40836-01-9

Safe and inexpensive methods for synthesis of a series of four substituted 2,4,6-triphenylyrylium tosylate salts with different substituents are reported. The synthesis methods use p-toluenesulfonic acid monohydrate instead of conventional acid catalysts

The multifaceted potentialities of expanded pyridiniums (EPs), based on one pyridinium core bearing a 4-pyridyl or 4-pyridylium as the N-pyridinio group, are established at both experimental and theoretical levels. Two classes of head-to-tail (htt) EPs were designed, and their first representative elements were synthesized and fully characterized. The branched (B) family is made up of 2,6-diphenyl-4-aryl-1,4′-bipyridin-1-ium (or 1,1′-diium) species, denoted 1B and 2B for monocationic EPs (with aryl = phenyl and biphenyl, respectively) and 1BMe and 2BMe for related quaternarized dicationic species. The series of fused (F) analogues comprises 9-aryl-benzo[c]benzo[1,2]quinolizino[3,4,5,6-ija][1,6]naphthyridin-15-ium species, denoted 1F and 2F, and their 2,15-diium derivatives referred to as 1FMe and 2FMe. Electrochemistry (in MeCN vs SCE) reveals that branched EPs undergo a single reversible bielectronic reduction at ca. -0.92 V for 1B/2B and -0.59 V for 1BMe/2BMe, whereas pericondensed species show two reversible monoelectronic reductions at ca. -0.83 and -1.59 V for 1F/2F and ca. -0.42 and -1.07 V for 1FMe/2F Me. Regarding electronic absorption features, all htt-EP chromophores show absorptivity in the range of ca. 1-4 × 104 M-1 cm-1, with red-edge absorptions extending toward 450 and 500 nm (in MeCN) for 2BMe and 2FMe, respectively. These lowest-energy pi-pi* transitions are ascribed to intramolecular charge transfer between the electron-releasing biphenyl group and the htt-bipyridinium electron-withdrawing subsystems. EPs display room-temperature photoemission quantum yields ranging from 10% to 50%, with the exception of 1B, and branched luminophores are characterized by larger Stokes shifts (8000-10 000 cm -1) than fused ones. Lastly, a method to predict the efficiency of photobiscyclization of branched EPs into fused ones, based on the analysis of computed difference maps in total electron density for singlet excited states, is proposed.

2,4,6-Triphenylpyrylium chloride is released together with 1,3,5-triphenyl-2,4-dichloro-2-pentene-1,5-dione during the action of chlorine on 1,3,5-triphenyl-2-pentene-1,5-diones under mild conditions.The reaction of 2-pentene-1,5-dione with chlorine in th

In the presence of piperidine acetate (or similar salts of certain dialkylamines), 2,4,6-triarylpyrylium perchlorates 5 react with methyl(ene) ketones 6 to give benzophenones 7, the structure of which was proved by spectroscopic methods as well as by independent synthesis.Besides acetone and other acyclic ketones (e. g. alkyl methyl ketones, phenylacetone, desoxybenzoin, dibenzyl ketone) cyclic ketones (e. g. cyclopentanone, cyclohexanone, cycloheptanone, acenaphthenone) can also be used as ketone component 6; acetophenones react differently leading to hydrocarbons of the 1,3,5-triarylbenzene type 15.The varying efficiency of the diverse amine salts and the mode of incorporation of the unsymmetrically substituted ketones suggest the intermediate formation of enamines 10 as crucial step of the ring transformations observed.This assumption is supported by isolation of the iminium salt 18 on reacting 3,5-dimethyl-2,4,6-triphenylpyrylium perchlorate (16) with acetone/piperidine acetate.