856798-53-3Relevant academic research and scientific papers
Mechanistic studies into amine-mediated electrophilic arene borylation and its application in MIDA boronate synthesis
Bagutski, Viktor,Del Grosso, Alessandro,Carrillo, Josue Ayuso,Cade, Ian A.,Helm, Matthew D.,Lawson, James R.,Singleton, Paul J.,Solomon, Sophia A.,Marcelli, Tommaso,Ingleson, Michael J.
supporting information, p. 474 - 487 (2013/02/25)
Direct electrophilic borylation using Y2BCl (Y2 = Cl2 or o-catecholato) with equimolar AlCl3 and a tertiary amine has been applied to a wide range of arenes and heteroarenes. In situ functionalization of the ArBCl2 products is possible with TMS 2MIDA, to afford bench-stable and easily isolable MIDA-boronates in moderate to good yields. According to a combined experimental and computational study, the borylation of activated arenes at 20 C proceeds through an S EAr mechanism with borenium cations, [Y2B(amine)] +, the key electrophiles. For catecholato-borocations, two amine dependent reaction pathways were identified: (i) With [CatB(NEt 3)]+, an additional base is necessary to accomplish rapid borylation by deprotonation of the borylated arenium cation (σ complex), which otherwise would rather decompose to the starting materials than liberate the free amine to effect deprotonation. Apart from amines, the additional base may also be the arene itself when it is sufficiently basic (e.g., N-Me-indole). (ii) When the amine component of the borocation is less nucleophilic (e.g., 2,6-lutidine), no additional base is required due to more facile amine dissociation from the boron center in the borylated arenium cation intermediate. Borenium cations do not borylate poorly activated arenes (e.g., toluene) even at high temperatures; instead, the key electrophile in this case involves the product from interaction of AlCl3 with Y2BCl. When an extremely bulky amine is used, borylation again does not proceed via a borenium cation; instead, a number of mechanisms are feasible including via a boron electrophile generated by coordination of AlCl3 to Y2BCl, or by initial (heteroarene)AlCl3 adduct formation followed by deprotonation and transmetalation.
A New Borylation Method for Alkylbenzene and Polystyrene
Paetzold, Peter,Hoffmann, Juergen
, p. 3724 - 3733 (2007/10/02)
The borylation of alkylbenzenes by Hal2BH (Hal = F, Cl, Br) gives H2 and a mixture of m- and p-alkyl(dihaloboryl)benzenes.In the case of bulky alkyl groups, such as isopropyl, tert-butyl, these are partially split off as R - H and RBHal2.The phenyl groups in polystyrene-divinylbenzene copolymers undergo borylation with Br2BH in a 55percent yield.
