Investigations on the reactivity of arylboronic acid with phenolic pyrazole

Reaction of phenylboronic acid with phenolic pyrazole was carried out in 1:1 stochiometry using toluene as a solvent. Depending on the steric bulk of the group present on the pyrazole ring, PhB (HPhPzPh)(OEt) 1, [(PhB)(PhPzHt-Bu)(OH)][(PhB)2(PhPzt-Bu)2(O)] 2 and (PhBPhPz)23 were isolated. Compound 3 is an example of cis-isomer of pyrazabole crystallized in a boat conformation for the B2N4 heterocycle.

Graphical abstractInvestigations of the reactivity of phenolic pyrazoles (O,N,N-type ligand) with arylboronic acids has yielded an organoboron monometallic compound, an oxo bridged dimer and B2N4 heterocycle pyrazabole in good yields. By varying the group on the 5-position of the pyrazole ring the ligand binding modes vary from being a O,N-chelating to both chelating and bridging modes leading to the formation of the interesting cis-pyrazabole heterocycle.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Organoboron compounds have numerous applications in the fields ranging from organic synthesis to materials chemistry. ► Reaction of phenylboronic acid with phenolic pyrazole affords interesting organoboron compounds. ► Isolation of such diverse products has been possible by modifying the steric groups on the ligand.