HYDROBORATION .53. CYCLIC HYDROBORATION OF 1,5-CYCLOOCTADIENE WITH MONOHALOBORANE COMPLEXES - SIMPLE, CONVENIENT SYNTHESIS OF B-HALO-9-BORABICYCLO[3.3.1]NONANES

The hydroboration of 1, 5-cyclooctadiene with stable methyl sulfide complexes of monochloro-, monobromo-, and monoiodoboranes (H2BX-SMe2gives a mixture of B-halo-9-borabicyclo[3.3.1]nonane (B-X-9-BBN) and its [4.2.l] isomer. The thermodynamically less stable [4.2.1] isomer predominates in the mixture. This can be readily converted to the more stable isomer B-X-9-BBN by gentle heating. The methyl sulfide complexes are isolated as stable crystalline solids. Distillation, following the addition of 1 equiv of the respective boron trihalide, provides B-X-9-BBN free from SMe2. These compounds have been characterized by physical and chemical means. They exhibit promise as synthetic intermediates. © 1979, American Chemical Society. All rights reserved.