301. A new method for the preparation of 9 : 10-disubstituted anthracenes

Abstract

dihydroxyanthracenes, obtained by the action of Grignard reagents upon anthraquinone, can be conveniently reduced by phenylhydrazine in acetic acid to 9 : 10-disubstituted anthracenes in good yield. 9 : ~~-DI-(~-CARBOXYALI<YL)ANTHRACENES were required for attempted acyloin ringclosures of their dimethyl esters (I; n >3), and the consequent production of bridges across the 9 : 10-positions of anthracene ( 11), but no general method for the synthesis of such acids has been published.The reaction of 9 : 10-dihydro-9 : 10-disodioanthracene with a-halogeno-esters failed to produce any hydrolysable material, possibly because of acylation of the disodio-compound analogous to that reported for ethyl benz0ate.l Clearly, a halide is required which bears on the a-position a relatively inert system which is capable of being converted into a carboxy-group. Ally1 bromide has been employed successfully to give a 35% yield of 9 : 10-diallyl-9 : 10-dihydroanthracene. However, oxidation of this compound to 9 : 10-diallylanthracene, by the use of benzoquinone or chloranil, gave only very poor yields.Accordingly, Grignard reagents bearing a-olefinic and a-ethereal groups, capable of further reaction, have been examined for activity towards anthraquinone, and a study made of the reduction of the 9 : 10-disubstituted 9 : 10-dihydro-9 : 10-dihydroxyanthracenes so obtained. The method of Cook et aL2 for the reaction of anthraquinone with twice the calculated quantity of Grignard reagents gave reproducible yields of the desired diols. Hitherto, the most generally successful reduction of such diols has been to shake their dimethyl ethers with an alkali metal for several days.3 This method failed with 9 : 10-diallyl-9 : 10-diethoxy-9 : 10-dihydroanthracene, potassium or sodium being used, but it was found that such diols, or their ethereal derivatives, could be reduced smoothly by phenylhydrazine in acetic acid in 8 hr. The yields of 9 : 10-disubstituted anthracenes (111) from diprimary alkylanthracenediols are of the order of 60%. 9 : 10-Diallyl-9 : 10-dihydro-9 : 10-dihydroxyanthracene, prepared by Cook et aL2 in unquoted yield, was obtained in 73% yield from allylmagnesium bromide, and found to exist in two isomeric forms, which were easily separated after methylation or ethylation. Both diethyl derivatives absorb at 10.09 p and 10-95 p (allyl), and at 9.4 p (ethoxy). The mixture of diallylanthracenediols, and both dimethyl and diethyl ethers, reacted with phenylhydrazine in acetic acid to give a 65%. yield of 9 : 10-diallylanthracene, absorbing at 10.09 p and 10-95 p (allyl), and identical with the product obtained from 9 : 10-dihydro-9 : 10-disodioanthracene. The best results were obtained by mixing the reactants in the cold, warming the solution rapidly until nitrogen was evolved, and finally refluxing for 4 hr. Addition of the diol to a boiling solution of phenylhydrazine in acetic acid lowered the yield to 31%, and the major product was a yelIow powder, m. p. 195"; the spectral and

Oxygen scavengers and sensitizers for reduced oxygen inhibition in radical photopolymerization

“…The double bond conversion (DBC) and rate of polymerization (R p ) were determined as previously described. 20 RESULTS AND DISCUSSION Synthesis 9,10-Disubstituted anthracene derivatives can be synthesized by conversion of anthraquinone with organometallic reagents 21 and subsequent reductive dehydration with tin dichloride 22 in concentrated hydrochloric acid. Therefore, 9,10-dibutylanthracene (1) was synthesized in an optimized procedure by conversion of anthraquinone with nbutyllithium in 36% yield without isolation of the intermediate 9,10-dibutyl-9,10-dihydro-anthracene-9,10-diol (Scheme 4).…”

Photoinduced processes in macrocyclic isoalloxazine–anthracene systems

“…FL6 was prepared by simple alkylation with 6-bromohexane of 10-hexyl-8-hydroxyisoalloxazine and A4 and A6 were obtained by reduction of the parent 1,5-bis(n-bromoalkoxy)anthraquinones by alkylation and reduction with phenylhydrazine [56].…”