Crystalline Neutral Allenic Diborene

A zwitterionic boraalkenyl boronium 3 was synthesized by reduction of cyclic (alkyl)(amino)carbene (cAAC) and trimethylphosphine (PMe₃)‐coordinated tetrabromodiborane 2 with KC₈ in the presence of PMe₃. Further reduction of 3 led to the formation of neutral allenic diborene 4 . X‐ray diffraction and computational studies revealed that 4 features the cumulated C=B and B=B double bonds. The reaction of 4 with four isonitrile molecules afforded a heterocycle 5 with the B₂C₃ five‐membered ring, via a complete scission of the B=B bond of 4 .     

Phosphaborenes: Accessible Reagents for the Synthesis of C−C/P−B Isosteres

Formal exchange of C=C units with isoelectronic B=N or B=P units can provide access to molecules with unique electronic or chemical properties. Herein, we report the simple solution‐phase generation of highly reactive phosphaborenes, RP=BR, and demonstrate their use for the introduction of P=B units into organic systems. Ring opening of a P−B‐containing cyclobutene isostere provided access to unique 1,4‐boraphosphabutadiene systems with conjugated main‐group multiple bonds.     

Nucleophilic addition of TMSCCl3 to N-phosphinoyl benzaldimines: a route to N-phosphinoyl-α-(trichloromethyl)benzylamines

Nucleophilic addition of readily available TMSCCl₃ to N-phosphinoyl benzaldimines allows preparation of N-phosphinoyl-α-(trichloromethyl)benzylamines. Typically, the reaction in THF at room temperature using tetrabutylammonium difluorotriphenylsilicate (TBAT) as a catalytic promoter, afforded very good yields (65–95% range) for most derivatives within 1 h at room temperature.