Repository logo
 

Burnell, D. Jean

Permanent URI for this collectionhttps://hdl.handle.net/10222/27713

Browse

Recent Submissions

Now showing 1 - 5 of 5
  • Thumbnail Image
    ItemOpen Access
    cis-3,5-Cyclohexadiene-1,2-diol derivatives: facial selectivity in their Diels-Alder reactions with ethylenic, acetylenic and azo dienophiles
    (2006) Ogbomo, Sunny M.; Burnell, D. Jean
    The Diels - Alder reactions of maleimide with the acetonide derivative (6a) of cis-3,5-cyclohexadiene-1,2-diol (1a) in various solvents showed facial selectivities ranging from 1 : 1 to 1 : 9. The same derivative 6a reacted in benzene with ethylenic dienophiles with generally modest facial selectivity, but acetylenic dienophiles added exclusively anti to the oxygen functions of 6a. Dimerization of cyclic acetals 6a and 7 was mainly, but for 6a not exclusively, by anti addition with respect to both the diene and the dienophile partners. Reactions of azo dienophiles with derivatives of 1a were predominantly by anti addition, but the diol itself ( 1a) gave the syn adduct as the major product.
  • Thumbnail Image
    ItemOpen Access
  • Thumbnail Image
    ItemOpen Access
    Facial selectivity in the 4 + 2 reactions of a diene derived from carvone
    (Royal Society of Chemistry, 2006) Morrison, Christopher F.; Vaters, Jamie P.; Miller, David O.; Burnell, D. J.
    The facial selectivities of cyclohexadienes bearing isopropenyl and isopropyl groups as plane-nonsymmetric substituents were assessed in 4 + 2 reactions with N-phenylmaleimide, tetracyanoethylene and 4-phenyl-1,2,4- triazoline-3,5-dione. The only adducts were those arising by attack of the dienophile on the face of the diene opposite the isopropenyl or isopropyl group. In spite of some mechanistic similarities that tetracyanoethylene and 4-phenyl-1,2,4-triazoline-3,5-dione might have with the 4 + 2 addition of singlet oxygen, these dienophiles show none of the ability that singlet oxygen has shown to add syn to a plane-nonsymmetric isopropyl group. The Royal Society of Chemistry 2006.
  • Thumbnail Image
    ItemOpen Access
    Synthetic studies toward the kempane diterpenes. Construction of a key tricyclic intermediate
    (2005) Bao, GL; Zhao, L.; Burnell, DJ
    A synthetic sequence is described for construction of the tricyclic portion (35) of kempane diterpenes. The central stereochemistry was established by a Diels-Alder addition of 2,6-dimethyl-para-benzoquinone to a 5-membered, dithiane-protected diene, and the addition of acetylide, with very high chemoselectivity, provided a suitably functionalized handle that will be incorporated into the final seven-membered ring. The remaining stereogenic centres about the decalin moiety were established by a series of equilibration and reduction steps.
  • Thumbnail Image
    ItemOpen Access
    Vinylogous anionic processes in the formation and interconversion of tetracyclic ring systems
    (2011) Thornton, Paul D.; Cameron, T. Stanley; Burnell, D. Jean
    Tandem oxy-Cope and transannular vinylogous aldol reactions and/or vinylogous retro-aldol, conjugate addition, and transannular vinylogous aldol reactions transformed some tricyclic vinyl enones into fused tetracycles under basic conditions. Mesylates derived from similar tetracyclic products underwent efficient skeletal reorganization via transannular ring-opening but then different modes of transannular ring-closure upon treatment with tert-butoxide.