Palladium catalysed synthesis of cyclic amidines and imidates

Ketenimines from Isocyanides and Allyl Carbonates: Palladium‐Catalyzed Synthesis of β,γ‐Unsaturated Amides and Tetrazoles

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The reaction of allyl ethyl carbonates with isocyanides in the presence of ac atalytic amount of Pd(OAc) 2 provided ketenimines through b-hydride elimination of the allyl imidoylpalladium intermediates.T he insertion of the isocyanide into the p-allyl Pd complex proceeded via an unusual h 1 -allyl Pd species.T he resulting ketenimines were hydrolyzed to b,g-unsaturated carboxamides during purification by flash column chromatography on silica gel or converted in situ into 1,5-disubstituted tetrazoles by [3+ +2] cycloaddition with hydrazoic acid or trimethylsilyl azide.There has been increased interest in the exploitation of isocyanides as ao ne-carbon-atom synthons in transitionmetal-catalyzed insertion reactions in the last decade. [1] Isoelectronic with carbon monoxide,i socyanides possess additional advantages of being tunable both electronically and sterically,a nd are easy to handle.F ollowing the seminal contribution by Whitby and co-workers on the palladiumcatalyzed three-component reaction of isocyanides,a ryl halides,a nd amines, [2] at in-free version of the synthesis of amidines as described by Kosugi, Migita, and co-workers, [3] many elegant transformations have been reported. [4,5] All these reactions involved the generation of aryl or vinyl imidoylpalladium species,f ollowed by ligand exchange and reductive elimination with the formation of ak ey C(sp 2 ) À C(sp 2 )b ond.

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Catalytic Isonitrile Insertions and Condensations Initiated by RNC–X Complexation

“…Intramolecular cyclizations with hydroxyalkyl-substituted aryl bromides afford cyclic imidates. [159] …”

Palladiumkatalysierte migratorische Insertion von Isocyaniden: eine neue Methode für die Kreuzkupplungschemie

“…[14] Überraschenderweise waren in diesem Fall auch andere Isocyanide reaktiv, obgleich mitunter das Produkt der doppelten Insertion (11) in erheblichen Mengen isoliert wurde, wenn sekundäre oder primäre Isocyanide verwendet wurden. [17] In allen Fällen gelang die Bildung des Amidins nur unter Verwendung von tert-Butylisocyanid, während die Bildung der Imidate auch durch Einsatz primärer, sekundärer und tertiärer aliphatischer Isocyanide gelang. [15] Die Autoren zeigten später, dass Alkenylbromide mçgliche Reaktionspartner in diesen Reaktionen sein kçnnen und zu a,b-ungesättigten Amidinen und Imidaten führen.…”