Metal-free synthesis of azacalix[4]arenes

Single‐Step, Regioselective Synthesis of Diazadioxacalix[4]arenes and Diazadioxa[14]cyclophanes Bearing an Alternating N/O‐Bridge Pattern

“…Under optimized conditions (CsF, DMSO, 80 °C, 18 h), 3a was formed as >80 % of the unpurified reaction mixture without detectable amounts of the alternative bridge‐pattern regioisomer. The formation of 3a was most efficient when the reaction was carried out at relatively high concentration (0.25 M with respect to 2a ), which is consistent with related ring formations 3e,5b…”

N‐Substituted Azacalixphyrins: Synthesis, Properties, and Self‐Assembly

“…Therefore, we decided to develop a more versatile and efficient approach based on the introduction of N‐substituents prior to the macrocyclization step. This approach required the synthesis of N‐substituted tetraaminobenzene derivatives 8 a and 8 b (see Scheme and the Supporting Information), for which two NH 2 functions in the meta position were available as nucleophilic partners in S N Ar reactions (Scheme ) . Notably, the presence of additional N‐BOC substituents in 8 a and 8 b prevents their oxidation by air.…”

“…This approachr equired the synthesis of N-substituted tetraaminobenzene derivatives 8a [15] and 8b (see Scheme 2a nd the Supporting Information), for which two NH 2 functionsi nt he meta positionw ere available as nucleophilic partnersi nS N Ar reactions (Scheme 2). [16,17] Notably,t he presence of additional N-BOC substituents in 8a and 8b prevents their oxidation by air.T he condensation reaction between 8a and electron-deficient aryl 7 (1 equiv) in MeCN at reflux for 3h led to am ixture of the [1+ +1] and [1+ +2] adducts (9 a and 10 a)i n1 8a nd 12 %y ield, respectively (Scheme 2). The same reactionc onducted for 3days with 7 (2 equiv) exclusively formed [2+ +1] product 10 a in 28 %y ield (Scheme 2).…”

Semifield testing of a bioremediation tool for atrazine‐contaminated soils: Evaluating the efficacy on soil and aquatic compartments

“…Though cyclopyridines are obvious candidate hosts for cations, the methylene‐bridged cyclopyridine, calix[4]pyridine, does not appear to bind cations 59, 60. In the past decade, hetero‐bridged calixarenes61–64 such as thiacalixarene,65, 66 NH(NMe)‐bridged calixarene,67–76 and oxacalixarene77–88 attracted significant interest as potential cation binders without further functionalization. Although the recognition of cations clearly requires an appropriate conformation of the calixarene, the structural and conformational relationship of the parent and heteroatom‐bridged calix[4]arenes is unclear.…”