Lewis and Brønsted multifunctionality: an unusual heterocycle from the reaction of bis(pentafluorophenyl)borinic acid with nitriles

Abstract

The combination of Lewis and Brønsted acidity as well as Lewis basicity in (C6F5)2BOH results in a remarkable reactivity towards organonitriles to give novel heterocyclic compounds containing a BOBOCN six-membered ring.

Borane Adducts of Hydrazoic Acid and Organic Azides: Intermediates for the Formation of Aminoboranes

“…Compound 4 is probably formed by the addition of free HO−B(C 6 F 5 ) 2 to the triple bond of an acetonitrile adduct of the type HOB(C 6 F 5 ) 2 ⋅N≡C−CH 3 followed by ring closure. The solvate‐free species has already been reported …”

“…[38] The transfer of aC 6 F 5 group from boron to another main group element was also observed in the decomposition of the adduct formed between abis(amino)silylene and B(C 6 F 5 ) 3 within one month. [41] To gain further insight into the stability of azide-borane adducts,B (C 6 F 3 ) 3 was reacted with as eries of different covalently bound azides RN 3 (R = TMS (Me 3 Si), Ph, and Btp (3,5-(CF 3 ) 2 C 6 H 3 ;T able 1). [40] As expected, hydrolysis of 2H with aw ater/acetonitrile mixture led to the formation of the free amine H 2 N(C 6 F 5 ) (3H; Figure S21, Scheme 2), in addition to HC 6 F 5 and B(OH) 3 in good yields (yield of isolated substance = 72 %, m.p.358 8C).…”

“…Interestingly,w hen the hydrolysis was stopped shortly after water addition by adding MgSO 4 to the mixture,t he formation of ap uckered six-membered-ring species (4·CH 3 CN) was observed (Figure 3), indirectly confirming the intermediate formation of HOB(C 6 F 5 ) 2 in the first hydrolysis step.C ompound 4 is probably formed by the addition of free HOÀB(C 6 F 5 ) 2 to the triple bond of an acetonitrile adduct of the type HOB(C 6 F 5 ) 2 ·NCÀCH 3 followed by ring closure.T he solvate-free species has already been reported. [41] To gain further insight into the stability of azide-borane adducts,B (C 6 F 3 ) 3 was reacted with as eries of different covalently bound azides RN 3 (R = TMS (Me 3 Si), Ph, and Btp (3,5-(CF 3 ) 2 C 6 H 3 ;T able 1). It was only possible to isolate the adducts 1R for PhN 3 and TMSN 3 (Figure 4), while in the case of BtpN 3 ,i mmediate decomposition into 2Btp and N 2 was observed ( Table 1).…”

Boran‐Addukte von Stickstoffwasserstoffsäure und Organischen Aziden: Intermediate bei der Bildung von Aminoboranen

“…B. wenn B(C 6 F 5 ) 3 als Katalysator verwendet wird. [41] Um weitere Erkenntnisse zur Stabilitätv on Azid-Boran-Addukten zu gewinnen, wurde die Reaktion von B(C 6 F 3 ) 3 mit einer Reihe von verschiedenen kovalent gebundenen Aziden R-N 3 (R = TMS,P h, Btp) untersucht (Tabelle 1). Interessanterweise konnte die Bildung eines gewellten Ringsystems (4·CH 3 CN,A bbildung 3) beobachtet werden, wenn die Hydrolyse kurz nach Zugabe des Wassers mittels MgSO 4 gestoppt wurde.D ies zeigt indirekt, dass im ersten Hydrolyseschritt intermediär HOB(C 6 F 5 ) 2 gebildet wird.…”

“…Verbindung 4 wird wahrscheinlich durch Addition von HOÀB(C 6 F 5 ) 2 an die Dreifachbindung eines Acetonitril-Addukts vom Ty pH OB(C 6 F 5 ) 2 ·NCÀCH 3 gebildet, gefolgt von einem Ringschluss.D ie entsprechende solvatfreie Spezies wurde bereits publiziert. [41] Um weitere Erkenntnisse zur Stabilitätv on Azid-Boran-Addukten zu gewinnen, wurde die Reaktion von B(C 6 F 3 ) 3 mit einer Reihe von verschiedenen kovalent gebundenen Aziden R-N 3 (R = TMS,P h, Btp) untersucht (Tabelle 1). Nur bei PhÀN 3 und TMSÀN 3 war es mçglich, die Addukte 1R zu isolieren (Abbildung 4), wohingegen bei Btp À N 3 eine sofortige Zersetzung zu 2Btp und N 2 beobachtet wurde (Tabelle 1).…”