5628-20-6Relevant articles and documents
The first regioselective double electrophilic substitution of the C2-symmetric pseudo-meta-disubstituted [2.2]paracyclophanes
Vorontsova, Natalia V.,Vorontsov, Evgenii V.,Sergeeva, Elena V.,Rozenberg, Valeria I.
, p. 2357 - 2360 (2006)
We report here the first examples of the regioselective double electrophilic substitution of chiral C2-symmetric pseudo-meta-disubstituted [2.2]paracyclophanes. Thus, the double acylation of 4,15-dihydroxy[2.2]paracyclophane occurs ortho-regioselectively, whereas the double acylation of its respective dimethyl ether is completely para-regioselective. Double bromination of 4,15-dicarbomethoxy[2.2]paracyclophane regioselectively generates the pseudo-gem-substitution pattern. The approaches elaborated allow the synthesis of all three possible types of chiral bis-bifunctional compounds, which have two independent, although chemically and stereochemically equal, functional fragments with pseudo-meta mutual orientation of both pairs of identical substituents.
Symmetrically tetrasubstituted [2.2]paracyclophanes: Their systematization and regioselective synthesis of several types of bis-bifunctional derivatives by double electrophilic substitution
Vorontsova, Natalia V.,Rozenberg, Valeria I.,Sergeeva, Elena V.,Vorontsov, Evgenii V.,Starikova, Zoya A.,Lyssenko, Konstantin A.,Hopf, Henning
experimental part, p. 4600 - 4617 (2009/05/08)
The possible number of chiral and achiral tetrasubstituted [2.2]paracyclophanes possessing different types of symmetry (C2, Ci, Cs, C2., C2h) is evaluated and a unified independent trivial naming descriptor system is introduced. The reactivity and regioselectivity of the electrophilic substitution of the chiral pseudo-mefaand achiral pseudo-para-disubstituted [2.2]paracyclophanes are investigated in an approach suggested to be general for the synthesis of bis-bifunctional [2.2]paracyclophanes. The mono- and diacylation of chiral pseudo-meta-dihydroxy[2.2]paracyclophane 14 with acetylchloride occur ortho-regioselectively to produce tri- 22, 23 and symmetrically 21 tetrasubstituted acyl derivatives. The same reaction with benzoylchloride is neither regio-, nor chemoselective, and gives rise to a mixture of ortho-lpara-, mono-/diacylated compounds 27-31. The double acylation of pseudo-meta- dimethoxy[2.2]paracyclophane 18 is completely para-regioselective. Electrophilic substitution of pseudo-wera-bis(methoxycarbonyl)[2.2]paracyclophane 20 regioselectively generates the pseudo-gem-substitution pattern. Formylation of this substrate produces the monocarbonyl derivatives 35 only, whereas the Fe-catalyzed bromination may be directed towards mono- 36 or disubstitution 37 products chemoselectively by varying the reactions conditions. The diacylation and dibromination reactions of the respective achiral diphenol 12 and bis(methoxycarbonyl) 40 derivatives of the pseudo-para-structure retain regioselectivities which are characteristic for their pseudo-mefa-regioisomers. Imino ligands 26, 25, and 39, which were obtained from monoacyl- 22 and diacyldihydroxy[2.2]paracyclophanes 21, 38, are tested as chiral ligands in stereoselective Et2Zn addition to benzaldehyde producing 1-phenylpropanol with ee values up to 76%.
