Boronate electron-withdrawing behavior

The preparative availability of the theoretically investigated disubstituted para-dodecaborates, which are shown in Figures 13.7 and 13.8 will pose problems, because electrophilic substitutions take place not only in the desired para-position (1,12-isomer) rather, the 1,7-isomer will be the main prodnct, as predicted by calculations of Hoffmann and Lipscomb (1962) an inductively electron-withdrawing substituent will direct the second substitntion to boron 7 and 12 in a ratio 5 1. In the case of an electron-donating substituent, the electrophilic snbstitution occurs in mefa-position 2. Examples for this behavior are the halogenation (Knoth et al., 1964) and amination (Hertler and Raasch, 1964) of the Bi2-species. 

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