Polar substituent and solvent effects on the kinetics of radical reactions with thiols

Tetrahedron Letters

Volumn 37, Issue 33, 1996, Pages 5845-5848

  Tronche, Christopher ^a   Martinez, Felix N ^a   Horner, John H ^a   Newcomb, Martin ^a   Senn, Martin ^b   Giese, Bernd ^b  

^a WAYNE STATE UNIVERSITY   (United States)

^b UNIVERSITY OF BASEL   (Switzerland)

Author keywords

[No Author keywords available]

Indexed keywords

RADICAL; SOLVENT; THIOL DERIVATIVE; WATER;

AQUEOUS SOLUTION; ARTICLE; CHEMICAL REACTION KINETICS; CHEMICAL STRUCTURE; CYCLIZATION; NEODYMIUM LASER; PHOTOLYSIS; PULSE RADIOLYSIS; ULTRAVIOLET SPECTROSCOPY;

EID: 0030581388     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/0040-4039(96)01241-5     Document Type: Article

References (19)

1. 1. a) Leading reviews: Stubbe, J.; Kozarich, J. W. Chem. Rev. 1987, 87, 1107-1136;
2. b) Nicolaou, K. C.; Dai, W.-M. Angew. Chem. Int. Ed. Engl. 1991, 30, 1387-1416;
3. c) Pratviel, G.; Bernadou, J.; Meunier, B. Angew. Chem. Int. Ed. Engl. 1995, 34, 746-770.
4. 2. Giese, B.; Beyrich-Graf, X.; Erdmann, P.; Petretta, M.; Schwitter, U. Chem. & Biol. 1995, 2, 367-375.
5. 13C NMR spectroscopy and high resolution mass spectrometry.
6. 4. a) Newcomb, M.; Horner, J. H.; Filipkowski, M. A.; Ha, C.; Park, S. U. J. Am. Chem. Soc. 1995, 117, 3674-3684;
7. b) Johnson, C. C.; Horner, J. H.; Tronche, C.; Newcomb, M. J. Am. Chem. Soc. 1995, 117, 1684-1687.
8. 5. In early experiments K. U. Ingold and coworkers have observed that hexenyl radicals cyclize in hydrocarbons and THF with similar rates, see: Maeda, Y.; Schmid, P.; Griller, D.; Ingold, K. U. J. Chem. Soc., Chem. Commun. 1978, 525-526.
9. 6. About 0.040 mmol of the PTOC ester (Lusztyk, J.; Maillard, D.; Deycard S.; Lindsay, D. A.; Ingold, K. U. J. Org. Chem. 1987, 52, 3509-3514) was dissolved in degassed solvent (20 mL) under argon in a thermostated irradiation flask (Pyrex glass). After addition of the thiol (0.182 to 0.667 mmol), the reaction mixture was immediately irradiated with a 100 W tungsten filament bulb (Phillips Spotline R95) for 5 min at 30 °C. The products were detected by GC and identified by comparison with literature data (Walborsky, H. M.; Topolski, M.; Hamdouchi, C.; Pankowski, J. J. Org. Chem. 1992, 57, 6188-6191). The yield was nearly quantitative.
10. 6. About 0.040 mmol of the PTOC ester (Lusztyk, J.; Maillard, D.; Deycard S.; Lindsay, D. A.; Ingold, K. U. J. Org. Chem. 1987, 52, 3509-3514) was dissolved in degassed solvent (20 mL) under argon in a thermostated irradiation flask (Pyrex glass). After addition of the thiol (0.182 to 0.667 mmol), the reaction mixture was immediately irradiated with a 100 W tungsten filament bulb (Phillips Spotline R95) for 5 min at 30 °C. The products were detected by GC and identified by comparison with literature data (Walborsky, H. M.; Topolski, M.; Hamdouchi, C.; Pankowski, J. J. Org. Chem. 1992, 57, 6188-6191). The yield was nearly quantitative.
11. 7. a) Chatgilialoglu, C.; Ingold, K. U.; Scaiano, J. C. J. Am. Chem. Soc. 1981, 103, 7739-7742.
12. b) Franz, J. A.; Bushaw, B. A.; Alnajjar, M. S. J. Am. Chem. Soc. 1989, 111, 268-275.
13. 8. Rong, X. X.; Pan, H. Q.; Dolbier, W. R.; Smart, B. E. J. Am. Chem. Soc. 1994, 116, 4521-4522.
14. 9. Korth, H.-G.; Sustmann, R.; Giese, B.; Rückert, B.; Gröninger, K. S. Chem. Ber. 1990, 123, 1891-1898. In contrast to the stabilizing effect of α,β-dialkoxy substituents, a β-alkoxy substituent does not stabilize a radical; see: Crich, D.; Beckwith, A. L. J.; Chen, C.; Yao, Q.; Davison, I. G. E.; Longmore, R. W.; de Parrodi, C. A.; Quintero-Cortes, L.; Sandoval-Ramirez, J. J. Am Chem. Soc. 1995, 117, 8757-8768.
15. 9. Korth, H.-G.; Sustmann, R.; Giese, B.; Rückert, B.; Gröninger, K. S. Chem. Ber. 1990, 123, 1891-1898. In contrast to the stabilizing effect of α,β-dialkoxy substituents, a β-alkoxy substituent does not stabilize a radical; see: Crich, D.; Beckwith, A. L. J.; Chen, C.; Yao, Q.; Davison, I. G. E.; Longmore, R. W.; de Parrodi, C. A.; Quintero-Cortes, L.; Sandoval-Ramirez, J. J. Am Chem. Soc. 1995, 117, 8757-8768.
16. 10. Akhlaq, M. S.; Al-Baghdadi, S.; von Sonntag, C. Carbohydr. Res. 1987, 164, 71-83.
17. 11. Since the rates of cyclization reactions are slightly increased by increasing the polarity of the solvent (Table 1), the thiol trapping rates of Table 2 are the minimum values.
18. 12. An inverse solvent effect in H-transfer from the OH-group of phenols and hydroperoxides to alkoxyl radicals was observed by Lusztyk and coworkers: Avila, D. V.; Ingold, K. U.; Lusztyk, J.; Green, W. H.; Procopio, D. R. J. Am. Chem. Soc. 1995, 117, 2929-2930. The inverse solvent effect was explained by hydrogen bond donor effects of the solvent towards the OH group of the educts.
19. -1 at 30 °C in water as solvent (see also ref 10).