The catechol‐substituted monoborylacetylenes 1a−d are obtained from the reaction of bis(diisopropylamino)borylacetylene with catechol derivatives and 2,2′‐biphenol. The catalytic trimerization of 1a−d with [(η5‐C5H5)Co(CO)2] yields isomeric mixtures of the triborylbenzene derivatives 2a,2a′, 2b,2b′, and 2c,2c′. The reaction of 2a,2a′ with mesityllithium provides the hexamesityl‐substituted 1,3,5‐triborylbenzene 2e. Hydroboration of 1a with catecholborane affords a mixture of 1,1‐bis(1,3,2‐benzodioxaborol‐2‐yl)ethene (3a) and trans‐1,2‐bis(1,3,2‐benzodioxaborol‐2‐yl)ethene (4a). Hydroboration of 1a and 3a with one or two mol of HBCl2 and subsequent substitution of the chlorine atoms of the product with catechol leads in each case to the 1,1,1‐trisborylmethane derivative 5a in 83 and 78% yield, respectively, which forms the tris(THF) adduct 5a(thf)3. Treatment of 5a with tBuLi yields 1,1,1‐tris[di(tert‐butyl)boryl]ethane 6a. [Co2(CO)8] reacts with 1a to give 3‐(1,3,2‐benzodioxaborol‐2‐yl)‐1,2‐bis(tricarbonylcobalta)tetrahedrane (9a). The new compounds have been characterized by NMR spectroscopy and mass spectrometry as well as by X‐ray structure analyses for 1a, 3a, 5a, 5a(thf)3, and 9a.
