Innovative Catalytic Protocols for the Ring‐Closing Friedel–Crafts‐Type Alkylation and Alkenylation of Arenes

Abstract

Over the past years an astonishing number of highly chemoand regioselective intramolecular Friedel-Crafts (IMFC)-type alkylations of aromatic compounds have been described in the literature that allow remarkable synthetic shortcuts for the preparation of challenging aromatic compounds. In particular, both transition metal and conventional and unusual Lewis acids (LAs) have been described to promote ring-clos- Index

Enantioselective Platinum‐Catalyzed Tandem Hydroarylation– Cycloisomerization of 1,6‐Enynes

“…[7] In the latter case, the diastereoselective tandem hydroarylation/cyclization of 1,6-enynes catalyzed by cationic Au(I) species offers the opportunity to create two carbon-carbon bonds and introduce an aromatic ring [8] in a very selective manner related to the Friedel-Crafts reaction. [9] Considering the large occurrence of natural products containing five-membered rings found throughout the chemical literature …”

Ligand‐Free Silver(I)‐Catalyzed Intramolecular Friedel–Crafts Alkylation of Arenes with Allylic Alcohols

“…[2] Friedel-Crafts (FC) alkylation is probably the most reliable and powerful protocol for the elaboration of aromatic rings [3] and over the last few years, a great deal of attention has been devoted toward the design and development of new catalytic protocols with the aim of minimizing hazardous waste production. [4] In this context, metal-catalyzed intramolecular allylic alkylations [5] deserve particular attention as they enable the creation of benzylic stereocenters in functionalized polycyclic aromatic compounds. Although several catalytic aromatic alkylations, employing allyl carbonates/acetates [6] and halides, [7] have been reported, the new frontier in the catalytic allylic alkylation of arenes concerns the use of allyllic alcohols as electrophilic partners.…”

Highly Efficient Molybdenum(II)‐Catalyzed Intramolecular Allylic Alkylation of Arenes

“…In contrast, disappointing results in terms of conversion were recorded with a cationic Mo(IV) complex (i.e., [MoA C H T U N G T R E N N U N G (acac) 2 Cl 2 ]/AgOTf), that was previously described as being active in the alkylation of electronrich arenes with allyl and cinnamyl alcohols (yield 26%, entry 8). [13] The utility of [Mo(CO) 4 Br 2 ] 2 for the synthesis of a variety of substituted tetrahydronaphthalenes was then established and a collection of results is summarized in Table 2.…”

“…Among the plethora of electrophilic precursors employed for the alkylation of aromatic systems, the use of tethered C=C double bonds, bearing a leaving group in the allylic position (allylic alkylation), is of remarkable synthetic interest, providing highly versatile polycylic aromatic compounds. [2,3] For the present, several catalytic allylic alkylation protocols involving heteroaromatics have been described.[4] In contrast, simple benzene derivatives have received much less attention, because of their intrinsic low nucleophilicity with the consequent requirement for harsh reaction conditions as well as stoichiometric amounts of promoting agents.[5]The report by Cook and Hayashi is a breakthrough in this area describing the effectiveness of InCl 3 (10-30 mol%), in the presence of molecular sieves, in catalyzing intramolecular Friedel-Crafts (FC)-type alkylation of arenes via allyl halide activation. [6] In conjunction with our current research interest toward the development of catalytic enantioselective intramolecular allylic alkylation of arenes, [4d] we reasoned that the development of new approaches based on electrophilic transition metal complexes would provide opportunities for developing enantioselective variants of the process.…”