One step facile synthesis of bromo calix[n]arenes

ipso-Bromination of tert-butylcalix[4]arenes

“…In order to introduce the bromine group, the tert-butyl group needs to be removed in a reverse Friedel-Crafts alkylation step with aluminium trichloride (AlCl3) and a sacrificial phenol. 2 There is one report in the literature by Varadarajan and co-workers, 3 however, that describes the direct ipso-bromination of calix [4]-, calix [6]-and calix [8]arenes via their tert-butyl derivatives, which removes a whole synthetic step when pursuing aryl-brominated calixarenes. Whilst this paper has been frequently cited, no citing document has made use of the ipso-bromination method they report.…”

The kinetic product of the octabromination of p-tert-butylcalix[8]arene octamethyl ether

“…This product was also different from the highly symmetric isomer reported in the literature. 25 Examination of a sample of the product in CDCl 3 after standing in the NMR tube for four days at room temperature indicated its complete isomerization into the equilibrium mixture of octabromo isomers. The isomerization of this product was significantly slower in C 6 D 6 .…”

“…21 Bromination of the octamethyl ether of p-tert-butylcalix [8]arene 4 with excess NBS under irradiation has been reported to afford a major octabromo product 8. 25 The NMR spectrum of this product consisted of a very simple pattern of signals (single singlets for the aromatic, methine, methoxy and t-Bu groups). 25 In principle, eighteen isomers are possible for 8 (see Figure 1) resulting from the cis or trans dispositions of the bromines on the bridges.…”

“…25 The NMR spectrum of this product consisted of a very simple pattern of signals (single singlets for the aromatic, methine, methoxy and t-Bu groups). 25 In principle, eighteen isomers are possible for 8 (see Figure 1) resulting from the cis or trans dispositions of the bromines on the bridges. 27 The spectrum reported (assuming fast rotations of the aryl rings on the NMR timescale) indicates a molecule of high symmetry, and is consistent only with the all-cis or all-trans isomers.…”

“…[19][20][21][22][23] These bromo derivatives can be prepared via photochemical bromination of the corresponding calixarene methyl ethers 1-4. [19][20][21][22][24][25][26] The hexabromocalix [6]arene derivative 7 reacts with a variety of O-, N-, and even Cnucleophiles under S N 1 conditions affording a wide array of methylene-functionalized calix [6]arenes derivatives. For example, heating to reflux a mixture of 7, 2,4-pentanedione and hexafluoroisopropanol (HFIP) yields the derivative 9 in a reaction involving sixfold C-C bond formation (Eq.…”