Tomasz Kliś

Pyrazole complexes of acyloxydialkylboranes

Abstract The reaction of Me3CCOOBEt2 with pyrazole led to the formation of the stable addition complex 1, which was found to be monomeric in solution. The reaction of 9-H-9-borabicyclo[3.3.1]nonane (9-H-9-BBN)2 with pyrazole and pivalic acid yielded a similar complex Me3CCOO(9-BBN)-pzH 2. Crystallographic analysis of 2 revealed a dimeric structure due to the strong hydrogen bonding between azole hydrogen and carbonyl oxygen. The one boron–carbon bond of compound 1 cleaves readily with triethylborane at 20°C with the evolution of ethane, giving a species Me3CCOO(BEt2)2pz 3 with a seven-membered heterocyclic ring as the main structural feature.

Crystal structure of (2′,3,6′-tri­chloro­biphenyl-2-yl)boronic acid tetra­hydro­furan monosolvate

In this manuscript the molecular and supramolecular structure of 2′,3,6′-trichlorobiphenyl-2-ylboronic acid tetrahydrofuran monosolvate is presented

Crystal structure of (2-benzyl­oxy­pyrimidin-5-yl)boronic acid

The boronic acid group in the title compound, C11H11BN2O3, adopts a syn–anti conformation and is almost coplanar with the aromatic rings , making a dihedralangle of 3.8 (2)°. In the crystal, adjacent molecules are linked via pairs of O—H⋯O interactions, forming centrosymmetric dimers with an R 2 2(8) motif, which have recently been shown to be energetically very favorable (Durka et al., 2012 ▶, 2014 ▶). The hydroxy groups in an anti conformation are engaged in lateral hydrogen-bonding interactions with N atoms from neighbouring molecules, leading to the formation of chains along [001]. O⋯B [3.136 (2) Å] and C(π)⋯B [3.393 (2) Å] stacking interactions in turn link parallel chains of centrosymmetric dimers into layers parallel to (010).