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Friedel–Crafts alkylations can be reversible. Although this is usually undesirable it can be exploited; for instance by facilitating transalkylation reactions. [10] 1,3-Diisopropylbenzene is produced via transalkylation, a special form of Friedel–Crafts alkylation. It also allows alkyl chains to be added reversibly as protecting groups.
Clemmensen reduction conditions are particularly effective at reducing aryl [4]-alkyl ketones, [5] [6] such as those formed in a Friedel-Crafts acylation. The two-step sequence of Friedel-Crafts acylation followed by Clemmensen reduction constitutes a classical strategy for the primary alkylation of arenes .
In Friedel-Crafts alkylations, the normal halogen leaving group order is reversed so that the rate of the reaction follows RF > RCl > RBr > RI. This effect is due to their greater ability to complex the Lewis acid catalyst, and the actual group that leaves is an "ate" complex between the Lewis acid and the departing leaving group. [ 6 ]
James Crafts, the son of Royal Altamont Crafts and Marianne Mason (daughter of Senator Jeremiah Mason), [3] [4] was born in Boston, Massachusetts and graduated from Harvard University in 1858. Although he never received his Ph.D. , he studied chemistry in Germany at the Academy of Mines (1859) of Freiberg , and served as an assistant to Robert ...
Freund reaction; Friedel–Crafts acylation; Friedel–Crafts alkylation; Friedländer synthesis; Fries rearrangement; Fritsch–Buttenberg–Wiechell rearrangement; Fujimoto–Belleau reaction; Fujiwara–Moritani reaction; Fukuyama coupling; Fukuyama indole synthesis; Fukuyama reduction
The reaction is a type of Friedel-Crafts acylation with hydrogen chloride and a Lewis acid catalyst. The synthesis of 2,4,6-Trihydroxyacetophenone (THAP) from phloroglucinol is representative: [1] If two-equivalents are added, 2,4-Diacetylphloroglucinol is the product. Hoesch reaction example, 1-(2,4,6-trihydroxyphenyl)ethanone from phloroglucinol
Phenethyl alcohol is prepared commercially via two routes. Most common is the Friedel-Crafts reaction between benzene and ethylene oxide in the presence of aluminium trichloride. C 6 H 6 + CH 2 CH 2 O + AlCl 3 → C 6 H 5 CH 2 CH 2 OAlCl 2 + HCl. The reaction affords the aluminium alkoxide that is subsequently hydrolyzed to the desired product.
In addition to the ordinary thermal phenyl ester reaction a photochemical variant is possible. The photo-Fries rearrangement can likewise give [1,3] and [1,5] products, [7] [8] which involves a radical reaction mechanism. This reaction is also possible with deactivating substituents on the aromatic group. Because the yields are low this ...