Ein neuer Zugang zu 1,2‐ und 1,3‐Diborol

A New Approach to 1,2‐ and 1,3‐Diborole Herrn Prof. Dr. Joachim Knappe zum 65. Geburtstag gewidmet. Diaminoborylation of 1,3‐dilithiopropenes leads to the (Z)‐1,3‐bis(diaminoboryl)propenes 4a , b , which are transformed by an amine/chlorine exchange to the (Z)‐1,3‐bis(aminochloroboryl)propenes 5a , b. These react with sodium to yield the 2,5‐dihydro‐1 H ‐1,2‐diboroles 2c , d , whereas the reaction with potassium leads to the 2,3‐dihydro‐1 H ‐1,3‐diboroles 6a , b by rearrangement of the C 3 B 2 skeleton. The constitutions of the heterocycles 2c , d and 6a , b are established by X‐ray structure analyses. Reaction of the 1,2‐diboroles 2c , d with (C 5 H 5 )Co(C 2 H 4 ) 2 leads to the red (1‐borabutadiene)cobalt complexes 3c , d. In 3c a sigmatropic rearrangement is studied by NMR spectroscopy.