239075-02-6Relevant articles and documents
Synthesis of 2,3-Dihydrothieno[2,3-b]-1,4-dithiine, 2,3-Dihydrothieno-[3,2-b]-1,4-oxathiine, 2,3-Dihydrothieno[2,3-b]-1,4-oxathiine and Their Transformation into Corresponding End-Capped Oligomers
Hellberg, Jonas,Remonen, Tommi,Allared, Fredrik,Slaett, Johnny,Svensson, Mats
, p. 2199 - 2205 (2003)
Three new heterocyclic parent compounds, 2,3-dihydrothieno[2,3-b][1,4]dithiine (TDT), 2,3-dihydrothieno[3,2-b][1,4]oxathiine (TOT), and 2,3-dihydrothieno[2,3-b][1,4]oxathiine, have been synthesized by acid-catalyzed transformations starting from 3-methoxy
Iridium-bipyridine periodic mesoporous organosilica catalyzed direct C-H borylation using a pinacolborane
Maegawa, Yoshifumi,Inagaki, Shinji
supporting information, p. 13007 - 13016 (2016/01/09)
Heterogeneous catalysis for direct C-H borylation of arenes and heteroarenes in the combination of iridium (Ir) complex fixed on periodic mesoporous organosilica containing bipyridine ligands within the framework (Ir-BPy-PMO) and pinacolborane (HBpin) is reported. Ir-BPy-PMO showed higher catalytic activity toward the borylation of benzene with inexpensive HBpin compared to expensive bis(pinacolato)diboron (B2pin2). The precatalyst could be handled without the use of a glove box. The catalyst was easily recovered from reaction mixtures by simple filtration under air. The recovered catalyst still showed good catalytic activity for at least three more times for the borylation of benzene. A variety of arenes and heteroarenes were successfully borylated with high boron efficiency by Ir-BPy-PMO using HBpin, whereas almost no activity was observed for borylation of some heteroarenes with B2pin2. The system using Ir-BPy-PMO and HBpin was also utilized in syntheses of multi-boronated thiophene-based building blocks containing ladder-, acenefused-, and fused-thiophene skeletons. The combination of a stable and reusable solid catalyst and inexpensive HBpin is expected to be superior to conventional approaches for the development of industrial applications.
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.
, 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.