1,2-Dehydro-o-carborane (o-carboryne) (2  ), a very reactive intermediate reported first in 1990,1 is regarded as a three-dimensional relative of benzyne (1  ) and known to undergo [4+2] cycloaddition reaction with polycyclic and hetero aromatics.1,2 1,3-Dehydro-o-carborane (1,3-o-carboryne) (3  ), which might feature a cage C-B multiple bond, however, remained less developed. The only reported preparation of 3  is from 3-iodo-1-lithio-o-carborane mediated by palladium(0).3 3-diazonium-o-carborane tetrafluoroborate (4  ) were prepared as a transition-metal-free precursor for the generation of 3  . Such reactive intermediate could be trapped by various alkylbenzenes to afford [4+2] and ene products in moderate to good yields by treatment of 4  with one equiv of lithium diisopropylamide (LDA) as shown in the scheme.(1) Gingrich, H. L.; Ghosh, T.; Huang, Q.; Jones, M. Jr. J. Am. Chem. Soc. 1990  , 112, 4082-4083.(2) Ghosh, T.; Gingrich, H. L.; Kam, C. K.; Mobraaten, E. C.; Jones, M. Jr. J. Am. Chem. Soc. 1990  , 113, 1313-1318.(3) Qiu, Z.; Xie, Z. J. Am. Chem. Soc. 2010  , 132, 16085-16093

Synthesis and reactivity study of an efficient precursor for transition-metal-free 1,3-dehydro-o-carborane

247th National Meeting (2014)

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