Friedel-Crafts reactions indium triflate

Indium trichloride349-351 is a mild Lewis acid that is effective for various kinds of Lewis-acid-catalyzed reactions such as Diels-Alder reactions (Scheme 85), aldol reactions, and Friedel Crafts reactions. Since indium trichloride is stable in water, several aqueous reactions have been investigated (Scheme 85) indium(III) triflate is also used as a Lewis acid. 

Indium(III) chloride and indium(III) triflate have been introduced to organic syntheses as versahle Lewis acids. They are stable in water, and catalyze a variety of organic reachons, e.g. the Diels-Alder reaction, the aldol reaction, Michael addi-hon, the Friedel-Crafts reaction, and other organic transformations. 

There has been a review of asymmetric Friedel—Crafts reactions. It has been shown that the rhodium-catalysed reaction of potassium phenyltrifluoroborate with A-tosyl ketimines may lead to products such as (18) with high enantioselectivity. (g) The reaction of A-t-butanesuUinylimino esters with arenes to give products (19) is catalysed by Lewis acids, such as indium triflate, and may lead to enantio-metrically enriched a-glycines. The intramolecular alkylation of hydrogenated 0 tetralins, shown in Scheme 2, using iron(III) or aluminium(III) catalysts yields cis-hexahydrobenzophenanthridines. Formation of a stabilized carbocation intermediate is... 

Indium(in) triflate (1 mol %) is an excellent catalyst for the Friedel-Crafts acylation reaction. The addition of 1 equiv of lithium perchlorate to the reaction mixture markedly accelerates the reaction. Thus, under mild conditions, anisole is acylated to give the product in excellent yields (eq 3). Acetic anhydride, acetyl chloride, and isopropenyl acetate can he used as acyl donors. 

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