Frustrated Lewis pair behavior of monomeric (boryl)iminomethanes accessed from isocyanide 1,1-hydroboration

Abstract

The activation of carbon dioxide, organonitriles, and terminal acetylenes by (boryl)iminomethanes derived from isocyanide 1,1-hydroboration is described. Also detailed is the generality of hydroboration of m-terphenylisocyanides with hydroboranes of differing Lewis acidities.

Oxidative‐Insertion Reactivity Across a Geometrically Constrained Metal→Borane Interaction

“…Accordingly,addition of 1-adamantyl azide (AdN 3 )orp-tolyl azide (p-TolN 3 )t on-pentane solutions of 1 results in 1,1insertion of the terminal N(Ng)into the Pt!Bbond to give the new metalacycles 2 (82 %y ield) and 3 (57 %y ield), respectively,a sd etermined by X-ray diffraction (Scheme 1 and Figure 1). This migration process,w hich preserves atricoordinate boron center,has been observed previously in (boryl)iminomethane chemistry, [33,37] and results in the transformation of the Cy2 BIM ligand into af ormally dianionic (boryl)diazenylamido chelate.T he formal Pt II centers in complexes 2 and 3 also engage in asignificant h 1 -C interaction with the ipso carbon atom of one m-terphenyl flanking Dipp ring ( Figure 1). This migration process,w hich preserves atricoordinate boron center,has been observed previously in (boryl)iminomethane chemistry, [33,37] and results in the transformation of the Cy2 BIM ligand into af ormally dianionic (boryl)diazenylamido chelate.T he formal Pt II centers in complexes 2 and 3 also engage in asignificant h 1 -C interaction with the ipso carbon atom of one m-terphenyl flanking Dipp ring ( Figure 1).…”

“…While 6 and 7 were not isolated from these mixtures,t hey are selectively formed upon addition of as toichiometric amount of either CO 2 [37] or tBuNCO to unligated Cy2 BIM (see the Supporting Information). Notably,this reaction proceeds for 18 hours at room temperature without the buildup of detectable intermediates as determined by 1 HNMR spectroscopy.Contrastingly,treatment of 1 with tert-butylisocyanate does not lead to ap roductive reaction at room temperature.H owever,w hen the reaction is heated to 50 8 8C, a2 :1 mixture of the boraurea 7 and [Pt(CNAr Dipp2 ) 2 ]a re generated as the only observed products (Scheme 1).…”

Katalytische Synthese von Kaliumacyltrifluoroboraten mithilfe chemoselektiver Kreuzkupplung eines bifunktionalen Reagenzes

“…[13, 16b,c] Kupfer soll auch die Reaktion durch Bindung des freien PPh 3 beschleunigen. Iminium 9 ist von Formylacyltrifluoroborat [17] abgeleitet, das jedoch noch nicht isoliert wurde.U nsere bisherigen Bemühungen, 9 zu Formyl-KAT umzuformen, blieben erfolglos,j edoch wäre dies interessant fürweitere Untersuchungen. Durch Versetzen mit Kupfer kann die Reaktion bei milderen Temperaturen ausgeführt werden.…”

“…Kreuzkupplungen bei hçheren Te mperaturen (100 8 8Cund hçher) sind auch ohne Kupfersalze in geringen Ausbeuten mçglich. Iminium 9 ist von Formylacyltrifluoroborat[17] abgeleitet, das jedoch noch nicht isoliert wurde.U nsere bisherigen Bemühungen, 9 zu Formyl-KAT umzuformen, blieben erfolglos,j edoch wäre dies interessant fürweitere Untersuchungen.Diese Methode verbessert nicht nur die Mçglichkeiten zur Synthese von KATs,s ondern zeigt auch, wie KATs als einzigartige Vorstufen für a-Aminoborverbindungen nützlich sind. [1c,d] Diese Substrate sind vor allem interessant fürd as Design und die Entwicklung von Wirkstoffen [18].…”

Catalytic Synthesis of Potassium Acyltrifluoroborates (KATs) through Chemoselective Cross‐Coupling with a Bifunctional Reagent

“…Hydrolysist othe KAT led to amixture containing the 1,4-aza HNMe 2 addition product. [16d] This effect is particularly significant for aryl iodides,s ince the iodo ligand raises the barrier for the transmetallation and consequently the addition of copper reduces the need for elevated reaction temperatures.I ti sp ossible to perform the cross-coupling at higher temperatures (100 8 8Cand above) without the presence of copper salts,b ut with diminished yields.I nterestingly, iminium 9 would be derived from af ormyl acyltrifluoroborate, [17] which has not previously been isolated. [e] Reported yields are of isolated product.…”