Modified Ullmann Reaction Research Articles

Modified Ullmann coupling of 2-chloro-3-trifluoromethylpyridine

The application of the modified Ullmann reaction to 2-chloro-3-trifluoromethylpyridine furnishes 5,5′-bis(trifluoromethyl)-2,2′-bipyridine as the primary product, accompanied by small amounts of the expected 3,3′-bis(trifluoromethyl)-2,2′-bipyridine, 2-benzyl-3-(trifluoromethyl)pyridine, bibenzyl, 3-trifluoromethylpyridine, 3-methylpyridine, 2-hydroxyethyl-(3-trifluoromethylpyridyl) ether and 2-hydroxyethyl-(3-methylpyridyl) ether. For comparison purposes, a sample of 3,3′-bis-(trifluoromethyl)-2,2′-bipyridyl was prepared by the treatment of 2,2′-bipyridyl-3,3′-dicarboxylic acid with sulfur tetrafluoride. The formation of all but two compounds mentioned above can be rationalized on the basis of the single-electron-transfer process.

Structural analysis and electrical properties of halogen substituted poly(paraphenylene)

AbstractPoly(tetrafluoro‐p‐phenylene) was prepared by the modified Ullmann reaction. The average degree of polymerization was determined from electron impact mass spectrometry and was found to be n = 8. The structure of the polymer was studied using infrared, Raman, ultraviolet absorption spectroscopy and differential scanning calorimetry. Polymerization of 1,4‐diiodo‐2,3,5,6‐tetrafluorobenzene resulted in the disappearance of the characteristic C‐I vibrations and the appearance of new absorption bands in the infrared and Raman spectra. At room temperature poly(tetrafluorophenylene) is an insulator. Attempts to increase the dc conductivity on FeCl3 and sodium doping were unsuccessful until now.

Preparation of new dihydrofuro[2,3‐f]indole derivatives

AbstractThe preparation of new dihydrofuro[2, 3‐f]indole derivatives and their fully aromatic counterparts is described. Key steps in the synthesis include a Claisen rearrangement/m‐chloroperoxybenzoic acid oxidation sequence to form a dihydrobenzofuran intermediate and an iron/acetic acid reductive cyclization to generate the dihydrofuro[2, 3‐f]indole nucleus. Introduction of a 5‐phenyl substituent on the indole nitrogen was effected by a modified Ullmann reaction. Fully aromatic furo[2, 3‐f]indoles were obtained from the dihydro congeners by dehydrogenation with 2, 3‐dichloro‐5, 6‐dicyano‐1, 4‐benzoquinone.

Syntheses totales et etudes de lignanes biologiquement actifs. application de l'α-hydroxyalkylation de β-benzyl γ-butyrolactones a la creation des squelettes phenyl tetraline et bisbenzocyclooctadiene—4 : Synthese totale de la (±)-steganone et de ses congeneres, et synthese du (±)-stegane

The biphenyl 16 (obtained from α-bromopiperonal and the aromatic iodide 14 by a modified Ullmann reaction) was cyclized by intramolecular hydroxyalkylation to the isomeric alcohols 17a and 17b. These were oxidized using Jones' reagent, to afford the enol 18a, together with the tautomeric β-ketolactone Decarboxylation of this mixture using barium hydroxide, followed by Jones' oxidation gave the isomeric γ-ketoacids 11a and 11b. These were converted to (±)-steganone 1 using Raphael's method, in an overall yield of ca 10% starting from 3, 4, 5-trimethoxybenzaldehyde, and in 20,7% yield, starting from the biphenyl 16.

A total synthesis of (±) steganacin via the modified Ullmann reaction

A total synthesis of (±) steganacin via the modified Ullmann reaction

Bisbenzylisoquinoline Alkaloids and Related Compounds. IX. A Modified Total Synthesis of Stereoisomeric Mixture of Magnolamine : Studies on the Syntheses of Heterocyclic Compounds. CXLV.

O-Benzylmagnolamine (XXI) was successfully obtained by the modified Ullmann reaction of dl-7-benzyloxy-1-(4, 5-bisbenzyloxy-2-bromobenzyl)-1, 2, 3, 4-tetrahydro-6-methoxy-2-methylisoquinoline (III) with 7-benzyloxy-1-(4-hydroxybenzyl)-1, 2, 3, 4-tetrahydro-6-methoxy-2-methylisoquinoline (IV) without any detectable side reaction in thin-layer chromatography. Since removal of benzyl group by hydrolysis had already afforded magnolamine (I), a modified total synthesis of stereoisomeric mixture of magnolamine has been accomplished.

Bisbenzylisoquinoline alkaloids and related compounds. V. A total synthesis of diastereoisomeric mixture of liensinine.

Diastereoisomeric mixture of O, O-dibenzyl-liensinine (II) was successfully obtained by the modified Ullmann reaction of dl-1-(4-benzyloxybenzyl)-2-methyl-6-methoxy-7-hydrozy-1, 2, 3, 4-tetrahydroisoquinoline (XVII) with dl-1-(3-bromo-4-benzyloxybenzyl)-2-methyl-6, 7-dimethoxy-1, 2, 3, 4-tetrahydroisoquinoline (X) which has a large substituent such as benzyloxy-group at the ortho position of bromobenzene nucleus, without any detectable side reaction on the thin-layer chromatography. Removal of benzyl group by treating II with hydrochloric acid gave diastereoisomeric mixture of liensinine (I'), whose infrared and ultraviolet spectra were identical with those of natural product.