Dibenzofuran. IX. Metalation of Some Derivatives

Abstract

Metalation of Some Dibenzofuran Derivatives 951 these data are not quite in agreement with those given in the literature for 4,5-benzpyrene6 (m. p. 178-179°, picrate 229-230°), we believe that the structure is correct.peri-Naphthindone from -Naphthol.-a-Naphthol (72 g.) and acrolein (56 g.) were added simultaneously, within forty minutes, to anhydrous hydrofluoric acid (530 g.) at 15-20°. A sample of the condensation mass soon showed the bright green fluorescence in sulfuric acid, characteristic for ¿>m'-naphthmdone.A precipitate formed in the hydrofluoric acid, while the reaction mass was agitated overnight. The condensation mass was poured onto ice, and the suspension filtered and washed. A brown powder (105 g.) was obtained, which was soluble in sulfuric acid with a yellow color and a strong green fluorescence. Fifty grams of this product was extracted with 500 cc. of boiling dichlorobenzene. The solvent extract was steam distilled to remove the solvent, peri-Naphthindone crystallized from the water layer (4000 cc.) in light yellow crystals. Much tarry matter also was obtained. The pm'-naphthindone was identified by its melting point (151°), mixed melting point with a sample prepared according to German Patent 283,066, by its color and fluorescence in sulfuric acid. Similarly, perinaphthindone was obtained from /3-naphthol.Condensation of Acenaphthene with Acrolein.-Acrolein (28 g.) and acenaphthene (30.8 g.) were added to an-(5) J. W. Cook, C. L. Hewett and I. Hieger, J. Chevt. Soc., 395 (1933).hydrous hydrofluoric acid (370 g.) at 15-18°in ten minutes, and this solution was agitated for one hour at 10-15°. Acenaphthene showed no coloration in sulfuric acid, but the condensation product which formed as soon as acrolein was added dissolved in sulfuric acid with a brilliant green color. A finely divided precipitate formed while the charge was agitated at 15-20°for one hour. The reaction product isolated (51 g., light brown powder) after decomposition with ice had no melting point, dissolved in sulfuric acid with brilliant green color, and was only sparingly soluble in organic solvents with yellow color, and without appreciable fluorescence. A low melting product was isolated by extraction in a Soxhlet apparatus but could not be crystallized or identified. Summary "Peri" condensations which are not possible in sulfuric acid were performed in anhydrous hydrofluoric acid. "Peri" condensations obtained in sulfuric acid also could be performed in hydrofluoric acid. Perylene was obtained from phenanthrene and l,10-trimethylene-9-hydroxyphenanthrene, 4,5-benzpyrene from 9,10-dihydroanthracene, and pen-naphthindone from a-and /3-naphthol. Wilmington, Del.

Unravelling Factors Affecting Directed Lithiation of Acylamino­aromatics

“…For example, lithiation of 2-bromodibenzofuran (11) with n-BuLi initially undergoes halogen-metal exchange to give 2-lithiodibenzofuran (12), which then lithiates unreacted 2-bromodibenzofuran to give 2-bromo-4-lithiodibenzofuran (13) along with dibenzofuran (14; Scheme 4), as inferred from the structure of the carboxylation product obtained. 22,23 Despite the electronegativity of oxygen and nitrogen atoms, lithiation at a carbon atom attached to an NMe 2 or OMe group is disfavored as a result of the destabilizing interaction of the lone pairs of electrons on N or O with the electrons of the C-Li bond (Figure 3). However, such α-lithiation may be favored when the lone pairs are delocalized by conjugation with a carbonyl group, which reduces the repulsive interaction and provides an attractive interaction between the Li and O atoms ( Figure 3).…”

Synthese und eigenschaften von oxydo‐p‐oligophenylenen. 18. Mitteilung über poly‐ und oligophenylene

“…Die Gewinnung des fur die Systematik wichtigen Dioxydo-p-terphenyls XL wurde daraufhin nach einem von GRAEBE und U L L M A N N~~) entwickelten Syntheseprinzip (17) versucht, das die COMBERG-Reaktion benutzt. Auf die enge Beziehung zur PSCHORRschen Phenanthren-RingschluGreaktion25t26) braucht kaum hingewiesen zu werden.…”

“…Die Gewinnung des fur die Systematik wichtigen Dioxydo-p-terphenyls XL wurde daraufhin nach einem von GRAEBE und U L L M A N N~~) entwickelten Syntheseprinzip (17)…”

Rapid Access to Bi‐ and Tri‐Functionalized Dibenzofurans and their Application in Selective Suzuki–Miyaura Cross Coupling Reactions

“…In the 1930s to 1950s, Gilman and co‐workers described various substitution patterns and trends in reactivity and selectivity for functionalization of dibenzofuran motifs. In general, 4‐, 6‐ or 4,6‐substituted dibenzofurans are accessible via metalation of dibenzofuran followed by reaction with an electrophile . Halogenation and sulfonation are reported to address the 2‐position, while nitration allows for functionalization of the 3‐position.…”

“…Halogenation and sulfonation are reported to address the 2‐position, while nitration allows for functionalization of the 3‐position. [7c] However, in most cases the reported yields of purified products are below 40 %, limiting the use in preparative organic chemistry. Moreover, double halogenation occurred frequently for some derivatives, showing a lack of regioselectivity .…”