Upper-rim calixarene phosphines consisting of multiple lower-rim OH functional groups: synthesis and characterisation

Abstract

The synthetic approaches to mono-isopropoxytrihydroxycalix[4]arenes bearing two or three diphenylphosphino groups at the upper macrocycle rim were elaborated. Due to reactive hydroxyl groups at the lower rim capable of binding with silica gel surface, the calixarenes, especially the enantiomerically pure inherently chiral diphosphinocalixarene, are promissing ligands for creation of hybride organic -inorganic metallocomplexing catalysts of organic (asymmetric) reactions.

Selected applications of calixarene derivatives

“…The number of reports on calixarenes is enormous, [93][94][95][96][97][98] they show results of theoretical studies, as well as practical applications of these compounds. Therefore an exhaustive presentation of studies dealing with calixarenes would be impossible, and in the review only selected examples are described.…”

Inherently Chiral Calixarenes: Synthesis and Applications

“…These products could be further brominated with N ‐bromosuccinimide (NBS; selective for phenolic rings) and then the sulfonyl group hydrolysed to give pure ICCs 3 which have potential as further building blocks. The authors themselves have reported a bisphosphine ICC 4 derived from this building block, although it is a very preliminary report and no application to asymmetric catalysis has yet been demonstrated …”

“…The authors themselves have reported ab isphosphine ICC 4 derived from this building block, although it is av ery preliminary report and no application to asymmetric catalysis has yet been demonstrated. [17] Boyko andK alchenko have also employed their more robust proximal alkylation strategy [16,19] using the chiral alkylating agent (R or S)-N-(1-phenylethyl)bromoacetamide (6) to generate lower-rim ICCs. [16,20] When alkylating am onopropoxy calix [4]arene, no diastereoselectivity was observed in the products.…”

“…These are attractive targets as they can associate with protonated amines and thus Scheme2.Kalchenko's camphor-sulfonylation route:diastereomers obtained through crystallisation. [15,17] Scheme3.Boyko and Kalchenko's proximal monoalkylation route:d.r. = 2:1, major diastereomer obtained throughcrystallisation.…”

“…The term 'family members' is in itself extremelyb road and can be used to described either the overall size of the calixarene (i.e. number of phenolr ings, which can range from [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] or even other classes of the structurally related molecules, such as the aza-, oxa and thiacalixarenes, not that we should forget the resorcinarenes and other structurally similar compounds.A si ft his is not enough,w ithin each family,d ifferent conformers are also possible:f or example Figure 1shows the four possible conformations of calix [4]arene (note:t he number 4r epresents the four phenol rings). It should therefore be very easy to appreciate the sheer broadness of the field of calixarenes and why many books, and even ac onference series have been dedicated to them.…”