Jeffrey M. Stryker

Highly Chemoselective Catalytic Hydrogenation of Unsaturated Ketones and Aldehydes to Unsaturated Alcohols Using Phosphine-Stabilized Copper(I) Hydride Complexes

Abstract A base metal hydrogenation catalyst composed of the phenyldimethylphosphine-stabilized copper(I) hydride complex provides for the highly chemoselective hydrogenation of unsaturated ketones and aldehydes to unsaturated alcohols, including the regioselective 1,2-reduction of α,β-unsaturated ketones and aldehydes to allylic alcohols. The active catalyst can be derived in situ by phosphine exchange using commercial [(Ph 3 P)CuH] 6 or from the reaction of copper(I) chloride, sodium tert -butoxide, and dimethylphenylphosphine under hydrogen. The catalyst derived from 1,1,1-tris(diphenylphosphinomethyl)ethane is mechanistically interesting but less synthetically useful.

Phosphine Effects in the Copper(I) Hydride-Catalyzed Hydrogenation of Ketones and Regioselective 1,2-Reduction of α,β-Unsaturated Ketones and Aldehydes. Hydrogenation of Decalin and Steroidal Ketones and Enones

Abstract The stereoselectivity and regioselectivity of the catalytic hydrogenation of ketones and α,β-unsaturated ketones and aldehydes using soluble copper(I) hydride catalysts have been investigated as a function of the ancillary phosphine ligand. While a relatively narrow range of aryldialkylphosphine ligands produce active hydrogenation catalysts, some ligands provide higher selectivity for 1,2-reduction of acyclic unsaturated carbonyl substrates than observed using the previously reported dimethylphenylphosphine-stabilized catalyst. The synthetic utility of this class of hydridic hydrogenation catalysts is illustrated by the hydrogenation of decalin and steroidal ketones and enones, the latter giving allylic alcohols with high selectivity.

Computational and Experimental Study of the Structure, Binding Preferences, and Spectroscopy of Nickel(II) and Vanadyl Porphyrins in Petroleum

We present a computational exploration of five- and six-coordinate Ni(II) and vanadyl porphyrins, including prediction of UV-vis spectroscopic behavior and metalloporphyrin structure as well as determination of a binding energy threshold between strongly bound complexes that have been isolated as single crystals and weakly bound ones that we detect by visible absorption spectroscopy. The excited states are calculated using the tandem of the time-dependent density functional theory (TD-DFT) and the conductor-like polarizable continuum model (CPCM). The excited-state energies in chloroform solvent obtained by using two density functionals are found to correlate linearly with the experimental Soret and alpha-band energies for a known series of five-coordinate vanadyl porphyrins. The established linear correction allows simulation of the excited states for labile octahedral vanadyl porphyrins that have not been isolated and yields Soret and alpha-band bathochromic shifts that are in agreement with our UV-vis spectroscopic results. The PBE0 and PW91 functionals in combination with DNP basis set perform best for both structure and binding energy prediction. The reactivity preferences of Ni(II) and vanadyl porphyrins toward aromatic fragments of large petroleum molecules are explored by using the density functional theory (DFT). Analysis of electrostatic potentials and Fukui functions matching shows that axial coordination and hydrogen bonding are the preferred aggregation modes between vanadyl porphyrins and nitrogen-containing heterocycle fragments. This investigation improves our understanding on the cause for broadening of the Ni and V porphyrin Soret band in heavy oils. Our findings can be useful for the development of metals removal methods for heavy oil upgrading.

Selective Mono-and 1,2-Difunctionalisation of Cyclopentene Derivatives via Mg and Cu Intermediates

A single Br/Mg exchange of 1,2-dibromocyclopentene with iPrMgCl LiCl provides the corresponding beta-bromocyclopentenylmagnesium reagent, which can then be reacted with various electrophiles (yields: 65-82 %). In the presence of a secondary alkylmagnesium halide and Li2CuCl4 (2 mol %), these 2-bromoalkenylmagnesium compounds undergo bromine substitution and can then further react with electrophiles to give 1,2-difunctionalised cyclopentenes (63-79 %). The mechanism of this process is discussed.

Cobalt-Mediated η5-Pentadienyl/Alkyne [5 + 2] Cycloaddition. Synthesis and Characterization of Unbridged η2,η3-Coordinated Cycloheptadienyl Complexes

A general new metal-mediated [5 + 2] cycloaddition reaction of η5-pentadienyl cobalt complexes and alkynes is reported, the first such cycloaddition reaction to provide controlled incorporation of 1 equiv of alkyne. The reaction of terminally substituted pentadienyl complexes proceeds thermally under exceptionally mild conditions, affording cycloheptadienyl complexes cleanly and in high yield. As a consequence of the unusually low kinetic barrier to the cycloaddition, reactions with acetylene at low temperature produce the cycloheptadienyl ring system exclusively as the η2,η3-isomer, an unprecedented coordination mode for unbridged seven-membered ring complexes. Isomerization of the kinetic product to the fully conjugated η5-cycloheptadienyl isomer is observed quantitatively upon heating. Disubstituted alkynes, as represented by 2-butyne, proceed through the η2,η3-intermediate to the thermodynamic η5-complex, but the rate of initial alkyne incorporation is attenuated to the extent that isomerization is co...

Unexpected Michael Additions on the Way to 2.3,8.9-Dibenzanthanthrenes with Interesting Structural Properties.

The synthesis and properties of a new polycyclic aromatic hydrocarbon containing eight annulated rings and based on the anthanthrene core is described. An unexpected, nucleophile-dependent Michael addition to a dibenzanthanthrene-1,7-dione is found, giving a product with three triisopropylsilylacetylene units and a remarkable solid-state structure (as determined by X-ray crystallography).

A Density Functional Theory Investigation of the Cobalt-Mediated η5-Pentadienyl/Alkyne [5+2] Cycloaddition Reaction: Mechanistic Insight and Substituent Effects

Alkyl-substituted η(5)-pentadienyl half-sandwich complexes of cobalt have been reported to undergo [5+2] cycloaddition reactions with alkynes to provide η(2),η(3)-cycloheptadienyl complexes under kinetic control. DFT studies have been used to elucidate the mechanism of the cyclization reaction as well as that of the subsequent isomerization to the final η(5)-cycloheptadienyl product. The initial cyclization is a stepwise process of olefin decoordination/alkyne capture, C-C bond formation, olefin arm capture, and a second C-C bond formation; the initial decoordination/capture step is rate-limiting. Once the η(2),η(3)-cycloheptadienyl complex has been formed, isomerization to η(5)-cycloheptadienyl again involves several steps: olefin decoordination, β-hydride elimination, reinsertion, and olefin coordination; also here the initial decoordination step is rate limiting. Substituents strongly affect the ease of reaction. Pentadienyl substituents in the 1- and 5-positions assist pentadienyl opening and hence accelerate the reaction, while substituents at the 3-position have a strongly retarding effect on the same step. Substituents at the alkyne (2-butyne vs. ethyne) result in much faster isomerization due to easier olefin decoordination. Paths involving triplet states do not appear to be competitive.

Steroid-Derived Naphthoquinoline Asphaltene Model Compounds: Hydriodic Acid Is the Active Catalyst in I2-Promoted Multicomponent Cyclocondensation Reactions

A multicomponent cyclocondensation reaction between 2-aminoanthracene, aromatic aldehydes, and 5-α-cholestan-3-one has been used to synthesize model asphaltene compounds. The active catalyst for this reaction has been identified as hydriodic acid, which is formed in situ from the reaction of iodine with water, while iodine is not a catalyst under anhydrous conditions. The products, which contain a tetrahydro[4]helicene moiety, are optically active, and the stereochemical characteristics have been examined by VT-NMR and VT-CD spectroscopies, as well as X-ray crystallography.