Conjugates of Bispidine and Monoterpenoids as Ligands of Metal Complex Catalysts for the Henry Reaction

Novel Bispidine-Monoterpene Conjugates—Synthesis and Application as Ligands for the Catalytic Ethylation of Chalcones

“…The product 37 was obtained by the interaction of N-benzylbispidinone 24 with camphor iodine derivative 31. Its formation required more severe conditions (increase of reaction temperature from 75 °C to 120 °C and reaction time from 2 h to 20 h) than for the previously described derivatives with pinane framework [8] which seemed to be associated with a higher steric hindrance of reaction center in the molecule of the terpene derivative. Bispidinone 16 without alkyl substituents at the nitrogen atom failed to interact with the camphor iodine derivative 31 under all studied conditions.…”

“…Subsequent acidic hydrolysis with aqueous hydrochloric acid solution yielded corresponding salt of bispidinone 16. By the interaction of diazaadamantanone 18 with benzyl chloride followed by KOH treatment of the resulting quaternary ammonium salt 23, monobenzyl-substituted bispidinone 24 was synthesized (Scheme 4) [8,28]. Hydrolysis of compound 23 with excess of alkali followed by acid treatment led to the formation of bispidinol 25.…”

“…Compound 26 was synthesized from diazaadamantane 20 by its subsequent interaction with benzyl chloride, treatment with potassium hydroxide in mixture H 2 O/CHCl 3 , introduction of tert-butoxycarbonyl protecting group and removal of benzyl fragment by Pd/C-H 2 system (Scheme 5). By the interaction of diazaadamantanone 18 with benzyl chloride followed b treatment of the resulting quaternary ammonium salt 23, monobenzyl-sub bispidinone 24 was synthesized (Scheme 4) [8,28]. Hydrolysis of compound 23 w cess of alkali followed by acid treatment led to the formation of bispidinol 25.…”

“…Previously we obtained disubstituted bispidinone 43 in [8] (Scheme 8). In the present work this compound was also synthesized by interaction of bispidinone 16 with corresponding monoterpenoid bromide in 74% yield.…”

“…Thus, relatively small ions of transition metals like Cu(II), Ni(II), Pd(II), Zn(II) are the most advantageous to form such compounds [6]. Complexes of substituted bispidines with transition metals have been investigated in Michael [7] and Henry reactions [8], deprotonation/electrophilic addition [9], oxidative kinetic separation of secondary alcohols [5], hydrogenation of double bonds [5], addition of diethylzinc to aldehydes [5,10] and others.…”