Incorporation of an allene unit into alpha-pinene via beta-elimination

Kilbas B., Azizoglu A., Balci M.

HELVETICA CHIMICA ACTA, vol.89, no.7, pp.1449-1456, 2006 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 89 Issue: 7
  • Publication Date: 2006
  • Doi Number: 10.1002/hlca.200690145
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1449-1456
  • Middle East Technical University Affiliated: No


The two double-bond isomers 3-iodo-2,6,6-trimethylbicyclo[3.1.1]hept-2-ene (6b) and 3-iodo-4,6,6-trimethylbicyclo[3.1.1]hept-2-ene (11) were synthesized by reacting 2,6,6-trimethylbicyclo[3.1.1]heptan-3-one (9) with hydrazine, followed by treatment with 12 in the presence of Et3N. Treatment of 11 with t-BuOK as base in diglyme at 220 degrees resulted in the formation of 9 and 6,6-dimethyl-4-methylidene-bicyclo[3.1.1]hept-2-ene (12). For the formation of 9, the cyclic allene 7 is proposed as an intermediate. Treatment of the second isomer, 6b, with t-BuOK at 170 degrees gave rise to the diene 12 and the dimerization product 17. The underlying mechanism of this transformation is discussed. On the basis of density-functional-theory (DFT) calculations on the allene 7 and the alkyne 15, the formation of the latter as the intermediate was excluded.