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Synthesis 1997; 1997(6): 661-667
DOI: 10.1055/s-1997-1394
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Regioselective Synthesis of Substituted (3E)-1,3-Dienes from Chelated Allyl-Ironcarbene Complexes and Potassium Enoxyborates

Jutta Böhmer, Frank Hampel, Rainer Schobert*
  • *Institut für Organische Chemie der Universität Erlangen-Nürnberg, Henkestraße 42, D-91054 Erlangen, Germany, Fax +49(9131)856864; E-mail: schobert@organik.uni-erlangen.de
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Publication Date:
31 December 2000 (online)

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The addition of potassium enoxyborates to the chelated allyl-iron-carbene complex 1 leads to the corresponding η 4-(3E)-1,3-diene complexes 2 in fair yields. Complexes 2 can be demetalated with ceric ammonium nitrate (CAN) to give unrearranged (3E)-t-oxo-1,3-dienes 3. Prior to decomplexation, the carbonyl group can be further modified. This is demonstrated by the syntheses of the natural terpene alcohol hotrienol and of a complexed methylene-separated dienyne. Potassium enoxyborates are superior to lithium enolates as they are readily prepared in situ from a variety of aldehydes and ketones which do not form sufficiently stable lithium derivatives. In contrast to lithium enolates, only C-C coupling products derived from the "kinetic" regioisomers are formed from unsymmetrical aliphatic ketones.

organoiron compounds - carbene complexes - metallacycles - C-C coupling - (3E)-1,3-diene complexes