Calixnaphthalenes: Deep, Electron-Rich Naphthalene Ring-Containing Calixarenes. The First Decade

Abstract The first naphthalene ring-based analogues of the better-known and extensively studied calixarenes were synthesized in 1993. Since that time, our group has focused its research on the design and synthesis of other ‘calixnaphthalenes’. These endeavours are motivated partly due to the synthetic challenges which they provide, and to the challenges in deciphering their structural and complexation properties. Calixnaphthalenes offer several advantages over their calixarene analogues. Among these are the facts that they can form deeper, more electron-rich and in some cases, chiral, cavities. They also provide a wide range of potential new scaffolds upon which to design and build new receptors for neutral, or charged guest species. Their supramolecular complexation properties have barely been explored as yet since in most cases, only relatively small quantities only of these compounds have been obtained. In this review, all of the known, and previously unreported calixnaphthalenes are described. As well, some of the compounds, which are described, are still subjects of ongoing research. 1 Introduction 2 EXO-calix[4]naphthalenes Derived from 1-Naphthol 3 EXO-calix[4]naphthalenes Derived from 1,8-Naphthalenesultone 4 ENDO-calix[4]naphthalenes Derived from 2-Naphthol 4.1 C 4 -Symmetrical ENDO-calix[4]naphthalenes 4.2 Ethoxycarbonylmethoxy Esters Derived from 7 and 16 4.3 Alkyl Ethers Derived from 7 and 16 4.4 Spiro- and Bis(spirodienone) Derivatives of 7 and 16 4.5 C 2 -Symmetrical ENDO-calix[4]naphthalenes 4.6 C 2 -Symmetrical ‘ENDO-EXO’-calix[4]naphthalenes 5 ENDO-isocalix[4]naphthalenes Derived from 2,3-Dihydroxynaphthalene 6 ‘Expanded’ Calix[4]naphthalenes 7 Other Naphthalene-Containing Calixarenes 8 Dihomocalix[4]naphthalenes 9 Hexahomotrioxacalix[3]naphthalenes 10 Lower-Rim Functionalized Hexahomotrioxacalix[3]naphthalenes 11 Tetrahomodioxacalix[4]naphthalenes 12 Hexahomodioxacalix[4]naphthalenes 13 Octahomotetraoxaisocalix[4]naphthalenes 14 Conclusions