Not long ago, I sent this article to a fellow-researcher since it might be helpful for his research on Friedel-Crafts techniques. It is
special in this aspect that it uses iodine as catalyst. The published chemical literature contains a handful of potentially (and certainly!) interesting synthesis pathways. For instance, if one could do
Post 361260
(Regis: "Internal aryl alkenes from aryl ketones (WOW!)", Novel Discourse), well, what do you want me to add? Indeed, the actual article...
Acylation of Alkyl Aryl Ethers with Iodine as Catalystby: Xorge Alejandro Dominguez, Beatriz Gomez, J Slim, Dora Giesecke and Ernesto Ureta B
Journal of the American Chemical Society 76 (1954) 5150
Introduction: Acylation with iodine
1,2 as catalyst, gives good yields of some alkoxy-substituted aceto-, propio-, isobutyro- and carprophenones, although the acylation of phenyl acetate, guaiacol, guaiacol acetate and bromo- and iodobenzene is unsuccessfull. We have confirmed the report that anisole does not react with succini anhydrdide in the presence of iodine
3. The preparation of 4-methoxyacetophenone, reported by Chodroff and Klein
3, who used a mole excess of anisole, has been improved.
Our experiments and those of Kaye et al
4, indicate that iodine can be used as a catalyst for the acylation of aromatic ethers by aliphatic or aromatic monocarboxylchlorideds or anhydrides, and that this method is better for the preparation of alkoxy aryl ketones than the conventional Friedel-Crafts procedure. In successful acylation, the violet colored vapors of the refluxing mixture disappeared after 15-30 minutes, but when there was no reaction, the color persisted.
Experimental 5: General procedure, 4-methoxyacetophenone - A mixture of 21.6 g (0.2 mole) of anisole, 22.5 g (0.22 mole) of acetic anhydride and 1.0 g (0.004 mole) of iodine was refluxed for three hours. The dark brown solution was poured into 100 mL of water. The mixture was extracted with ether; the ether solution was washed successively with dilute sodium carbonate, sodium bisulfite and water and then dried over sodium sulfate. After removal of the solvent and distillation of the residue under vacuum, 24 g (80%) of 4-methoxyacetophenone was obtained, bp 120-125° (5 mmHg). The yield was 50% when acetyl chloride was used. After crystallization from aqueous methanol, the compound melted at 37-38° and its semicarbazone at 197-198°; reported mp 38°, semicarbazone at 198-198.5°
3. In the presence of 0.8 g (0.00278 mole), 1.2 g (0.0047 mole), 1.6 g (0.0063 mole), 0.2 g ( 0.00079 mole) of iodine, a mixture of 0.2 mole anisole and 0.22 mole acetic anhydride, gave yields of 68.7, 66, 61.2 and 45% respectively.
2-Methoxy-1-acetylnaphthalene - A mixture of 15.8 g (0.1 mole) of 2-methoxynaphtalene, 11.3 g (0.11 mole) of acetic anhydride and 0.5 g (0.00196 mole) of iodine gave after recrystallization from dilute alcohol, 13.2 g (63%) of 2-methoxy-1-acetylnaphthalene, mp 57°; its mixed mp with an authentic specimen was 57-58°; reported by Noller ans Adams, 57-58°
5.
Y
|
C==O
|
C
/ \
C C--R"
| |
| |
C C--R'
\ /
C
|
R
R R' R" Y Yield mp°
----------------------------------------------
CH3O CH3O H methyl 66.5 47-48
CH3O H CH3O methyl 71 42-43.5
CH3O H H methyl 66 36-37.5
CH3O H H ethyl 50 26-27
CH3O CH3O H ethyl 46.5 56-58
C2H5O H H ethyl 57 29-30
CH3O H H propyl 68 19-21
CH3O CH3O H propyl 74 59-61
CH3O H H i-propyl 42
CH3O H H penyl 49.3 38-39
Acknowledgment: We express our appreciation to Ings Carlos Lopez, Carlos Duhne and Elliot Camarena for their interest and invaluable collaboration and to Amelia Saldana and Ernesto Alatorre for their assistance - Laboratorio de Quimica Organica, Instituto Tecnologico y de Estudios Superiores de Monterrey. Monterrey, NL, MEXICO
References:
1. HD Hartough and AI Kosak, JACS 68 (1946) 2639
2. AI Kosak and HD Hartough, JACS 69 (1947) 3144
3. S Chodroff and HC Klein, JACS 70 (1948) 1647
4. IA Kaye, HC Klein and WJ Burlant, JACS 75 (1953) 745
5. *the melting points are uncorrected*
6. CR Noller and R Adams, JACS 46 (1924) 1889