne R et al (2014) Iron- and cobalt-catalyzed arylation of azetidines, pyrrolidines, and piperidines with Grignard reagents. Org Lett 16(23):6160–6163. CrossRefPubMedGoogle Scholar
  51. 51.
    Fürstner A, Martin R, Krause H et al (2008) Preparation, structure, and reactivity of nonstabilized organoiron compounds. Implications for iron-catalyzed cross coupling reactions. J Am Chem Soc 130(27):8773–8787. CrossRefPubMedGoogle Scholar
  52. 52.
    Powell DA, Maki T, Fu GC (2005) Stille cross-couplings of unactivated secondary alkyl halides using monoorganotin reagents. J Am Chem Soc 127(2):510–511. CrossRefPubMedGoogle Scholar
  53. 53.
    González-Bobes F, Fu GC (2006) Amino alcohols as ligands for nickel-catalyzed suzuki reactions of unactivated alkyl halides, including secondary alkyl chlorides, with arylboronic acids. J Am Chem Soc 128(16):5360–5361. CrossRefPubMedGoogle Scholar
  54. 54.
    Phapale VB, Buñuel E, García-Iglesias M et al (2007) Ni-catalyzed cascade formation of C(sp3)-C(sp3) bonds by cyclization and cross-coupling reactions of iodoalkanes with alkyl zinc halides. Angew Chem Int Ed 46(46):8790–8795. CrossRefGoogle Scholar
  55. 55.
    Ishiyama T, Murata M, Suzuki A et al (1995) Synthesis of ketones from iodoalkenes, carbon monoxide and 9-alkyl-9-borabicyclo[3.3.1]nonane derivatives via a radical cyclization and palladium-catalysed carbonylative cross-coupling sequence. J Chem Soc Chem Commun 3:295. CrossRefGoogle Scholar
  56. 56.
    Xue W, Qu Z, Grimme S et al (2016) Copper-catalyzed cross-coupling of silicon pronucleophiles with unactivated alkyl electrophiles coupled with radical cyclization. J Am Chem Soc 138(43):14222–14225. CrossRefPubMedGoogle Scholar
  57. 57.
    Procter DJ, Flowers RA, Skrydstrup T (2009) Organic synthesis using samarium diiodide. Royal Society of Chemistry, CambridgeGoogle Scholar
  58. 58.
    Szostak M, Fazakerley NJ, Parmar D et al (2014) Cross-coupling reactions using samarium(II) iodide. Chem Rev 114(11):5959–6039. CrossRefPubMedGoogle Scholar
  59. 59.
    Shirahama H, Kamabe M, Miyazaki T et al (2002) Formal synthesis of FPA, a kainoid amino acid, via ketyl radical cyclization. Heterocycles 56(1–2):105. CrossRefGoogle Scholar
  60. 60.
    Molander GA, Cormier EP (2005) Ketyl-allene cyclizations promoted by samarium(II) iodide. J Org Chem 70(7):2622–2626. CrossRefPubMedGoogle Scholar
  61. 61.
    Nakata T (2010) SmI(2)-induced reductive cyclizations for the synthesis of cyclic ethers and applications in natural product synthesis. Chem Soc Rev 39(6):1955–1972. CrossRefPubMedGoogle Scholar
  62. 62.
    Kimura T, Nakata T (2010) SmI2-induced cyclization of (E)- and (Z)-β-alkoxyvinyl sulfones with aldehydes. Tetrahedron Asymmetry 21(11–12):1389–1395. CrossRefGoogle Scholar
  63. 63.
    Kimura T, Hagiwara M, Nakata T (2009) SmI2-induced cyclization of optically active (E)- and (Z)-alkoxyvinyl sulfoxides with aldehydes. Tetrahedron 65(52):10893–10900. CrossRefGoogle Scholar
  64. 64.
    Kimura T, Nakata T (2007) SmI2-induced reductive cyclization of (E)- and (Z)-alkoxyvinyl sulfones with aldehyde. Tetrahedron Lett 48(1):43–46. CrossRefGoogle Scholar
  65. 65.
    Kimura T, Hagiwara M, Nakata T (2007) SmI2-induced reductive cyclization of optically active-alkoxyvinyl sulfoxides with aldehyde. Tetrahedron Lett 48(52):9171–9175. CrossRefGoogle Scholar
  66. 66.
    Takahashi K, Honda T (2010) Diastereoselective syntheses of functionalized five-membered carbocycles and heterocycles by a SmI2-promoted intramolecular coupling of bromoalkynes and alpha,beta-unsaturated esters. Org Lett 12(13):3026–3029. CrossRefPubMedGoogle Scholar
  67. 67.
    Hölemann A, Reissig H (2004) Samarium diiodide in the synthesis of medium-sized rings – carbocycles and heterocycles by intramolecular addition of samarium ketyls to alkynes. Synlett 15:2732–2735. CrossRefGoogle Scholar
  68. 68.
    Nugent WA, RajanBabu TV (1988) Transition-metal-centered radicals in organic synthesis. Titanium(III)-induced cyclization of epoxy-olefins. J Am Chem Soc 110(25):8561–8562. CrossRefGoogle Scholar
  69. 69.
    RajanBabu TV, Nugent WA (1989) Intermolecular addition of epoxides to activated olefins: a new reaction. J Am Chem Soc 111(12):4525–4527. CrossRefGoogle Scholar
  70. 70.
    RajanBabu TV, Nugent WA, Beattie MS (1990) Free radical-mediated reduction and deoxygenation of epoxides. J Am Chem Soc 112(17):6408–6409. CrossRefGoogle Scholar
  71. 71.
    RajanBabu TV, Nugent WA (1994) Selective generation of free radicals from epoxides using a transition-metal radical. A powerful new tool for organic synthesis. J Am Chem Soc 116(3):986–997. CrossRefGoogle Scholar
  72. 72.
    Gansäuer A, Otte M, Shi L (2011) Radical cyclizations terminated by Ir-catalyzed hydrogen atom transfer. J Am Chem Soc 133(3):416–417. CrossRefPubMedGoogle Scholar
  73. 73.
    Gansäuer A, Fan C, Keller F et al (2007) Regiodivergent epoxide opening: a concept in stereoselective catalysis beyond classical kinetic resolutions and desymmetrizations. Chem Eur J 13(29):8084–8090. CrossRefPubMedGoogle Scholar
  74. 74.
    Gansäuer A, Karbaum P, Schmauch D et al (2014) Synthetic and computational evaluation of regiodivergent epoxide opening for diol and polyol synthesis. Chem Asian J 9(8):2289–2294. CrossRefPubMedGoogle Scholar
  75. 75.
    Funken N, Mühlhaus F, Gansäuer A (2016) General, highly selective synthesis of 1,3- and 1,4-difunctionalized building blocks by regiodivergent epoxide opening. Angew Chem Int Ed 55(39):12030–12034. CrossRefGoogle Scholar
  76. 76.
    Chakraborty TK, Samanta R, Roy S et al (2009) Ti(III)-mediated radical cyclization of β-aminoacrylate containing epoxy-alcohol moieties: synthesis of highly substituted azacycles. Tetrahedron Lett 50(26):3306–3310. CrossRefGoogle Scholar
  77. 77.
    Hilt G, Bolze P, Kieltsch I (2005) An iron-catalysed chemo- and regioselective tetrahydrofuran synthesis. Chem Commun 15:1996–1998. CrossRefGoogle Scholar
  78. 78.
    Hilt G, Walter C, Bolze P (2006) Iron-salen complexes as efficient catalysts in ring expansion reactions of epoxyalkenes. Adv Synth Catal 348(10–11):1241–1247. CrossRefGoogle Scholar
  79. 79.
    Hilt G, Bolze P, Harms K (2007) An improved catalyst system for the iron-catalyzed intermolecular ring-expansion reactions of epoxides. Chem Eur J 13(15):4312–4325. CrossRefPubMedGoogle Scholar
  80. 80.
    Marcelo F, Jiménez-Barbero J, Marrot J et al (2008) Stereochemical assignment and first synthesis of the core of miharamycin antibiotics. Chem Eur J 14(32):10066–10073. CrossRefPubMedGoogle Scholar
  81. 81.
    Cha JY, Yeoman JTS, Reisman SE (2011) A concise total synthesis of (-)-maoecrystal Z. J Am Chem Soc 133(38):14964–14967. CrossRefPubMedGoogle Scholar
  82. 82.
    Huang H, Procter DJ (2016) Radical-radical cyclization cascades of barbiturates triggered by electron-transfer reduction of amide-type carbonyls. J Am Chem Soc 138(24):7770–7775. CrossRefPubMedGoogle Scholar
  83. 83.
    Bichovski P, Haas TM, Kratzert D et al (2015) Synthesis of bridged benzazocines and benzoxocines by a titanium-catalyzed double-reductive umpolung strategy. Chem Eur J 21(6):2339–2342. CrossRefPubMedGoogle Scholar
  84. 84.
    Zheng X, He J, Li H et al (2015) Titanocene(III)-catalyzed three-component reaction of secondary amides, aldehydes, and electrophilic alkenes. Angew Chem Int Ed 54(46):13739–13742. CrossRefGoogle Scholar
  85. 85.
    Zheng X, Dai X, Yuan H et al (2013) Umpolung of hemiaminals: titanocene-catalyzed dehydroxylative radical coupling reactions with activated alkenes. Angew Chem Int Ed 52(12):3494–3498. CrossRefGoogle Scholar
  86. 86.
    Dahlen A, Petersson A, Hilmersson G (2003) Diastereoselective intramolecular SmI2-H2O-amine mediated couplings. Org Biomol Chem 1(14):2423–2426. CrossRefPubMedGoogle Scholar
  87. 87.
    Inanaga J, Ujikawa O, Yamaguchi M (1991) Sml2-promoted aryl radical cyclization. A new synthetic entry into heterocycles. Tetrahedron Lett 32(14):1737–1740. CrossRefGoogle Scholar
  88. 88.
    Clark AJ, Davies DI, Jones K et al (1994) Cobalt(II) Chloride-Grignard reagent: an alternative to tin hydride in aryl radical cyclisations. J Chem Soc Chem Commun 41(1):41–42. CrossRefGoogle Scholar
  89. 89.
    Bhandal H, Patel VF, Pattenden G et al (1990) Cobalt-mediated radical reactions in organic synthesis. Oxidative cyclisations of aryl and alkyl halides leading to functionalised reduced heterocycles and butyrolactones. J Chem Soc Perkin Trans 1(10):2691. CrossRefGoogle Scholar
  90. 90.
    Dunach E, Esteves A, Medeiros MJ et al (2004) The study of nickel(II) and cobalt(II) complexes with a chiral salen derivative as catalysts for the electrochemical cyclisation of unsaturated 2-bromophenyl ethers. J Electroanal Chem 566(1):39–45. CrossRefGoogle Scholar
  91. 91.
    Nii S, Terao J, Kambe N (2000) Titanocene-catalyzed carbosilylation of alkenes and dienes using alkyl halides and chlorosilanes. J Org Chem 65(17):5291–5297. CrossRefPubMedGoogle Scholar
  92. 92.
    Nii S, Terao J, Kambe N (2004) Titanocene-catalyzed regioselective carbomagnesation of alkenes and dienes. J Org Chem 69(2):573–576. CrossRefPubMedGoogle Scholar
  93. 93.
    Broggi J, Terme T, Vanelle P (2014) Organic electron donors as powerful single-electron reducing agents in organic synthesis. Angew Chem Int Ed 53(2):384–413. CrossRefGoogle Scholar
  94. 94.
    Barham JP, Coulthard G, Emery KJ et al (2016) KOtBu: a privileged reagent for electron transfer reactions? J Am Chem Soc 138(23):7402–7410. CrossRefPubMedGoogle Scholar
  95. 95.
    Sun C, Gu Y, Wang B et al (2011) Direct arylation of alkenes with aryl iodides/bromides through an organocatalytic radical process. Chem Eur J 17(39):10844–10847. CrossRefPubMedGoogle Scholar
  96. 96.
    Lampard C, Murphy JA, Lewis N (1993) Tetrathiafulvalene as a catalyst for radical-polar crossover reactions. J Chem Soc Chem Commun 56(3):295–297. CrossRefGoogle Scholar
  97. 97.
    Iwasaki H, Eguchi T, Tsutsui N et al (2008) Samarium(II)-mediated spirocyclization by intramolecular aryl radical addition onto an aromatic ring. J Org Chem 73(18):7145–7152. CrossRefPubMedGoogle Scholar
  98. 98.
    Ohno H, Iwasaki H, Eguchi T et al (2004) The first samarium(II)-mediated aryl radical cyclisation onto an aromatic ring. Chem Commun 19:2228–2229. CrossRefGoogle Scholar
  99. 99.
    Roman DS, Takahashi Y, Charette AB (2011) Potassium tert-butoxide promoted intramolecular arylation via a radical pathway. Org Lett 13(12):3242–3245. CrossRefPubMedGoogle Scholar
  100. 100.
    Wang J, Su Y, Yin F et al (2014) Pd(0)-catalyzed radical aryldifluoromethylation of activated alkenes. Chem Commun 50(31):4108–4111. CrossRefGoogle Scholar
  101. 101.
    Wang H, Guo LN, Duan X (2016) Palladium-catalyzed alkylarylation of acrylamides with unactivated alkyl halides. J Org Chem 81(3):860–867. CrossRefPubMedGoogle Scholar
  102. 102.
    Zheng J, Chen P, Yuan Y et al (2017) Pd-catalyzed arylperfluoroalkylation of unactivated olefins for the synthesis of heterocycles. J Org Chem 82(11):5790–5797. CrossRefPubMedGoogle Scholar
  103. 103.
    Xuan J, Daniliuc CG, Studer A (2016) Construction of polycyclic γ-lactams and related heterocycles via electron catalysis. Org Lett 18(24):6372–6375. CrossRefPubMedPubMedCentralGoogle Scholar
  104. 104.
    Wipf P, Maciejewski JP (2008) Titanocene(III)-catalyzed formation of indolines and azaindolines. Org Lett 10(19):4383–4386. CrossRefPubMedPubMedCentralGoogle Scholar
  105. 105.
    Gansäuer A, Behlendorf M, von Laufenberg D et al (2012) Catalytic, atom-economical radical arylation of epoxides. Angew Chem Int Ed 51(19):4739–4742. CrossRefGoogle Scholar
  106. 106.
    Gansäuer A, Seddiqzai M, Dahmen T et al (2013) Computational study of the rate constants and free energies of intramolecular radical addition to substituted anilines. Beilstein J Org Chem 9:1620–1629. CrossRefPubMedPubMedCentralGoogle Scholar
  107. 107.
    Gansäuer A, Hildebrandt S, Michelmann A et al (2015) Cationic titanocene(III) complexes for catalysis in single-electron steps. Angew Chem Int Ed 54(24):7003–7006. CrossRefGoogle Scholar
  108. 108.
    Gansäuer A, von Laufenberg D, Kube C et al (2015) Mechanistic study of the titanocene(III)-catalyzed radical arylation of epoxides. Chem Eur J 21(1):280–289. CrossRefPubMedGoogle Scholar
  109. 109.
    Gansäuer A, Hildebrandt S, Vogelsang E et al (2016) Tuning the redox properties of the titanocene(III)/(IV)-couple for atom-economical catalysis in single electron steps. Dalton Trans 45(2):448–452. CrossRefPubMedGoogle Scholar
  110. 110.
    Hildebrandt S, Gansäuer A (2016) Synthesis of dihydropyrrolizine and tetrahydroindolizine scaffolds from pyrroles by titanocene(III) catalysis. Angew Chem Int Ed 55(33):9719–9722. CrossRefGoogle Scholar
  111. 111.
    Hildebrandt S, Schacht J, Gansäuer A (2017) Epoxides as precursors to 1-hydroxymethyl indolizidine and pyrrolizidine. Synthesis 49(13):2943–2948. CrossRefGoogle Scholar

Copyright information

© Springer International Publishing AG, part of Springer Nature 2017

Authors and Affiliations

  1. 1.Kekulé-Institut für Organische Chemie und Biochemie Universität BonnBonnGermany

Personalised recommendations