269410-06-2Relevant articles and documents
Cross-Coupling through Ag(I)/Ag(III) Redox Manifold
Demonti, Luca,Mézailles, Nicolas,Nebra, Noel,Saffon-Merceron, Nathalie
supporting information, p. 15396 - 15405 (2021/10/12)
In ample variety of transformations, the presence of silver as an additive or co-catalyst is believed to be innocuous for the efficiency of the operating metal catalyst. Even though Ag additives are required often as coupling partners, oxidants or halide scavengers, its role as a catalytically competent species is widely neglected in cross-coupling reactions. Most likely, this is due to the erroneously assumed incapacity of Ag to undergo 2e? redox steps. Definite proof is herein provided for the required elementary steps to accomplish the oxidative trifluoromethylation of arenes through AgI/AgIII redox catalysis (i. e. CEL coupling), namely: i) easy AgI/AgIII 2e? oxidation mediated by air; ii) bpy/phen ligation to AgIII; iii) boron-to-AgIII aryl transfer; and iv) ulterior reductive elimination of benzotrifluorides from an [aryl-AgIII-CF3] fragment. More precisely, an ultimate entry and full characterization of organosilver(III) compounds [K]+[AgIII(CF3)4]? (K-1), [(bpy)AgIII(CF3)3] (2) and [(phen)AgIII(CF3)3] (3), is described. The utility of 3 in cross-coupling has been showcased unambiguously, and a large variety of arylboron compounds was trifluoromethylated via [AgIII(aryl)(CF3)3]? intermediates. This work breaks with old stereotypes and misconceptions regarding the inability of Ag to undergo cross-coupling by itself.
Chemoselective Rhodium-Catalyzed Borylation of Bromoiodoarenes under Mild Conditions
Varni, Anthony J.,Bautista, Michael V.,Noonan, Kevin J.T.
, p. 6770 - 6777 (2020/07/21)
A chemoselective rhodium-catalyzed borylation has been developed for the preparation of aryl boronate esters. The reaction proceeds under mild conditions with excellent selectivity for C-I bonds in bromoiodoarenes and exhibits broad functional group tolerance. This procedure can act as a complementary approach toward bifunctional arenes along with other metal-catalyzed borylations. Additionally, the reaction's utility in the preparation of monomers for metal-catalyzed cross-coupling polymerization is demonstrated.
Palladium(I) Dimer Enabled Extremely Rapid and Chemoselective Alkylation of Aryl Bromides over Triflates and Chlorides in Air
Kalvet, Indrek,Sperger, Theresa,Scattolin, Thomas,Magnin, Guillaume,Schoenebeck, Franziska
supporting information, p. 7078 - 7082 (2017/06/13)
Disclosed herein is the first general chemo- and site-selective alkylation of C?Br bonds in the presence of COTf, C?Cl and other potentially reactive functional groups, using the air-, moisture-, and thermally stable dinuclear PdI catalyst, [Pd(μ-I)PtBu3]2. The bromo-selectivity is independent of the substrate and the relative positioning of the competing reaction sites, and as such fully predictable. Primary and secondary alkyl chains were introduced with extremely high speed (5 min reaction time) at room temperature and under open-flask reaction conditions.
Radical Metal-Free Borylation of Aryl Iodides
Pinet, Sandra,Liautard, Virginie,Debiais, Mégane,Pucheault, Mathieu
, p. 4759 - 4768 (2017/10/03)
A simple metal-free borylation of aryl iodides mediated by a fluoride sp 2 -sp 3 diboron adduct is described. The reaction conditions are compatible with various functional groups. Electronic effects of substituents do not affect the borylation while steric hindrance does. The reaction proceeds via a radical mechanism in which pyridine serves to stabilize the boryl radicals, generated in situ.
Lewis Acid–Base Interaction-Controlled ortho-Selective C?H Borylation of Aryl Sulfides
Li, Hong Liang,Kuninobu, Yoichiro,Kanai, Motomu
supporting information, p. 1495 - 1499 (2017/02/05)
An iridium/bipyridine-catalyzed ortho-selective C?H borylation of aryl sulfides was developed. High ortho-selectivity was achieved by a Lewis acid–base interaction between a boryl group of the ligand and a sulfur atom of the substrate. This is the first example of a catalytic and regioselective C?H transformation controlled by a Lewis acid–base interaction between a ligand and a substrate. The C?H borylation reaction could be conducted on a gram scale, and with a bioactive molecule as a substrate, demonstrating its applicability to late-stage regioselective C?H borylation. A bioactive molecule was synthesized from an ortho-borylated product by converting the boryl and methylthio groups of the product.
One-pot Suzuki coupling of aromatic amines via visible light photocatalyzed metal free borylation using t-BuONO at room temperature
Ahammed, Sabir,Nandi, Shiny,Kundu, Debasish,Ranu, Brindaban C.
, p. 1551 - 1554 (2018/03/29)
A convenient and efficient metal free borylation of aromatic amines has been achieved using tertiary butyl nitrite and B2Pin2 (bis(pinacolato)diborane) under irradiation with blue LED light at room temperature. This protocol has been successfully extended to subsequent Suzuki coupling in the same pot. Thus a series of functionalized aryl boronates and biaryls are obtained in high yields in a shorter reaction period starting from relatively cheap aryl amines in one-pot avoiding isolation of potentially unstable and hazardous intermediates.
Regioselective electrophilic borylation of haloarenes
Del Grosso, Alessandro,Ayuso Carrillo, Josue,Ingleson, Michael J.
supporting information, p. 2878 - 2881 (2015/02/19)
Haloarenes undergo direct borylation using amine:BCl3:AlCl3 in the ratio of 1:1:2. After esterification the pinacol boronate esters are isolated in good yield with regioselectivity controlled by steric and electronic effects.
Use of 2-bromophenylboronic esters as benzyne precursors in the Pd-catalyzed synthesis of triphenylenes
Garcia-Lopez, Jose-Antonio,Greaney, Michael F.
supporting information, p. 2338 - 2341 (2014/05/20)
ortho-Substituted aryl boronates are introduced as aryne precursors for transition-metal-catalyzed transformations. On treatment with tBuOK and Pd(0), metal-bound aryne intermediates are formed that undergo effective trimerization to form useful triphenylene compounds. For meta-substituted arynes, the 3:1 product ratio in favor of non-C3 symmetric material is indicative of a benzyne mechanism.
High-yield syntheses and reactivity studies of 1,2-diborylated and 1,2,4,5-tetraborylated benzenes
Seven, Oemer,Bolte, Michael,Lerner, Hans-Wolfram,Wagner, Matthias
, p. 1291 - 1299 (2014/04/03)
Treatment of 1,2-dibromobenzene (1,2-C6H4Br 2) or 1,2,4,5-tetrabromobenzene (1,2,4,5-C6H 2Br4) with 2 equiv or 4 equiv of n-BuLi in the presence of excess iso-propoxy(pinacol)borane ((i-PrO)Bpin) furnishes 1,2-C 6H4(Br)(Bpin) (1) or 1,4,2,5-C6H 2(Br)2(Bpin)2 (3) with excellent selectivity. The subsequent reaction of 1 or 3 with Mg turnings and more (i-PrO)Bpin gives the di- and tetraborylated benzenes 1,2-C6H4(Bpin) 2 (2) and 1,2,4,5-C6H2(Bpin)4 (4) in overall yields of about 65%. For the Grignard transformation step, it is essential to continuously add 1 equiv (1) or 2 equiv (3) of 1,2-dibromoethane as an entrainer over a period of 1 h. Compounds 1 and 2 have been transformed into the ortho-functionalized trihydroborates Li[1,2-C6H 4(Br)(BH3)] (Li[7]) and Li[1,2-C6H 4(Bpin)(BH3)] (Li[8]) by means of 1 equiv of Li[AlH 4]. Using 3 equiv of Li[AlH4], 2 can also be converted into the ditopic lithium trihydroborate Li2[1,2-C6H 4(BH3)2] (Li2[9]); even the tetratopic derivative Li4[1,2,4,5-C6H2(BH 3)4] (Li4[10]) is accessible from 4 and 4 equiv of Li[AlH4]. The compounds Li[7], Li[8], Li2[9], and Li4[10] have been crystallographically characterized as ether solvates, but still show Ar-BH3-η2-Li interactions as the dominant mode of coordination. In the cases of Li2[9] and Li 4[10] an intricate three-dimensional network and a zigzag polymer, respectively, are established by the contact ion pairs in the crystal lattice.
Borylation using group IV metallocene under mild conditions
Marciasini, Ludovic D.,Vaultier, Michel,Pucheault, Mathieu
, p. 1702 - 1705 (2014/03/21)
A borylation reaction of aromatic diazonium salts has been optimized using titanocene and zirconocene derivatives as catalysts. The reaction employs diisopropylaminoborane as a borylating agent and proceeds smoothly at room temperature to provide arylboronates after methanolysis and transesterification with pinacol. The reaction mechanism has been found to proceed via a radical pathway.
