179082-46-3

Upstream product

• 68971-82-4 5,11,17,23,29,35,41,47-octakis(tert-butyl)-49,50,51,52,53,54,55,56-octakis(hydroxy)calix[8]arene 
• 19249-03-7 triethylene glycol di-(p-toluenesulfonate) 

Relevant academic research and scientific papers

Doubly bridged calix[8]crowns

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+.

Singly Bridged Calix[8]crowns

Crowned calix[8]arenes are obtained by direct alkylation of p-tert-butylcalix[8]arene (1) with poly-(ethylene glycol) ditosylates in the presence of various bases. K2CO3 promotes the preferential formation of 1,3-calix[8]crowns. Cs2CO3 mainly gives the 1,5-isomers, which are selectively obtained in high yields when shorter chains are used (1,5-crown-2, 88%; 1,5-crown-3, 78%). NaH affords the 1,4-isomers in yields up to 46%, often as the sole crown derivative, besides unreacted 1. 1,2-Calix-[8] crowns are also obtained in appreciable amount in some instances. The observed regioselectivity is rationalized in terms of preferential formation of specific anions in dependence of the base strength. Dynamic NMR and modeling studies prove that the polyether chain, depending on its bridging mode, may significantly reduce the available space for the through the annulus passages leading to derivatives conformationally blocked (on the NMR time scale).

Regioselective synthesis of calix[8]crowns by direct alkylation of p- tert-butylcalix[8]arene

Direct alkylation of p-tert-butylcalix[8]arene with oligoethylene glycol ditosylates affords calix[8]crowns-n with a bridging pattern dependent on the nature of the base used. Alkali metal hydrides (NaH or KH) afford mainly 1,4- calix[8]crowns 2(n) in yield up to 46%, while K2CO3 and Cs2CO3 with triethylene glycol ditosylate give the 1,3-crown 44 and its 1,5-isomer 54 as the main product, respectively. Appreciable amounts of 1,2-calix[8]crowns 34 are formed with all bases but NaH. At room temperature the 1H NMR spectra of compounds 2(n)-54 show broad signals indicative of hampered conformational mobility.