37737-62-5Relevant academic research and scientific papers
Catalyzed hydroboration of nitrostyrenes and 4-vinylaniline: A mild and selective route to aniline derivatives containing boronate esters
Vogels, Christopher M.,Decken, Andreas,Westcott, Stephen A.
, p. 2419 - 2422 (2007/10/03)
Transition metal catalyzed reactions of catecholborane (HBcat; cat = 1,2-O2C6H4) with β-nitrostyrene and 3-nitrostyrene lead to products derived from competing hydrogenation and hydroboration of the alkene unit along with reduction of the nitro group. Hydroboration of 4-vinylaniline gave regioselective formation of either the branched or the linear organoboronate ester depending upon the catalyst precursors (i.e., RhCl(PPh3)3 or Rh(acac)(dppe) vs [Cp*IrCl2]2) used to facilitate this reaction. Hydroboration products were converted to air-stable primary amines by addition of pinacol.
Phosphine promoted substituent redistribution reactions of B-chlorocatechol borane: Molecular structures of ClBcat, BrBcat and L·ClBcat (cat = 1,2-O2C6H4; L = PMe3, PEt3, PBut3,
Coapes,Souza,Fox,Batsanov,Goeta,Yufit,Leech,Howard,Scott,Clegg,Marder
, p. 1201 - 1209 (2007/10/03)
In order to evaluate the potential for side reactions when using B-chlorocatechol borane (ClBcat) in stoichiometric or catalytic transformations involving metal phosphine complexes, we examined the interaction between ClBcat and a series of PR3
Metal-catalyzed hydroboration and diboration of thiocarbonyls and vinyl sulfides
Carter, Charles A.G.,Vogels, Christopher M.,Harrison, Daniel J.,Karen,Gagnon,Norman, David W.,Langler, Richard F.,Baker, R. Thomas,Westcott, Stephen A.
, p. 2130 - 2132 (2008/10/08)
α-Thioboronate esters are obtained directly in high yield and selectivity from metal-catalyzed additions of B-X bonds (X = H, B) to thiocarbonyl compounds and vinyl sulfides.
Boron-boron bond oxidative addition to rhodium(I) and iridium(I) centres
Clegg, William,Lawlor, Fiona J.,Marder, Todd B.,Nguyen, Paul,Norman, Nicholas C.,Orpen, A. Guy,Quayle, Michael J.,Rice, Craig R.,Robins, Edward G.,Scott, Andrew J.,Souza, Fabio E. S.,Stringer, Graham,Whittell, George R.
, p. 301 - 309 (2007/10/03)
The reaction between the diborane(4) compound B2(1,2-O2C6H4)2 and either of the rhodium(I) complexes [RhCl(PPh3)3] or [{Rh(μ-Cl)(PPh3)2}2] afforded the colourless rhodium(III) bis(boryl) species [RhCl(PPh3)2-{B(1,2-O2C6H 4)}2]. Similar reactions have been carried out with the diborane(4) compounds B2(1,2-O2-4-ButC6H3) 2, B2(1,2-O2-3,5-But2C 6H2)2, B2(1,2-O2-3-MeC6H3)2, B2(1,2-O2-4-MeC6H3)2, B2(1,2-O2-3-MeOC6H3)2, B2(1,2-S2C6H4)2, B2(1,2-S2-4-MeC6H3)2 and B2[R,R-1,2-O2CH(CO2Me)CH(CO 2Me)]2 affording analogous rhodium complexes all of which have been characterised spectroscopically. The complexes derived from the reactions with B2(1,2-O2C6H4)2 and B2(1,2-O2-3-MeC6H3)2 have also been characterised by X-ray crystallography, the structures comprising a five-co-ordinate rhodium centre with a square-based-pyramidal geometry in which the apical site is occupied by a boryl group and the phosphines are mutually trims in basal positions. Reactivity studies have also been carried out for [RhCl(PPh3)2{B(1,2-O2C6H 4)}2]. Hydrolysis or alcoholysis with catechol afforded [RhH2Cl(PPh3)3] and either B2(1,2-O2C6H4)2(μ-O) or B2(1,2-O2C6H4)3 and addition of the phosphines PMe3, PEt3 and PMe2Ph afforded the new bis(boryl) compounds cis,mer-[RhCl(PMe3)3{B(1,2-O2C 6H4)}2], [RhCl(PEt3)2-{B(1,2-O2C6H 4)}2] and cis,mer-[RhCl(PMe2Ph)3{B(1,2-O2C 6H4)}2], the PEt3 complex having been characterised by X-ray crystallography and shown to be similar to the PPh3 complex. The iridium analogue [IrCl(PEt3)2-{B(1,2-O2C6H 4)}2] was also prepared from the reaction between [IrCl(PEt3)3] and B2(1,2-O2C6H4)2 and shown by X-ray crystallography to be isomorphous with the rhodium complex. Reactions between [RhCl(PPh3)2-{B(1,2-O2C6H 4)}2] and the phosphines PPri3, P(C6H11)3, 1,2-bis(diphenylphosphino)ethane (dppe) and 1,2-bis(dicyclohexylphosphino)ethane (dcpe) are also described although these do not result in new rhodium boryl complexes. The reaction between [{RhCl(dppe)}2] and B2(1,2-O2C6H4)2 afforded a compound tentatively assigned as [Rh(dppe)2{B(1,2-O2C6H4)}] with analogous compounds being formed with the diborane(4) compounds B2(1,2-O2-3-MeC6H3)2 and B2(1,2-O2-4-MeC6H3)2. Finally, the reaction between [Rh(PMe3)4]Cl and the diborane(4) compound B2(1,2-O2C6H4)2 is described which affords cis,mer-[RhCl(PMe3)3{B(1,2-O2C 6H4)}2]. Analogous reactions with B2(1,2-O2-3,5-But2C 6H2)2, B2(1,2-O2-3-MeC6H3)2 and B2[R,R-1,2-O2CH(CO2Me)CH-(CO 2MeJ]2 afforded similar products.
Nucleophile promoted degradation of catecbolborane: Consequences for transition metal-catalyzed hydroborations
Westcott, Stephen A.,Blom, Henk P.,Marder, Todd B.,Baker, R. Thomas,Calabrese, Joseph C.
, p. 2175 - 2182 (2008/10/08)
Reactions of tertiary phosphines or phosphinorhodium complexes with catecholborane (HB(cat)) give boron-substituent redistribution products. While sterically compact phosphines (PMe3, PEt3, PMe2Ph) react with 1 equiv of HBcat to give [(PR3)2BH2]+[B(cat) 2]-, bulkier phosphines (PPh3, PPri3, PCy3) afford phosphine-boranes H3B·PR3 and tris(catecholato)diboron, B2(cat)3. Reactions of HB(cat) with coordinatively saturated [RhH(DPPP)2] (DPPP = 1,3-bis(diphenylphosphino)propane) and [RhH(PMe3)4] afforded cationic species [RhH2(DPPP)2]+[B(cat)2]- and [RhH2(PMe3)4]+[B(cat) 2]- respectively, both of which are active catalyst precursors for addition of HB(cat) to 4-vinylanisole. These catalyzed hydroborations, however, gave significant amounts of BH3-derived products, arising from Rh-mediated HB(cat) degradation. The only catalyst precursors examined which did not lead to degradation of HB(cat) were rhodium(I) chloride complexes containing basic monodentate phosphines. Molecular structures of B2(cat)3 (3), [(PEt3)2BH2] [B(cat)2] (4b), and [RhH2(PMe3)4] [B(cat)2] (9) were determined by single crystal X-ray diffraction. Colorless crystals of 3 are monoclinic, P21/c (No. 14), with four molecules per unit cell of dimensions a = 12.922(5) A?, b = 12.245(2) A?, c = 10.784(8) A?, and β= 109.03°. Colorless crystals of 4b are monoclinic, P21/n (No. 14), with eight molecules per unit cell of dimensions a - 17.453(6) A?, b = 11.414(1) A?, c = 26.666(9) A?, and β = 95.17(2)°. Orange crystals of 9 are trigonal, P3221 (No. 154), with three molecules per unit cell of dimensions a = 13.222(1) A?, b = 13.222(1) A?, and c = 17.294(6) A?.
Reactions of catecholborane with wilkinson's catalyst: Implications for transition metal-catalyzed hydroborations of alkenes
Burgess, Kevin,Van Der Donk, Wilfred A.,Westcott, Stephen A.,Marder, Todd B.,Baker, R. Thomas,Calabrese, Joseph C.
, p. 9350 - 9359 (2007/10/02)
Reactions of catecholborane (HBO2C6H4) with RhCl(PPh3)3 (1) yield a variety of products depending on the B/Rh ratio, solvent, and temperature. Of particular relevance to catalyzed alkene hydroboration is degradation of HBO2C6H4 to B2(O2C6H4)3/'BH 3' and the dihydride RhH2Cl(PPh3)3 (3). The molecular structure of 3, determined by X-ray diffraction, has meridional phosphine ligands and cis hydrides. Catalyst systems formed from in situ addition of PPh3 to [Rh(μ-Cl)(COD)]2 (COD = 1,5-cyclooctadiene) are fundamentally different from Wilkinson's catalyst; RhCl(COD)(PPh3) forms initially, but the reaction of this with PPh3 is slow. Monitoring catalyzed hydroborations using Wilkinson's catalyst and catecholborane by multinuclear NMR spectroscopy, prior to oxidative workup, showed that alkylboranes were formed with some sterically hindered alkenes. With 2-methylbut-2-ene (24), for example, we observed significant quantities of disiamylborane, (CHMeCHMe2)2, formed via addition of 'BH3' to 24. When excess PPh3 was added to the catalyst system, however, the desired alkylboronate ester was formed in high yield. Partial oxidation of RhCl(PPh3)3 had a significant effect on product (and D-label) distributions. Detailed investigations of catalyzed additions of DBO2C6H4 to allylic silyl ethers CH2=C(Me)CRR′(OSitBuMe2) (R, R′ = H, Me) demonstrated that deuterium incorporation at the carbon bonded to boron in the primary alcohol product occurs only with freshly prepared Wilkinson's catalyst or when excess PPh3 is added to the oxidized catalyst. With freshly prepared Wilkinson's catalyst, addition of H2 (or D2) to these substrates is a significant competing reaction and appreciable catalytic formation of vinylboronate esters is also observed. The latter presumably arise via insertion of alkene into a Rh-B bond, followed by β-hydride elimination. Subsequent in situ addition of H2 (DH or D2) to these vinylboronate esters provides an alternative explanation to α-deuterium incorporation into the resulting primary alcohols.
