1,8-Bis(dimethylamino)naphthalene

A Boronium Ion with Exceptional Electrophilicity

“…[28] Borylation of N-methylindole afforded exclusively the 3-substituted regioisomer, in sharp contrast to the previously reported reaction with B(C 6 F 5 ) 3 , which produces the 2-borylated N-methylindole. [29] Pyrrole 15c gave a mixture of mono-borylated regioisomers along with some of the diborylated 16c using one equivalent of 8a (ca.…”

“…In principle, these requirements might be satisfied by 1,8-bis(dimethylamino)naphthalene (1), a hindered and exceptionally basic aniline that finds numerous applications as a basic catalyst or reagent due to its legendary lack of nucleophilicity. [2,3] Strong electrophiles interact weakly, if at all, with the amine nitrogens, and very few examples are known where stable bonds to nitrogen can be formed between 1 and electrophilic groups larger than hydrogen. [2,[4][5][6][7] Among these exceptional cases, cyclic boronium structures 2 and 3 are relatively stable because the subunits BH 2 and BF 2 have minimal steric requirements.…”

“…Aside from the structural features of 8a, the chemoselectivity of its formation also deserves attention. In view of earlier reports that strong electrophiles attack the aromatic system of 1 [3] or abstract hydride from one of the N-methyl groups, [3a, 31] it is quite intriguing that the reaction between 1 and 5a proceeds to form 8a, the most hindered of all plausible products. As evidenced by the electrophilic borylations (Table 1), the steric hindrance of 8a is responsible for extraordinary reactivity compared to less hindered boronium salts such as 14.…”