Triethylsilane−Indium(III) Chloride System as a Radical Reagent

Abstract

[reaction: see text] A novel generation method of indium hydride (Cl2InH) was found by the transmetalation of InCl3 with Et3SiH. In the intramolecular cyclization of enynes, the previously reported system (NaBH4-InCl3) has a problem of side reactions with the coexistent borane. In contrast, the problem was solved by the presented system, which affords effective hydroindation of alkynes.

EPR and pulsed ENDOR study of intermediates from reactions of aromatic azides with group 13 metal trichlorides

“…The starting azide (1 mmol) was added at 0 °C to an acetonitrile solution of dichloroindium hydride (1.1 mmol), generated in situ by stirring under an argon atmosphere anhydrous indium trichloride (243 mg, 1.1 mmol, previously dried by heating at 130 °C under argon for 1 h) and triethylsilane (177 μL, 1.1 mmol) in ACN (4 mL) for 5 min at 0 °C [47]. The resulting solution was rapidly transferred into a quartz capillary tube and nitrogen was bubbled inside for few minutes.…”

“…The number of applications of indium [1–6], gallium [7–11] and other group 13 metal derivatives, as promoters of radical reactions, has been increasing ever since the original work of Baba and co-workers with dichloroindium hydride [12–16]. Parallel to that, organic azides are increasingly used as sources of N-centred radicals, although most such methods also require organotin hydrides [17–23].…”

8.26 Reduction of Saturated Alkyl Halides to Alkanes

“…Typically sodium borohydride is often used as the hydride source, 43 other combinations are possible ( Table 2), including Et 3 SiH, which may be less likely to cause side reactions due to adventitious borane formation during the course of the reaction. 44 Hydrosilanes can be used in combination with indium salts to reduce bromo-and iodoalkenes at 70 1C in tetrahydrofuran (THF), or near room temperature in the presence of Et 3 B and air ( Table 2). 45 In situ-generated indium hydride appears comparable to tin hydrides in terms of tolerance to functional groups (as seen in the Scheme 22), 41 and avoids the need for extensive purification to remove tin residues.…”

Radicals in organic synthesis. Part 1

“…75 Cyclisation of enyne 33 proceeds without reduction of the ester moiety to furnish, after acidic hydrolysis of alkenylindium 34, cyclopentane 35 in 53% yield compared to a mere 12% obtained with the indium(III) chloride/sodium borohydride conditions (Scheme 12). The possible reasons for the low yield when sodium borohydride is employed include reduction of the ester moiety and hydroboration mediated by the borane byproduct.…”