Rh^III‐Catalyzed Functionalization of closo‐Dodecaborates by Selective B−H Activation: Bypassing Competitive C−H Activation

Abstract

The closo-dodecaborate dianion is a fundamental icosahedral boron cage with 12 identical B-H vertices. The chemistry and applications of boron clusters have inspired researchers ever since their discovery several decades ago, and the selective modification of the cage positions has remained a major synthetic challenge. A rhodium(III)-catalyzed B-H functionalization-cyclization cascade of closo-dodecaborate amides is reported. The transformations occur chemoselectively at B-H positions in the presence of C-H bonds prone to competitive cyclometalation. Previously inaccessible cage derivatives with B-C(sp ) and B-C(sp ) bonds as well as a fused diboraoxazole ring are obtained in a one-pot process. The reactions proceed under mild conditions and exhibit complete cage regioselectivity with broad functional group tolerance. These cluster derivatives enable a largely extended investigation of the application of anionic boron clusters in research areas such as photoluminescent materials and medicinal chemistry.

Structural properties of bioactive peptides with α‐glucosidase inhibitory activity

“…Among the 43 peptides evaluated for α-glucosidase inhibition, only nine were resistant to GIT digestion by a combination of pepsin, trypsin and chymotrypsin as predicted by BIOPEP (http://www.uwm.edu.pl/biochemia/ index.php/en/biopep) database (Table 2). [35] Therefore, it is possible for some of these αglucosidase inhibitory peptides to still serve a dual function of low to moderate inhibition of α-glucosidase and DPP-IV. The highly potent peptides predicted to be stable to GIT digestion were SQSPA [28] and TPSPR [20] with IC 50 values of 20 and 40.02 μm, respectively.…”

Natural-Product-Directed Catalytic Stereoselective Synthesis of Functionalized Fused Borane Cluster–Oxazoles for the Discovery of Bactericidal Agents

“…This peak pattern was in full agreement with that observed for related dodecaborates in earlier studies. 61 , 64 …”

“… 59 − 64 For dodecaborates, ureido and amide functionalities can serve as directing groups to achieve B–C and concomitant B–O bond formation. 61 , 64 …”

Synthesis of Polyhedral Borane Cluster Fused Heterocycles via Transition Metal Catalyzed B-H Activation

“…Mechanism studies indicate the alkenylation occurs prior to annulation in this one pot transformation, and a plausible mechanism involving Rh I /Rh III catalyzed dual B-H activation was proposed based on the isolation of a rhodium agostic intermediate. Later, the same group further extended the cascade alkenylation/annulation of dodecaborates with amide as directing group [54]. This transformation displays broad functional group tolerance and complete cage regioselectivity, and a series of dodecaborate-fused oxazoles were synthesized with moderate to good yields ( Figure 6).…”