Synthesis, Structure, and Reactivity of Borate Ester Coordinated Organobismuth Compounds

Abstract

A new class of hypervalent organobismuth compounds functionalized with coordinating pinacolborate esters of the nature ArBiCl 2 (2), Ar 3 Bi (3), ArPh 2 Bi (4), Ar 3 BiCl 2 (5), and ArPh 2 BiCl 2 (6), where Ar ) 3-fluoro-2-pinacolatoboronphenyl, have been prepared and structurally characterized. The Bi • • • O distance is between 2.58 and 3.47 Å in the solid state for all compounds, and reasonable bonding interactions are presumed to exist in compounds 2-4 and 6, where Bi • • • O < 3.0 Å. When ArPh 2 BiCl 2 ( 6) is exposed to CsF in the presence of furan, the [4 + 2] cycloaddition product of 3-fluorobenzyne + furan, 8, is isolated in 58% yield. Mechanistic evidence is offered to support the claim that 6 undergoes an unprecedented fluoride-promoted fragmentation to generate 3-fluorobenzyne, pinacol, BF 3 , and Ph 2 BiF.

Organobismuth Reagents: Synthesis, Properties and Applications in Organic Synthesis

“…compounds IX and X). 95 Similar interactions within ortho-substituted triarylbismuthines were also observed by Caires 61 in 2008 and by Silvestru in 2010. 159 Hypervalent interactions have also been identified in pentavalent organobismuth compounds (Scheme 6 B).…”

“…The introduction of more reactive functional groups on triarylbismuthines was accomplished using Grignard reagents prepared using Knochel's conditions (Step 14a). 60 Triarylbismuthines bearing imines, 56 nitriles, 51,56 esters 51,56 or borate esters 61 have been prepared using this approach.…”

“…64,67 More elaborate functional groups such as borate esters were later introduced on mixed triarylbismuthines using Grignard reagents prepared via magnesium-halogen exchange according to Knochel's procedure. 61 The addition of organolithium reagents on diarylbismuth halide also constitutes an efficient approach to the synthesis of mixed arylbismuth reagents (Step 27b). 65,68 The organolithium reagents can be prepared by lithium-halogen exchange or by direct lithiation of the aromatic precursor.…”

Synthesis, Properties Characterization and Applications of Various Organobismuth Compounds

“…Caires et al [ 55 ] reported the first example of organobismuth compounds which contained organic boron groups. These organobismuth complexes were synthesized with a borate ester moiety because of its relative rarity as an oxygen donor in coordination compounds.…”

Electrophilic ipso-iodination of silylated arylboronic acids

“…Iodinated arylboronic acids are attractive synthetic intermediates as they possess two sites, which can be employed in coupling reactions. Thus, pinacol esters of simple iodophenylboronic acids were used as precursors of magnesiumeboron bimetallics followed by the treatment with electrophiles to give functionalized arylboronic esters [1,2]. Recently, 2-iodophenylboronic acid was found to be an effective catalyst for the direct formation of amides from carboxylic acids and amines [3].…”