Allyl- and Benzylindium Reagents. Carboindation of Carbon−Carbon and Carbon−Nitrogen Triple Bonds

Abstract

The reaction of unactivated simple terminal alkynes 1 with allylindiums in THF proceeded smoothly to give the corresponding allylation products 2 in good to high yields. This result is in marked contrast to that of the reaction carried out in DMF, where the allylation of unactivated alkynes was very sluggish. The allylic group of the reagent was attached to the internal carbon of the triple bond, and indium was attached to the less substituted terminal carbon, except for the case of TMS substituted acetylenes 1j and 1k in which the allyl group went to the less substituted carbon of the triple bond. The reaction of unactivated simple terminal and certain internal acetylenes with benzylindium in THF proceeded smoothly to afford the corresponding benzylation products 18 in good to high yields. The benzyl group was attached to the less substituted unhindered carbon of the triple bond, and indium was attached to the more sterically congested carbon. The reaction of activated nitriles 3 with allylindiums in THF at 70 °C gave the corresponding allylation−enamination products 4 in high to excellent yields. This reaction provides a useful method for the synthesis of highly functionalized enamines, which are not easily available via conventional methods. The mechanisms on the above three indation reactions are discussed.

Direct Synthesis of Water‐Tolerant Alkyl Indium Reagents and Their Application in Palladium‐Catalyzed Couplings with Aryl Halides

“…Among the many organoindium compounds, allylic indium reagent has been extensively studied by Araki, Chan, Li, Lloyd‐Jones, our group, and others 7. In recent years, Knochel,2, 3 Minehan,4 Chupak,5 Yamamoto,8 and their co‐workers have independently reported efficient methods for the synthesis of benzyl and/or aryl indium reagents (mainly activated by using LiCl as reaction additive). However, until now there has been no straightforward method to prepare the synthetically more useful alkyl indium reagent by using readily available alkyl halides, probably because of the low reactivity of indium and alkyl halide, which makes the direct preparation of alkyl indium reagent from alkyl halide extremely difficult.…”

Preparation of Aryl and Heteroaryl Indium(III) Reagents by the Direct Insertion of Indium in the Presence of LiCl

“…This method was extended to the preparation of heteroaryl indium(III) reagents. Heterocyclic iodides (and a heterocyclic bromide), some of which contained a ketone, aldehyde, or ester functionality, reacted smoothly with indium powder in the presence of LiCl to furnish the heteroaryl indium(III) compounds 1 h-m in 78-97 % yield (Table 1, entries [8][9][10][11][12][13]. This method provides access to organoindium reagents containing a range of important and sensitive functional groups that are not compatible with organozinc reagents.…”

“…Herein, we report a preparation of polyfunctional aryl and heteroaryl indium(III) reagents 1 through the direct insertion of indium metal in the presence of LiCl into iodides 2. To the best of our knowledge, only allyl, propargyl, [5] pentafluorophenyl, [8] and benzyl indium(III) reagents [9] have been prepared by the direct treatment of the corresponding halides with indium metal. Commercially available indium does not react with aryl iodides.…”

Direct Synthesis of Water‐Tolerant Alkyl Indium Reagents and Their Application in Palladium‐Catalyzed Couplings with Aryl Halides

“…[2][3][4][5][6] Among the many organoindium compounds, allylic indium reagent has been extensively studied by Araki, Chan, Li, Lloyd-Jones, our group, and others. [7] In recent years, Knochel, [2,3] Minehan, [4] Chupak, [5] Yamamoto, [8] and their co-workers have independently reported efficient methods for the synthesis of benzyl and/ or aryl indium reagents (mainly activated by using LiCl as reaction additive). However, until now there has been no straightforward method to prepare the synthetically more useful alkyl indium reagent by using readily available alkyl halides, probably because of the low reactivity of indium and alkyl halide, which makes the direct preparation of alkyl indium reagent from alkyl halide extremely difficult.…”