Radical-induced SN1 substitution reactions

Tetrahedron Letters

Volumn 37, Issue 25, 1996, Pages 4365-4368

  Peukert, Stefan ^a   Giese, Bernd ^a  

^a UNIVERSITY OF BASEL   (Switzerland)

Author keywords

[No Author keywords available]

Indexed keywords

NUCLEOTIDE DERIVATIVE; RADICAL;

ARTICLE; CHEMICAL BOND; OXIDATION; PHOSPHORYLATION; PHOTOLYSIS; STEREOCHEMISTRY;

EID: 0030002632     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/0040-4039(96)00782-4     Document Type: Article

References (13)

1. a) B. Gicse, A. Dussy, C. Elie, P. Erdmann, U. Schwitter, Angew. Chem. Int. Ed. Engl. 1994, 33, 1861.
2. b) B. Giese, X. Beyrich-Graf, P. Erdmann, M. Petretta, U. Schwitter, Chem. & Biol. 1995, 2, 367. For pioneering work in this area, see:
3. c) G. Behrens, G. Koltzenburg, D. Schulte-Frohlinde, Z. Naturforsch. C 1982, 37, 1205.
4. a) H. Zipse, Angew. Chem. Int. Ed. Engl. 1994, 33, 1985.
5. b) D. P. Curran, Chemtracts Org. Chem. 1995, 8, 62.
6. The radical precursor 6 was synthesized according to the procedure described in B. Giese, P. Imwinkelried, M. Petretta, Synlett 1994, 1003.
7. The structures of compounds 8 and 9 were determined by comparison of the NMR data of analogous compounds described in: B. Giese, X. Beyrich-Graf, J. Burger, C. Kesselheim, M. Senn, T. Schäfer, Angew. Chem. Int. Ed. Engl. 1993, 32, 1742.
8. The use of diol 10 leads to radical 18 which is an enantiomeric analog of 7 (thymine is substituted by phenyl). We have used this system because 10 is readily available: E. T. Kool, N. Chaudhuri, Tetrahedron Lett. 1995, 36, 1795 and corrigendum, Tetrahedron Lett. 1995, 36, 4910.
9. The use of diol 10 leads to radical 18 which is an enantiomeric analog of 7 (thymine is substituted by phenyl). We have used this system because 10 is readily available: E. T. Kool, N. Chaudhuri, Tetrahedron Lett. 1995, 36, 1795 and corrigendum, Tetrahedron Lett. 1995, 36, 4910.
10. The stereochemistry of compounds 13a,b was assigned by NOE-experiments and by X-ray crystal structure analysis of 13b. The atomic coordinates for 13b are available on request from the Director of the Cambridge Crystallographic Data Centre, University Chemical Laboratories, Lensfield Road, Cambridge CB2 1EW. Any request should be accompanied by the full literature citation for this communication. The NMR signals of the methylene protons of the hydroxymethyl group are different in 13a and 13b. The cis orientation of the vicinal OH function in 13b leads to a downfield shift of about 0.2 ppm compared to 13a. Similar shift differences can also be observed in the 4 diastereomers of 19 and 20.
11. 3SnH.
12. 5 Silylation and methylation afforded two of the four diastereomers of 19 and 20. The other two diastereomers were prepared by silylation of the primary alcohol, inversion of the stereochemistry of the secondary alcohol by Mitsunobu reaction using benzoic acid, ester hydrolysis, and subsequent methylation.
13. -1). Thus, radical cation 24 is a strong oxidizing agent. The reduction of a similar radical cation is described in: B. Giese, J. Burger, T. W. Kang, C. Kesselheim, T. Wittmer, J. Am. Chem. Soc. 1992, 114, 7322.