190844-26-9Relevant academic research and scientific papers
Doubly bridged calix[8]crowns
Geraci, Corrada,Consoli, Grazia M. L.,Piattelli, Mario,Neri, Placido
, p. 1345 - 1361 (2007/10/03)
Biscrowned calix[8]arenes were obtained by alkylation of p-tert-butylcalix[8]arene or calix[8]monocrowns with triethylene glycol ditosylate, in the presence of various bases. Of the 22 possible isomers, 1,4:2,5-, 1,3:2,5-, 1,4:2,3-, 1,4:5,8-, and 1,2:3,4-calix[8]biscrown-4 (3-7) were isolated in 7-30% yields. The presence of two crown bridges in 1,3:2,5- and 1,4:2,5-biscrown-4 (4, 5) leads to a significant rigidness of the calix[8]arene macrocycle and implies inherent chirality. The increased preorganization of calix[8]biscrowns, with respect to monocrowns, leads to significant complexing abilities for alkali cations with a marked preference for Cs+ over Na+.
Inherent chirality in calix[8]arenes exploiting the steric constraint of two intercrossing polyether chains
Geraci, Corrada,Piattelli, Mario,Neri, Placido
, p. 7627 - 7630 (2007/10/03)
The first example of covalently linked, inherently chiral calix[8]arene, 1,4-2,5-calix[8]bis-crown-4 3, has been obtained from either 1,4-calix[8]crown-4 1 or p-tert-butylcalix[8]arene by alkylation with triethylene glycol ditosylate. The inherent chirality of 3, due to the steric constraint of the two intercrossing crown bridges, is evidenced by signal splitting in the 1H NMR spectrum after addition of Pirkle's reagent.
