Efficient Fragment Coupling Approaches toward Large Oxacalix[n]arenes (n = 6, 8)

Abstract

The first rational, stepwise synthesis of enlarged oxacalix[n]arenes (n > 4) is described. Variously substituted oxacalix[3]arene[3]pyrimidines were prepared rather selectively by a straightforward [3 + 3] fragment coupling approach after a thorough search for the optimum nucleophilic aromatic substitution conditions. Similar procedures also allowed facile synthesis of unsymmetrical oxacalix[4]- and oxacalix[8]arenes.

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.…”

Synthetic, Structural, and Photophysical Exploration of meso‐Pyrimidinyl‐Substituted AB2‐Corroles

“…[7] However, recent breakthroughs on the (reductive) demetalation of Cu-and Mn-corroles allow the use of a metalation/demetalation sequence as a protection/deprotection strategy towards elaborated Fb-corroles. [8,9] Within one of our research groups, we have been studying the synthesis and reactivity of 4,6-dichloropyrimidines as versatile structural building blocks for meso-pyrimidinylsubstituted porphyrins, [10] heteracalix [m]arene [m]pyrimidines, [11] and pyrimidine-based (porphyrin) dendrimers. [12,13] During the course of our studies on pyrimidinylporphyrins, it was discovered that a slight modification of the reaction conditions, as optimized for porphyrins, results in the formation of either expanded (penta-and hexaphyrins) [14] or contracted [15] porphyrin analogues.…”

Synthetic Exploration of Oxacalix[2]arene[2]quinazolines

“…Because previous experiments with dichloropyrimidine‐based tri‐ and pentaaryl fragments have afforded good selectivity for enlarged oxacalix[ m ]arene[ m ]pyrimidines ( m = 3, 4),8w the macrocyclization conditions showing the most kinetic control (1,4‐dioxane, K 2 CO 3 , 18‐crown‐6, reflux, simultaneous addition of the precursors) and only limited conversion to the thermodynamic oxacalix[4]arene sink were also tested for dichloroquinazolines. Notably, the one‐pot synthesis approach under these conditions resulted in an inversion of the regioisomeric ratio.…”

“…To date, most reports on oxacalixarenes describe the synthesis of oxacalix[4]arenes through facile nucleophilic aromatic substitution (S N Ar) strategies employing variously substituted m ‐dihydroxybenzenes and activated arenes, either 1,5‐difluoro‐2,4‐dinitrobenzene or electrophilic m ‐dihalogenated heteroaromatic analogues (e.g., 1,3,5‐triazines or pyridines) 7,8. Previous work within our group has focused on the synthesis of oxacalix[ m ]arene[ m ]pyrimidines ( m = 2–6) through S N Ar reactions of resorcinol derivatives and 4,6‐dihalopyrimidines 8f,8p,8w. It has been demonstrated that oxacalix[ m ]arene[ m ]pyrimidines, due to their high‐yielding synthesis, tunable macrocycle size, and ease of elaboration of the substitution pattern, are versatile oxacalixarene platforms for the exploration of various supramolecular applications 7,10…”