Anthracenes, polymer-supported

Another interesting scavenger is polymer-supported anthracene, developed by Porco for the scavenging of dienophiles [109]. An example of its application to the synthesis of a complex 5,8-dihydro-(l,2,4)triazolo[l,2-a]pyridazine-l,3-diones via hetero-Diels-Alder reaction followed by removal of the excess of triazole-3,5-dione under microwave irradiation is depicted in Scheme 24. For this particular example, moving from thermal heating (toluene, 100 °C) to a microwave-assisted protocol (DCE, 150 °C) reduced scavenging time from 3 h to just 15 min. 

Further investigation of this interesting reaction carried out much later by other workers indicated that the photoproduct was not an anthracene polymer but was dimeric in nature. This conclusion was supported by the following data ... 

Rhodium(II) acetate catalyzes C—H insertion, olefin addition, heteroatom-H insertion, and ylide formation of a-diazocarbonyls via a rhodium carbenoid species (144—147). Intramolecular cyclopentane formation via C—H insertion occurs with retention of stereochemistry (143). Chiral rhodium (TT) carboxamides catalyze enantioselective cyclopropanation and intramolecular C—N insertions of CC-diazoketones (148). Other reactions catalyzed by rhodium complexes include double-bond migration (140), hydrogenation of aromatic aldehydes and ketones to hydrocarbons (150), homologation of esters (151), carbonylation of formaldehyde (152) and amines (140), reductive carbonylation of dimethyl ether or methyl acetate to 1,1-diacetoxy ethane (153), decarbonylation of aldehydes (140), water gas shift reaction (69,154), C—C skeletal rearrangements (132,140), oxidation of olefins to ketones (155) and aldehydes (156), and oxidation of substituted anthracenes to anthraquinones (157). Rhodium-catalyzed hydrosilation of olefins, alkynes, carbonyls, alcohols, and imines is facile and may also be accomplished enantioselectively (140). Rhodium complexes are moderately active alkene and alkyne polymerization catalysts (140). In some cases polymer-supported versions of homogeneous rhodium catalysts have improved activity, compared to their homogenous counterparts. This is the case for the conversion of alkenes direcdy to alcohols under oxo conditions by rhodium—amine polymer catalysts... 

In 2004, Porco described the application of a polymer-supported anthracene for the scavenging of excess dienophile from Diels-Alder reactions [48]. This scavenger was not only demonstrated with a range of dienophiles, but also its application was related in the synthesis of flavonoid dienes and other classes of cyclic molecules (Scheme 8.35). 

Scheme 8.35 Scavenging of excess dienophile from Diel-Alder reactions using a polymer-supported anthracene.

The polymer supported magnesium "anthracene suffers from relatively low loading of the active sites and this lead to the development of the silica supported analogues. Scheme 8.12 3(). This approach Uses hwlroxyl depleted silica surfaces... 

There are a few organic semiconducting compounds that contain a significant amount of carbon-carbon bonding and are also capable of supporting electronic conduction. Anthracene and Ziegler-catalyzed acetylene polymers (conjugated polyolefins) are examples. See crystals impurity solid solid-state chemistry. 

Capillaries were then filled with the imprinting mixture containing monomers (0.375 mmol bisphenol A and 0.455 mmol p.p -diisocyanatodiphenylmethane), cross-linkers (0.250 mmol trihydroxybenzene and 0.195 mmol p,o,p -triisocyanato-diphenylmethane, template molecule (0.0485 mmol anthracene), and porogen (DMF). Overnight polymerization under ambient conditions was used to cure the polymer. A quartz plate was placed on top of the PDMS to avoid lift-off of the stamp during polymerization. Once cured, the elastomeric stamps were peeled from the wafer support leaving behind the polymer microstructures. 

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