Selective radical-chain epimerisation at C-H centres α to oxygen under conditions of polarity-reversal catalysis

Tetrahedron Letters

Volumn 40, Issue 22, 1999, Pages 4271-4274

  Dang, Hai Shan ^a   Roberts, Brian P ^a  

^a UNIVERSITY COLLEGE LONDON   (United Kingdom)

Author keywords

Catalysis; Epimerisation; Radicals and radical reactions; Thiols

Indexed keywords

CARBON; FREE RADICAL; HYDROXYL RADICAL; OXYGEN RADICAL; THIOL DERIVATIVE; TRI TERT BUTOXYSILANETHIOL; UNCLASSIFIED DRUG;

ARTICLE; CATALYSIS; CATALYST; CHIRALITY; DEPOLARIZATION; DIASTEREOISOMER; ENANTIOMER; OXIDATION; PHASE TRANSITION; STEREOISOMERISM; THERMOSTABILITY;

EID: 0033612179     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(99)00704-2     Document Type: Article

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8. 8
9. Busfield, W. K.; Grice, I. D.; Jenkins, I. D.; Monteiro, M. J. J. Chem. Soc., Perkin Trans. 2 1994, 1071. Busfield, W. K.; Grice, I. D.; Jenkins, I. D. J. Chem. Soc., Perkin Trans. 2 1994, 1079. Roberts, B. P.; Steel, A. J. J. Chem. Soc., Perkin Trans. 2 1994, 2411.
10. Busfield, W. K.; Grice, I. D.; Jenkins, I. D.; Monteiro, M. J. J. Chem. Soc., Perkin Trans. 2 1994, 1071. Busfield, W. K.; Grice, I. D.; Jenkins, I. D. J. Chem. Soc., Perkin Trans. 2 1994, 1079. Roberts, B. P.; Steel, A. J. J. Chem. Soc., Perkin Trans. 2 1994, 2411.
11. Busfield, W. K.; Grice, I. D.; Jenkins, I. D.; Monteiro, M. J. J. Chem. Soc., Perkin Trans. 2 1994, 1071. Busfield, W. K.; Grice, I. D.; Jenkins, I. D. J. Chem. Soc., Perkin Trans. 2 1994, 1079. Roberts, B. P.; Steel, A. J. J. Chem. Soc., Perkin Trans. 2 1994, 2411.
12. Obtained from Peroxid-Chemie and handled as a 50% w/w solution in involatile aliphatic hydrocarbons. The half-life of this peroxide is ca. 1 h at 125 °C.
13. The dioxolane 5-cis was prepared from commercial meso-butane-2,3-diol and contained 1% of the trans-isomer. Epimers were assumed to give equal GLC detector (flame-ionisation) response and this was demonstrated experimentally in the case of 5-cis and S-trans (prepared from the dl-diol).
14. Similarly, no epimerisation was observed when collidine (10 mol%) was also present.
15. 12SH available from the Aldrich Chemical Co.
16. It is thought likely that acid-catalysed elimination reactions lead to the formation of unsaturated compounds which act as inhibitors of the chain epimerisation process.
17. Cai, Y.; Roberts, B. P. J. Chem. Soc., Perkin Trans. 1 1998, 467 (corrigendum p. 3653). Dang, H.-S.; Roberts, B. P. J. Chem. Soc., Perkin Trans. 1 1998, 67. Dang, H.-S.; Kim, K.-M.; Roberts, B. P. Chem. Commun. 1998, 1413.
18. Cai, Y.; Roberts, B. P. J. Chem. Soc., Perkin Trans. 1 1998, 467 (corrigendum p. 3653). Dang, H.-S.; Roberts, B. P. J. Chem. Soc., Perkin Trans. 1 1998, 67. Dang, H.-S.; Kim, K.-M.; Roberts, B. P. Chem. Commun. 1998, 1413.
19. Cai, Y.; Roberts, B. P. J. Chem. Soc., Perkin Trans. 1 1998, 467 (corrigendum p. 3653). Dang, H.-S.; Roberts, B. P. J. Chem. Soc., Perkin Trans. 1 1998, 67. Dang, H.-S.; Kim, K.-M.; Roberts, B. P. Chem. Commun. 1998, 1413.
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21. PCMODEL, ver. 7.0 (Serena Software, Bloomington, IN 47402-3076, USA) was used for these calculations, in conjunction with the MMX force field and the GMMX stochastic conformational search routine. Enthalpy differences are reported.
22. 4 requires C, 55.2; H, 8.1%.
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27. 18b)