Brian J. Frost

Aqueous and biphasic nitrile hydration catalyzed by a recyclable Ru(II) complex under atmospheric conditions

[RuCl2(PTA)4] (PTA = 1,3,5-triaza-7-phosphaadamantane) was found to be a highly active catalyst for aqueous phase nitrile hydration at 100 °C in air. Near quantitative conversion of aromatic, alkyl, and vinyl nitriles to their corresponding amides was observed. The reaction tolerated ether, hydroxyl, nitro, bromo, formyl, pyridyl, benzyl, alkyl, and olefinic functional groups. Some amides were isolated by simple decantation from the aqueous phase catalyst. Catalyst loading down to 0.001 mol% was examined with turnover numbers as high as 22000 observed. The catalyst was stable for weeks in solution and could be reused more than five times without significant loss of activity.

Hemilabile β-aminophosphine ligands derived from 1,3,5-triaza-7-phosphaadamantane: application in aqueous ruthenium catalyzed nitrile hydration.

A series of β-aminophosphines derived from 1,3,5-triaza-7-phosphaadamantane (PTA) are described. PTA-CHPhNHPh (1), PTA-CH(p-C(6)H(4)OCH(3))NHPh (2), and PTA-CPh(2)NHPh (3) were prepared in good yield (62-77%) by reaction of lithiated PTA with the corresponding imine followed by hydrolysis. Compounds 1 and 2 were synthesized as pairs of diastereomers which were separated by successive recrystallization from THF/hexane. Compounds 1-3 are somewhat soluble in water (S(25)(o) = 4.8 (1), 4.9 (2), 2.7 (3) g/L). Upon coordination to Ru(II) arene centers both monodentate (κ(1)-P) [RuCl(2)(η(6)-toluene)(1-3)] and bidentate (κ(2)-P,N) [RuCl(η(6)-toluene)(1-3)]Cl coordination modes were observed. Ru(II) arene complexes 4-6 exhibited hemilabile behavior transitioning between κ(1)-P and κ(2)-P,N coordination upon change in solvent or addition of a coordinating ligand such as Cl(-) or CH(3)CN. Complexes (4-6) were found to be active air stable catalysts for the aqueous phase hydration of various nitriles with TOF up to 285 h(-1) and TON of up to 97,000 observed.

The Suzuki Reaction in Aqueous Media Promoted by P, N Ligands

The synthesis and structure of palladium complexes of trisubstituted PTA derivatives, PTAR3, are described. Water-soluble phosphine ligands 1,3,5-triaza-7-phosphaadmantane (PTA), tris(aminomethyl)phosphine trihydrobromide, tri(aminomethyl) phosphine, 3,7-dimethyl-1,5,7-triaza-3-phosphabicyclo[3,3,1]nonane (RO-PTA), 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA), lithium 1,3,5-triaza-7-phosphaadamantane-6-carboxylate (PTA-CO2Li), 2,4,6-triphenyl-1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane, and 2,4,6-triphenyl-1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane were used as ligands for palladium catalyzed Suzuki reactions in aqueous media. RO-PTA in combination with palladium acetate or palladium chloride was the most active catalyst for Suzuki cross coupling of aryl bromides and phenylboronic acid at 80 °C in 1:1 water:acetonitrile. The activity of Pd(II) complexes of RO-PTA is comparable to PPh2(m-C6H4SO3Na) (TPPMS) and P(m-C6H4SO3Na)3 (TPPTS) and less active than tri(4,6-dimethyl-3-sulfonatophenyl)phosphine trisodium salt (TXPTS). Activated, deactivated, and sterically hindered aryl bromides were examined, with yields ranging from 50% to 90% in 6 h with 5% palladium precatalyst loading. X-ray crystal structures of (RO-PTA)PdCl2, (PTAR3)2PdCl2 (R = Ph, p-tert-butylC6H5), and PTAR3 (R = p-tert-butylC6H5) are reported.

Synthesis and Photoisomerization of Substituted Dibenzofulvene Molecular Rotors

The synthesis, spectral and structural characterization, and photoisomerization of a family of 2-substituted dibenzofulvene molecular actuators based on (2,2,2-triphenylethylidene)fluorene (TEF) are reported. The 2-substituted species investigated are nitro (NTEF), cyano (CTEF), and iodo (ITEF). X-ray structures of these three compounds and three intermediates were determined to assign alkene configuration and investigate the effects of the 2-substituents on steric gearing. The addition-elimination reaction of Z-9 with trityl anion to form Z-10 proceeded with complete retention of configuration. Rates of photoisomerization were measured at irradiation wavelengths between 266-355 nm in acetonitrile/dioxane solutions at room temperature. Photoisomerization quantum yields (φ) were calculated by means of a mathematical model that accounts for a certain degree of photodecomposition in the cases of CTEF and ITEF. Quantum yields vary significantly with substituent, having maximum values of φ=0.26 for NTEF, 0.39 for CTEF, and 0.50 for ITEF. NTEF is photochemically robust and has a large quantum yield for photoisomerization in the near-UV, making it a particularly promising drive rotor moiety for light-powered molecular devices.

Highly efficient conversion of terpenoid biomass to jet-fuel range cycloalkanes in a biphasic tandem catalytic process

The demand for bio-jet fuels to reduce carbon emissions is increasing substantially in the aviation sector, while the scarcity of high-density jet fuel components limits the use of bio-jet fuels in high-performance aircrafts compared with conventional jet fuels. Herein, we report a novel biphasic tandem catalytic process (biTCP) for synthesizing cycloalkanes from renewable terpenoid biomass, such as 1,8-cineole. Multistep tandem reactions, including C–O ring opening by hydrolysis, dehydration, and hydrogenation, were carried out in the “one-pot” biTCP. 1,8-Cineole was efficiently converted to p-menthane at high yields (>99%) in the biTCP under mild reaction conditions. The catalytic reaction mechanism is discussed.

Properties and Reactions of Organosilanes and Organogermanes Containing the Potentially Bidentate (X(CH2)n)2N‐Group

Compounds in the series R3SiN[(CH2)nX]2 (R = (CH3)2H, (CH3)2Cl, and CH3ClH), R2Si[N((CH2)nX)2]2 (R = (CH3)2, C6H5H, and C6H5Cl), R3GeN(CH2X)2 (R = (CH3)2Cl and (C6H5)2Cl), and Cl2Sn[N((CH2)3X)2]2, for X = N(CH3)2, n = 3; and OCH3, n = 2, have been prepared and characterized by 1H, 13C and 29Si NMR spectroscopy, and by elemental analyses. For all the compounds studied, the terminal N(CH3)2 and OCH3 groups appear not to coordinate to the central atom. The product C6H5Si{N[(CH2)2OCH3]2}2B[3,5‐(CF3)2C6H3]4, obtained from a reaction between C6H5HSi{N[(CH2)2OCH3]2}2 and (C6H5)3CB[3,5‐(CF3)2C6H3]4, should contain a silylium ion, but because of the suspected presence of a small quantity of silyl radical, has thus far eluded definitive characterization.

Unusual Water-Soluble Imino Phosphine Ligand: Enamine and Imine Derivatives of 1,3,5-Triaza-7-phosphaadamantane (PTA)

A series of water-soluble and air-stable E-enamine derivatives of 1,3,5-triaza-7-phosphaadamantane (PTA), PTA═C(R)NH2, 1-4, are reported along with data on E-Z isomerization and tautomerization to the imine form (PTA-CR═NH). Reaction of 1,3,5-triaza-7-phosphaamantane-6-yl lithium, PTA-Li, with aromatic nitriles afforded E-enamine derivatives of PTA in good yield (49-91%). Phosphines 1-4 are stable toward water and air, and do not appear to isomerize or tautomerize, unless coordinated to a metal or oxidized. The corresponding oxides, O═PTA═C(R)NH2 (5-8), were observed as ∼55/45 mixtures of E and Z isomers. Kinetic data on the E-Z isomerization is reported. Upon coordination of 1-4 to W(CO)4(pip)2, a κ1- P enamine is formed, [W(CO)4(pip)(κ1- P-PTA═CRNH2)]. Enamine-imine tautomerization of the metal bound phosphine was observed resulting in κ2- P, N imine complexes, [W(CO)4(κ2- P, N-PTA-CR═NH)], 9-12. The crystal structures of the κ1- P enamine 11a, κ2- P, N imine 9 and 12, phosphines 1 and 3, as well as phosphine oxide 8a were obtained. DFT calculations on the various isomers of the phosphines and phosphine oxides are also reported.

Solid State Structure of cis-[W(CO)4(pip)(PPh3)]

AbstractThe solid state structure of cis-[W(CO)4(PPh3)(pip)] (1) was determined by X-ray crystallography. cis-[W(CO)4(PPh3)(pip)] was synthesized by reaction of PPh3 with cis-[W(CO)4(pip)2] and isolated as yellow crystals. Compound 1 crystalized in the monoclinic space group P21/c and was found to have a distorted octahedral geometry. The P–W–N angle was slightly more acute than expected, presumably due to an unusual N–H⋯π interaction.Graphical AbstractThe solid state structure of cis-[W(CO)4(PPh3)(pip)] (1) is described with an P–W–N angle slightly more acute than expected, presumably due to an N–H⋯π interaction.

CCDC 972792: Experimental Crystal Structure Determination

Related Article: Jesse S. Hyslop, Amanda R. Boydstun, Theron R. Fereday, Joanna R. Rusch, Jennifer L. Strunk, Christian T. Wall, Cecelia C. Pena, Nicholas L. McKibben, Jerry D. Harris, Aaron Thurber, Alex Punnoose, Jason Brotherton, Pamela Walker, Lloyd Lowe, Blake Rapp, Shem Purnell, William B. Knowlton, Seth M. Hubbard, Brian J. Frost|2015|Mat.Sci.Semicond.Proc.|38|278|doi:10.1016/j.mssp.2015.04.001