Regio‐ and Stereoselective Generation of Alkenylindium Compounds from Indium Tribromide, Alkynes, and Ketene Silyl Acetals

Abstract

InBr3 unterstützt die Addition von Ketensilylacetalen an monosubstituierte Alkine zu 2,2‐disubstituierten Alkenylindiumverbindungen mit hoher Regio‐ und Stereoselektivität (siehe Schema). Die Alkenylindiumderivate wurden anschließend in Gegenwart eines Palladiumkatalysators mit Iodbenzol gekuppelt.

A Heteroarylamine Library: Indium‐Catalyzed Nucleophilic Aromatic Substitution of Alkoxyheteroarenes with Amines

“…First up is the coordination of 2 a to the indium Lewis acid ( In ) to form In −thienyl π‐complex 12 ,, wherein In withdraws the electron from 2 a , which then becomes highly electrophilic to accept amine nucleophile 1 ‐ d . The attack of 1 ‐ d to 12 occurs from the side opposite to the coordinated In to afford allylindium type intermediate 13 ‐ d or 13′ ‐ d , which subsequently undergoes regioselective deuteration at the γ site of the allylindium unit by the migration of the D + from the R 1 R 2 N + D moiety, as previously demonstrated . The elimination of MeOH(D) from 14 ‐5‐ d or 14′ ‐3‐ d for the re‐aromatization provides desired product 3 ‐5‐ d or 3 ‐3‐ d , respectively.…”

Indium Tribromide Catalyzed Coupling Reaction of Enol Ethers with Silyl Ketene Imines toward the Synthesis of β,γ‐Unsaturated Nitriles

“…GaBr 3 and InBr 3 afforded the corresponding b,g-unsaturated nitrile 3aa in only 21 and 29 %y ield, respectively,a lthough these catalysts are effective in coupling reactions using ketene silyl acetals [8] ( Table 1, entries 1a nd 2). Interestingly,t he addition of 20 mol %M e 3 SiBr accelerated the catalytic reaction, andp articularly the combination of InBr 3 with Me 3 SiBr afforded an excellent yield of compound 3aa ( 3 showed no catalytic ability ( Table 1, entries [14][15][16][17].…”

“…Then, ar egioselective carboindation by the nucleophilic attack of compound 2 to complex 6 from the opposite side of InBr 3 affords the alkylindium intermediate 7 and TBSBr (Scheme 2B), which is supported by the fact that carboindation reactions of alkynes and alkenes by using ketene silyl acetalsu sually occurs in an anti-addition fashion. [13][14][15] This regioselectivity is due to the stabilization of ap ositive chargeb yt he OR 1 group in the transition state 8.As yn elimination of InBr 2 and the OR 1 groups from the alkylindium 7 occurs to furnisht he b,g-unsa- Scheme2.Plausible mechanism for the initial reaction of vinyl ethers 1 with the SKIs 2.…”

“…We applied this methodology to the formal synthesis of verapamil (14), which is one of the antiarrhythmic agents (Scheme 6). [7b, 19, 20] The alkylation of commercially available3 ,4dimethoxyphenylnitrile (15) (14).…”