A metal-free 1,4-allylation of azadienes with allyltrimethylsilanes catalyzed by B(C6F5)3 has been developed for the first time to afford benzofuran-, indene-, dihydronaphthalene-, chromene-, and benzothiophene-ba...
Cationic Symmetrically and Unsymmetrically Substituted Diboranes and Bis(diboranes) with Direct Boron‐Boron Bond: Synthesis by Substitution, Stability and Properties
Von Wiley-VCH zur Verfügung gestellt
New strategies for the directed synthesis of unsymmetrically-substituted diboranes are established; the kinetics of substitution of the triflato group in monocationic triflato-diboranes is controlled by the properties of the neutral Lewis base bound to the second boron atom.
Starting with diboranes with two electron-rich bridging bicyclic guanidinate substituents, we report in this work the rational synthesis of new dicationic symmetrically- and unsymmetrically-substituted diboranes in SN1-type substitution reactions in which triflato or bromo substituents are replaced by neutral Lewis bases. The scope of such substitution reactions and their rate are analyzed with different pyridine derivatives of variable Lewis basicity. The first substitution step, leading to a monocationic diborane with one anionic substituent (triflate or bromide) and one neutral Lewis base, proceeds much faster than the second substitution step leading to a dicationic diborane with two neutral Lewis bases. The different time scales for the substitution steps could be used to conveniently synthesize in one-pot reactions several dicationic, unsymmetrically-substituted diboranes with two different neutral Lewis bases.Zum Volltext
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