An Approach Towards Functional Dendrimers Based on the Hydroboration Reaction and Spontaneous Boron–Nitrogen Bond Formation

Abstract

Abstract The reaction of 1,4‐bis‐ or 1,3,5‐tris(bromoboryl)benzenes 4 and 6 , respectively, with 2 or 3 equiv. of 4,4′‐bis(but‐3′′‐enyl)‐2,2′‐bipyridyl ( 2 ) leads to the corresponding 2,2′‐bipyridylboronium cations 5 and 7 in almost quantitative yield. Using the monocation [(MeC 6 H 4 )B(Br){4,4′‐bis(but‐3′′‐enyl)‐2,2′‐bipyridyl}] + ( 3Br ) as a model system, it is shown that the olefinic side‐chains of such compounds are readily transformed into alkyldibromoborane functionalities by hydroboration with HBBr 2 . Subsequent addition of 4,4′‐dimethyl‐2,2′‐bipyridyl leads to the formation of a branched system of three 2,2′‐bipyridylboronium cations ( 9Br ). The species 5 and 7 can be regarded as generation zero (G 0 ) 2,2′‐bipyridylboronium dendrimers, and the hydroboration/B–N adduct formation sequence offers a convenient route for the assembly of higher generations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)