�Click� chemistry as coined by Sharpless in 20011 refers a set of reactions which allow the easy formation of molecules in a quick and reliable way. The model and most prominent example for �click� chemistry is the 1,3-dipolar cycloaddition of alkynes and azides to yield 1,2,3-triazoles. The thermal variant was first described by Huisgen.2 Although a number of boron substituted azides (R2BN3)3-5 and alkynes (RC=CBR2, R = alkyl or aryl)6-9 have been reported, only a few examples of their application in click chemistry are known. Harrity et al. described the cycloaddition of an alkynylborante with benzyl azide leading to a boron substituted 1,2,3-triazole.10 The first cycloaddition reaction of a boron azide with C=C bonds was described by Curran et al. to give NHC-boryl triazoles.11 Recently, we extended this scope to the 1,3-dipolar cycloaddition reaction of the boron azide, Cy2BN3, with electron-poor acetylenes.12We will report the unusual and uncatalyzed reaction of bispentafluorophenylboron substituted alkynes and azides leading to an exceptional five-membered BCN3 heterocycle via the C�H activation of the aromatic solvent benzene and toluene, respectively. While subsequent treatment with PMe3, gave the P�B adduct with the exocyclic boron, reaction with PtBu3effected deprotonation of the heterocycle to give the corresponding phosphonium salts. Moreover, mechanistic considerations for the formation of this remarkable reaction product will be presented.References1 H. C. Kolb, M. G. Finn, K. B. Sharpless, Angew. Chem. Int. Ed. 2001  , 40, 2004-2021; Angew. Chem. 2001  , 113, 2056-2075.2 R. Huisgen, Angew. Chem. Int. Ed. 1963  , 2, 565-598; Angew. Chem. 1963  , 75, 604-637.3 P. J. Paetzold, H.-J. Hansen, Z. Anorg. Allg. Chem. 1966  , 345, 79-86.4 P. I. Paetzold, P. P. Habereder, R. M�llbauer, J. Organomet. Chem. 1967  , 7, 45-50.5 P. I. Paetzold, G. Maier, Angew. Chem. Int. Ed. 1964  , 3, 315-315; Angew. Chem. 1964  , 76, 343-344.6 B. Wrackmeyer, H. N�th, Chem. Ber. 1977  , 110, 1086-1094.7 R. K�ster, H.-J. Horstsch�fer, P. Binger, Justus Liebigs Annalen der Chemie 1968  , 717, 1-23.8 W. Siebert, R. Full, T. Renk, A. Ospici, Z. Anorg. Allg. Chem. 1975  , 418, 273-278.9 H. C. Brown, J. A. Sinclair, J. Organomet. Chem. 1977  , 131, 163-169.10 J. Huang, S. J. F. Macdonald, J. P. A. Harrity, Chem. Commun. 2009  , 0, 436-438.11 E. Merling, V. Lamm, S. J. Geib, E. Lac�te, D. P. Curran, Org. Lett. 2012  , 14, 2690-2693.12 R. L. Melen, D. W. Stephan, Dalton Trans. 2013  , 42, 4795-4798.

Boron perturbed click reactions prompt aromatic C�H activations

248th National Meeting (2014)

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