We
report herein versatile, transition metal-free and additive-free
(hetero)aryl–aryl coupling reactions promoted by the oxidative
electrocoupling of unsymmetrical tetra(hetero)arylborates (TABs) prepared
from ligand-exchange reactions on potassium trifluoroarylborates.
Exploiting the power of electrochemical oxidations, this method complements
the existing organoboron toolbox. We demonstrate the broad scope,
scalability, and robustness of this unconventional catalyst-free transformation,
leading to functionalized biaryls and ultimately furnishing drug-like
small molecules, as well as late stage derivatization of natural compounds.
In addition, the observed selectivity of the oxidative coupling reaction
is related to the electronic structure of the TABs through quantum-chemical
calculations and experimental investigations.
A novel, one-step
N-dehydrogenation of amides to enamides is reported.
This reaction employs the unlikely combination of LiHMDS and triflic
anhydride, which serves as both the electrophilic activator and the
oxidant, and is characterized by its simple setup and broad substrate
scope. The synthetic utility of the formed enamides was readily demonstrated
in a range of downstream transformations.
A catalytic 1,1‐difunctionalization of unactivated olefins en route to sp3 bis‐organometallic B,B(Si)‐reagents is described. The protocol is characterized by exceptional reaction rates, mild conditions, wide scope, and exquisite selectivity pattern, constituting a new platform to access sp3 bis‐organometallics.
Since the nowadays used lead-based primary explosives, lead azide, picrate and styphnate suffer from various environmental and toxic issues, there is a great need for new green materials. Therefore, two highly promising lead-free primary explosives potassium 1-(N-nitramino)-5Htetrazolate (1, 1-KNAT) and potassium 2-(N-nitramino)-5Htetrazolate (2, 2-KNAT) have been synthesized and characterized. Both isomers show superior energetic performance, initiation capability and were comprehensively analyzed by low-temperature X-ray diffraction, IR, multinuclear NMR spectroscopy, elemental analysis, and DTA. Sensitivity determinations toward impact, friction, and electrostatic discharge revealed its highly powerful, but also sensitive character. In addition, their potential as lead-free primaries were evaluated in initiation tests of PETN or RDX filled detonators confirming their great suitability as lead-free primary explosives. Figure 7. A) and B) HN test of 1 and 2; C) and D) HP test of 1 and 2; E) Positive PETN (left) and RDX (right) initiation tests with 5 mg of compound 1 (bottom) and 2 (top).
An alternative and
complementary transformation for the synthesis
of aryl- and heteroaryl-substituted alkynes is presented that relies
on a chemoselective electrocoupling process. Tetraorganoborate substrates
were logically designed and simply accessed by transmetalations using
readily or commercially available organotrifluoroborate salts.
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