Heteroelement Analogues of Benzoxaborole and Related Ring Expanded Systems.

The review covers the chemistry of organoboron heterocycles structurally related to benzoxaboroles where one of the carbon atoms in a boracycle or a fused benzene ring is replaced by a heteroelement such as boron, silicon, tin, nitrogen, phosphorus, or iodine. Related ring expanded systems including those based on naphthalene and biphenyl cores are also described. The information on synthetic methodology as well as the basic structural and physicochemical characteristics of these emerging heterocycles is complemented by a presentation of their potential applications in organic synthesis and medicinal chemistry, the latter aspect being mostly focused on the promising antimicrobial activity of selected compounds.

Boronate Covalent and Hybrid Organic Frameworks Featuring PIII and P=O Lewis Base Sites.

Invited for the cover of this issue is Sergiusz Lulinski and his co-workers from Warsaw University of Technology and University of Warsaw. The image depicts a journey through the interior of the porous Covalent Organic Framework containing phosphorus and boron centres with carbon dioxygen trapped inside an imagined cave. Read the full text of the article at 10.1002/chem.202001960.

Boronate Covalent and Hybrid Organic Frameworks Featuring PIII and P=O Lewis Base Sites.

Two covalent organic frameworks comprising Lewis basic PIII centers and Lewis acidic boron atoms were prepared by poly-condensation reactions of newly obtained tris(4-diisopropoxyborylphenyl)phosphine with 2,3,6,7,10,11-hexahydroxytriphenylene and 2,3,6,7-tetrahydroxy-9,10-dimethylanthracene. Obtained materials exhibit significant sorption of dihydrogen (100 cm3 g-1 at 1 bar at 77 K), methane (20 cm3 g-1 at 1 bar at 273 K) and carbon dioxide (50 cm3 g-1 at 1 bar at 273 K). They were exploited as solid-state ligands for coordination of Pd0 centers. Alternatively, in a bottom-up approach, boronated phosphine was treated with Pd2 dba3 and poly-condensated, yielding hybrid materials where the polymer networks are formed by means of covalent boronate linkages and coordination P-Pd bonds. In addition, the analogous materials based on phosphine oxide were synthesized. The DFT calculations on framework-guest interactions revealed that the behavior of adjacent boron and phosphorus/phosphine oxide centers is reminiscent of that found in Frustrated Lewis Pairs and may improve sorption of selected molecules.