Bis(1‐Methyl‐ortho‐Carboranyl)Borane

Abstract

The Lewis superacid, bis(1‐methyl‐ortho‐carboranyl)borane, is rapidly accessed in two steps. It is a very effective hydroboration reagent capable of B−H addition to alkenes, alkynes, and cyclopropanes. To date, this is the first identified Lewis superacidic secondary borane and most reactive neutral hydroboration reagent.

Recent Advancements in Typical Friedel–Crafts Alkylation Reactions Focused on Targeting Arene Nucleophiles

“…In 2022, Martin and co-workers reported highly efficient FC reactions of 1-F-Ad (Scheme 25 B). 147 Reaction of benzene with 1-F-Ad using 1.0 mol% tris( ortho -carboranyl)borane (B o Cb 3 ) gave 1-Ph-Ad in 90% isolated yield after a short reaction time of 30 minutes.…”

The Effect of Carborane Substituents on the Lewis Acidity of Boranes

“…To analyze the carborane substituent effects on Lewis acidity, three sets of compounds were investigated: H 2 BR, HBR 2 , and BR 3 complexes, where R is either an ortho -, para -, or meta -carborane ( o -C 2 B 10 H 11 , p -C 2 B 10 H 11 , or m -C 2 B 10 H 11 , respectively; see Figure ). The only known compounds for these are the homoleptic tris­( ortho -carboranyl)­borane ( 10 ) and the secondary borane HB­( o -CH 3 –C 2 B 10 H 10 ) 2 , where the ortho -carbon bears C–CH 3 rather than C–H for the latter. − The results are compared to the phenyl- and pentafluorophenyl-substituted variants. The computational methods that were used to assess the Lewis acidity are the hydride, fluoride, and ammonia affinity calculations, the global electrophilicity index (GEI), and LUMO energy levels .…”

“…We recently reported HB­( o -CH 3 –C 2 B 10 H 10 ) 2 , the carborane analogue of Piers’ borane HB­(C 6 F 5 ) 2 , − with C–CH 3 substituents on the ortho -carbon positions of the carborane cages. In this work, the other possible isomers and analogues are considered.…”

Formation of Strong Boron Lewis Acid Sites on Silica

“…HB Me oCb 2 and BrB Me oCb 2 were prepared according to literature procedures. 30 Multinuclear NMR spectra ( 1 H, 13 C{ 1 H}, and 11 B{ 1 H}) were recorded on a Bruker AVANCE III HD 400 or 600 MHz instrument. All solid-state NMR samples were packed in 4 mm zirconia rotors and sealed with a Kel-F cap under an argon or dinitrogen atmosphere in a glovebox.…”

“…28 Lewis acidity was not studied in these examples, but B(OR) 3 species, even when containing perfluorinated alkoxy groups, are mild Lewis acids. 29 This paper describes the reaction of bis(1-methyl-orthocarboranyl)borane (HB Me oCb 2 ) 30 with SiO 2-700 , Figure 2c. HB Me oCb 2 is a Lewis superacid, defined as Lewis acids having higher fluoride ion affinity (FIA) than that of SbF 5 .…”