Stereoselective dimerisation at the end of a radical cascade sequence

Tetrahedron Letters

Volumn 40, Issue 30, 1999, Pages 5625-5628

  Boffey, Raymond J ^a   Whittingham, William G ^b   Kilburn, Jeremy D ^a  

^a UNIVERSITY OF SOUTHAMPTON   (United Kingdom)

^b JEALOTT S HILL RESEARCH STATION   (United Kingdom)

Author keywords

Cascade cyclisation; Dimerisation; Methylenecyclopropane; Samarium iodide

Indexed keywords

RADICAL; SAMARIUM;

ARTICLE; CARBON NUCLEAR MAGNETIC RESONANCE; CYCLIZATION; DIMERIZATION; DRUG SYNTHESIS; ENANTIOMER; SEQUENCE HOMOLOGY; STEREOCHEMISTRY;

EID: 0033166816     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(99)01046-1     Document Type: Article

References (18)

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10. Rajanbabu and others have shown that cyclisation of 2-(1-but-3-enyl)cyclohexyl radicals invariably gives cis-fused bicyclic products, but control of the stereochemistry of the additional chiral centre is critically dependent on whether the butenyl chain is axial or equatorial on the cyclohexyl radical transition state: a) RajanBabu, T. V. J. Am. Chem. Soc., 1987, 109, 609;
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15. 13C NMR spectrum of 17 was essentially identical to that for the dimer 18 (excepting for the signals of the ethylene bridge between the two monomer units). The structure of 18 was determined unequivocally by X-ray crystallographic analysis. (We thank A. Genge, University of Southampton for carrying out the analysis. Details will be published elsewhere.)
16. 2 solution - as in our work described here.
17. Stereoselective pinacol couplings are, of course, well known: Robertson, G. M. In Comprehensive Organic Synthesis (Vol 3), Trost, B. M.; Fleming, I., Eds.; Pergamon Press, 1991, 563-611, and the stereoselective β-dimerisation of 3,5,5 trimethylcyclohexenone, using organomanganese reagents, hasbeen described: Cahiez, G.; Alami, M. Tetrahedron Lett., 1986, 27, 569.
18. Stereoselective pinacol couplings are, of course, well known: Robertson, G. M. In Comprehensiveorganic Synthesis (Vol 3), Trost, B. M.; Fleming, I., Eds.; Pergamon Press, 1991, 563-611, and the Stereoselective β-dimerisation of 3,5,5 trimethylcyclohexenone, using organomanganese reagents, has been described: Cahiez, G.; Alami, M. Tetrahedron Lett., 1986, 27, 569.