ChemInform Abstract: Scandium(III) Triflate‐Catalyzed Friedel—Crafts Alkylation Reactions.

Abstract

Scandium(III) Triflate-Catalyzed Friedel-Crafts Alkylation Reactions.-The Sc(OTf) 3 -catalyzed Friedel-Crafts alkylation of aromatics (II) with an alcohol, arenecarboxaldehyde or its acetal as the alkylating agents affords diarylmethanes or allylbenzenes in high selectivity, whereby Sc(OTf) 3 is recycled. -(TSUCHIMOTO, T.; TOBITA, K.; HIYAMA, T.; FUKUZAWA, S.; J. Org. Chem. 62 (1997) 20, 6997-7005; Dep. Appl. Chem., Fac. Sci. Eng., Chuo Univ., Bunkyo, Tokyo 112, Japan; EN)

Conversion of Aryl Aldehydes to Benzyl Iodides and Diarylmethanes by H3PO3/I2

“…Among the reported methods, reductive benzylation of arenes using aromatic aldehydes is an attractive protocol to access these compounds. 8,9 Although the reactions have been extensively studied, the following shortcomings remain: (1) expensive or hazardous reductants such as silicohydrides, 10,11 sodium borohydride, 12 and hydrazine 13 are required; (2) metal Lewis acids such as Fe, 10,11 Al, 14 Sc, 15,16 and In 17 are usually required (Scheme 1b). Thus, the development of cheap, green, and metal-free methods for the synthesis of benzyl iodides and diarylmethanes is highly desirable.…”

Cascade Reductive Friedel–Crafts Alkylation Catalyzed by Robust Iridium(III) Hydride Complexes Containing a Protic Triazolylidene Ligand

“…49,50 Cascade direct hydrogenation/Friedel−Crafts alkylation reaction as an efficient method for the functionalization of arenes has not been explored yet, although reductive Friedel− Crafts alkylation has a few precedents (Scheme 1). 42,51,52 Tsuchimoto et al used benzaldehydes and 1,3-propanediol in the presence of 10 mol % Sc(OTf) 3 to form a reactive acetal as the alkylating agent. 51 Using an NHC−Ir complex and 2propanol as a reducing agent, Prades et al expanded the substrates to benzophenone.…”

“…42,51,52 Tsuchimoto et al used benzaldehydes and 1,3-propanediol in the presence of 10 mol % Sc(OTf) 3 to form a reactive acetal as the alkylating agent. 51 Using an NHC−Ir complex and 2propanol as a reducing agent, Prades et al expanded the substrates to benzophenone. 42 Finally, Savela et al reported an iron-catalyzed Friedel−Crafts alkylation with ketones and aldehydes mediated by organosilanes.…”

Palladium-Catalyzed para-Selective Allylation of 1-(Cyanomethyl)arenes with Allyl Acetates

“…1 The conventional Friedel−Crafts allylation of arene nucleophiles with allyl electrophiles is optimized for electronrich arenes (Figure 1A). 2 Despite decades of incremental advances, recent efforts to extend this technology to the selective C−H allylation of electronically neutral arenes, such as alkylbenzenes, retain various limitations, including narrow substrate scopes featuring poor regioselectivities, excesses of arene to avoid overalkylation, and strongly acidic reaction conditions 3 or exclusively intramolecular reactions. 4 Meanwhile, the dearomative allylation of aromatic C−H bonds for benzyl electrophiles is well-studied.…”