Selective Synthesis of Poly(m-phenylene oxides) over Oxacalixarenes

Abstract

We report a high yielding AA−BB type step-growth synthesis of poly(m-phenylene oxides) (mPOs) by nucleophilic aromatic substitution (SNAr) reactions. Previously, poly(mPOs) have proven difficult to synthesize, especially by SNAr, due to competing cyclooligomer (oxacalixarene) formation. We have found that the linear (polymeric) vs cyclic (oligomeric) product distribution is strongly dependent on the substitution pattern of the electrophilic monomer, and a model is described that predicts whether the reacting monomers will kinetically favor formation of poly(mPOs) or oxacalixarenes. The polycondensation reaction tolerates a range of functional groups on both reactive monomers, and the synthesized poly(mPOs) have high thermal and aqueous stability but are readily depolymerized in polar aprotic media.

Synthesis, Structure and Conformation of Terphenylene‐Derived Oxacalixaromatics

“…This is possibly a result of the unfavourable conformational preference of the pyrimidine-derived linear ether intermediates in the final ring closure. [13] In the case of heterocycles that possess three aromatic nitrogen atoms, such as cyanuric chloride (8), direct cyclocondensation with 1 did not produce the desired macrocyclic product. Fortunately, by employing a fragment coupling strategy (Scheme 1), the reaction of 1 with 8 in a 1:2 ratio in THF in the presence of diisopropylethylamine (DIPEA) at 0°C afforded the linear terphenyl 14 in 63 % yield, and the subsequent cyclocondensation reaction between 1 and 14 was then accomplished in acetone with DIPEA as base at room temperature to afford dichlorinated oxacalix[2]terphenylene[2]triazine 15 in 33.2 % yield.…”

Straightforward metal-free synthesis of an azacalix[6]arene forming a host–guest complex with fullerene C60

“…4,8 In this case, the experimental conditions are probably responsible of the exclusive formation of the thermodynamically favoured meta-linked azacalix [4]arenes. Interestingly, the importance of using a kinetic vs. thermodynamic control during successive SNAr was illustrated for oxacalixarenes when studying the competing formation of poly(m-phenylene oxides) vs. m-cyclooligomers starting from the condensation of meta-dihydroxyand metadihalido-aryl units 9 which often affords oxacalix[4]arenes rather selectively over other larger macrocycles. 10 Besides the use of non-equilibrating conditions, 11 the synthesis of large moxacalix[n]arenes (n > 4) by convenient SNAr strategies can be achieved following fragment coupling approaches 12 or by introducing bulky groups in the core of the cyclophanes.…”

Synthesis of Inherently Chiral Azacalix[4]arenes and Diazadioxacalix[4]arenes

“…Advances in heteracalixarene synthesis continue to spur active investigation of these compounds as platforms for molecular design and molecular recognition . Our laboratory and others have previously shown that nucleophilic aromatic substitution (S N Ar) reactions are highly efficient for the synthesis of oxacalix[4]arene macrocycles by the condensation of diphenols with a variety of electron-deficient aromatic 1,3-dihalides. The high substrate scope provides access to macrocycles that incorporate two different aromatic monomers (two-component macrocycles) bearing a range of functionality.…”