Showing papers on "Steric effects published in 2014"
TL;DR: It is shown that the metal-organic framework Fe2(dobdc) and its magnesium-diluted analogue, Fe0.1Mg1.9( dobdc), are able to activate the C-H bonds of ethane and convert it into ethanol and acetaldehyde using nitrous oxide as the terminal oxidant.
Abstract: Enzymatic haem and non-haem high-valent iron-oxo species are known to activate strong C-H bonds, yet duplicating this reactivity in a synthetic system remains a formidable challenge. Although instability of the terminal iron-oxo moiety is perhaps the foremost obstacle, steric and electronic factors also limit the activity of previously reported mononuclear iron(IV)-oxo compounds. In particular, although nature's non-haem iron(IV)-oxo compounds possess high-spin S = 2 ground states, this electronic configuration has proved difficult to achieve in a molecular species. These challenges may be mitigated within metal-organic frameworks that feature site-isolated iron centres in a constrained, weak-field ligand environment. Here, we show that the metal-organic framework Fe2(dobdc) (dobdc(4-) = 2,5-dioxido-1,4-benzenedicarboxylate) and its magnesium-diluted analogue, Fe0.1Mg1.9(dobdc), are able to activate the C-H bonds of ethane and convert it into ethanol and acetaldehyde using nitrous oxide as the terminal oxidant. Electronic structure calculations indicate that the active oxidant is likely to be a high-spin S = 2 iron(IV)-oxo species.
358 citations
TL;DR: A catalytic intermolecular C–H silylation of unactivated arenes that manifests very high regioselectivity through steric effects of substituents meta to a potential site of reactivity is reported.
Abstract: Regioselective C–H functionalization of arenes has widespread applications in synthetic chemistry. The regioselectivity of these reactions is often controlled by directing groups or steric hindrance ortho to a potential reaction site. Here, we report a catalytic intermolecular C–H silylation of unactivated arenes that manifests very high regioselectivity through steric effects of substituents meta to a potential site of reactivity. The silyl moiety can be further functionalized under mild conditions but is also inert toward many common organic transformations, rendering the silylarene products useful building blocks. The remote steric effect that we observe results from the steric properties of both the rhodium catalyst and the silane.
350 citations
TL;DR: The full mechanism of the hydroboration of CO2 by the highly active ambiphilic organocatalyst 1-Bcat-2-PPh2-C6H4 (Bcat = catecholboryl) was determined using computational and experimental methods.
Abstract: The full mechanism of the hydroboration of CO2 by the highly active ambiphilic organocatalyst 1-Bcat-2-PPh2–C6H4 (Bcat = catecholboryl) was determined using computational and experimental methods. The intramolecular Lewis pair was shown to be involved in every step of the stepwise reduction. In contrast to traditional frustrated Lewis pair systems, the lack of steric hindrance around the Lewis basic fragment allows activation of the reducing agent while moderate Lewis acidity/basicity at the active centers promotes catalysis by releasing the reduction products. Simultaneous activation of both the reducing agent and carbon dioxide is the key to efficient catalysis in every reduction step.
187 citations
TL;DR: This work shows that cobalt(II) catalysts supported by bulky β-diketiminate ligands have the appropriate kinetic selectivity to catalyze the isomerization of some simple 1-alkenes specifically to the 2-alkene as the less stable Z-isomer.
Abstract: The isomerization of simple terminal alkenes to internal isomers with Z-stereochemistry is rare, because the more stable E-isomers are typically formed. We show here that cobalt(II) catalysts supported by bulky β-diketiminate ligands have the appropriate kinetic selectivity to catalyze the isomerization of some simple 1-alkenes specifically to the 2-alkene as the less stable Z-isomer. The catalysis proceeds via an "alkyl" mechanism, with a three-coordinate cobalt(II) alkyl complex as the resting state. β-Hydride elimination and [1,2]-insertion steps are both rapid, as shown by isotopic labeling experiments. A steric model explains the selectivity through a square-planar geometry at cobalt(II) in the transition state for β-hydride elimination. The catalyst works not only with simple alkenes, but also with homoallyl silanes, ketals, and silyl ethers. Isolation of cobalt(I) or cobalt(II) products from reactions with poor substrates suggests that the key catalyst decomposition pathways are bimolecular, and lowering the catalyst concentration often improves the selectivity. In addition to a potentially useful, selective transformation, these studies provide a mechanistic understanding for catalytic alkene isomerization by high-spin cobalt complexes, and demonstrate the effectiveness of steric bulk in controlling the stereoselectivity of alkene formation.
168 citations
TL;DR: In this article, the role of Lewis and Bronsted sites in the dehydration of glycerol on niobium oxide and Na+-exchanged Niobium oxides was investigated using FTIR spectroscopy supported by DFT calculations.
Abstract: The role of Lewis and Bronsted sites in the dehydration of glycerol on niobium oxide and Na+-exchanged niobium oxide is investigated using FTIR spectroscopy supported by DFT calculations. Glycerol is impregnated on the catalysts at room temperature using an ex-situ method. Under high vacuum conditions, glycerol forms a stable multidentate alkoxy species through its primary hydroxyl groups with the Lewis sites. When coordinated this way, the primary C–O bonds are polarized, favoring dehydration in this position to form hydroxyacetone. In contrast, dehydration of the secondary alcohol group is kinetically favored over Bronsted acid sites in the absence of steric constraints. The primary product of this reaction, 1,3-propenediol, is further dehydrated to acrolein. When more than a monolayer of glycerol is impregnated on niobia, monoaromatic compounds are also formed on the surface upon heating.
153 citations
TL;DR: The factors governing selective Rh2(esp)2-catalyzed C–H amination of isoamylbenzene derivatives are investigated, where modification to both the nitrogen source, a sulfamate ester, and substrate are shown to impact isomeric product ratios.
Abstract: Predicting site selectivity in C-H bond oxidation reactions involving heteroatom transfer is challenged by the small energetic differences between disparate bond types and the subtle interplay of steric and electronic effects that influence reactivity. Herein, the factors governing selective Rh2(esp)2-catalyzed C-H amination of isoamylbenzene derivatives are investigated, where modification to both the nitrogen source, a sulfamate ester, and substrate are shown to impact isomeric product ratios. Linear regression mathematical modeling is used to define a relationship that equates both IR stretching parameters and Hammett σ(+) values to the differential free energy of benzylic versus tertiary C-H amination. This model has informed the development of a novel sulfamate ester, which affords the highest benzylic-to-tertiary site selectivity (9.5:1) observed for this system.
125 citations
TL;DR: The synthesis of a three-coordinate Pt-borane complex featuring a bidentate "LZ" (boryl)iminomethane (BIM) ligand is reported, showing the ability of the free BIM to effect bond activation reactions is contrasted with the behavior seen in the corresponding platinum-bound complexes.
Abstract: The synthesis of a three-coordinate Pt–borane complex featuring a bidentate “LZ” (boryl)iminomethane (BIM) ligand is reported. Unlike other LZ-type borane ligands featuring a single-donor buttress, the small bite angle enforced by the BIM ligand is shown to promote a significant metal–borane reverse-dative σ-interaction akin to multiply strapped metalloboratranes. The steric accessibility of the reactive Pt → B bond fostered by the BIM ligand allows for a rich reactivity profile toward small molecules that exploit metal–borane cooperative effects. The unligated (boryl)iminomethane BIM is also synthetically accessible and functions as a Frustrated Lewis Pair (FLP). The ability of the free BIM to effect bond activation reactions is contrasted with the behavior seen in the corresponding platinum-bound complexes.
112 citations
TL;DR: Experimental studies and computational results show that C-H bond cleavage is the rate-determining step of the current borylation reactions.
Abstract: Borylation of aliphatic C–H bonds in alkylamines and alkyl ethers to form primary aminoalkyl and alkoxyalkyl boronate esters and studies on the origin of the regioselectivity of these reactions are reported. The products of these reactions can be used directly in Suzuki–Miyaura cross-coupling reactions or isolated as air-stable potassium trifluoroborate salts. Selective borylation of the terminal C–H bond at the positions β to oxygen and nitrogen occurs in preference to borylation of the other terminal C–H bonds. Experimental studies and computational results show that C–H bond cleavage is the rate-determining step of the current borylation reactions. The observed higher reactivity of C–H bonds at the terminal position of ethylamines and ethers results from a combination of attractive Lewis acid–base and hydrogen-bonding interactions, as well as typical repulsive steric interactions, in the transition state. In this transition state, the heteroatom lies directly above the boron atom of one boryl ligand, c...
112 citations
TL;DR: In this article, the metal-free catalytic asymmetric hydrogenation and hydrosilylation using frustrated Lewis pairs (FLP) catalysts has been discussed, and the authors outline the recent important progress.
98 citations
TL;DR: In this article, the effect of methoxy functionalization of three N-heterocyclic carbene ligands was assessed using a variety of methods, and the steric environment of each carbene has been assessed in various coordination environments.
91 citations
TL;DR: In this article, a new type (heterogeneous) of frustrated Lewis pairs (FLP) was proposed for gold surfaces, which avoided tight adsorption of Lewis bases to gold surface via repulsion between nitrogen lone pair and the filled d-band electrons of the gold surface.
Abstract: Clean gold surface is inactive toward H2, however, computations, aided by experiments, reveal that gold surface could serve as a Lewis acid coupling with Lewis bases (e.g. imine and nitrile) to construct effective frustrated Lewis pairs (FLPs) to activate H2 and subsequently to achieve hydrogenation of small imines and nitriles. The Lewis base-coupled Au FLPs avoid tight adsorption of Lewis bases to gold surface via repulsion between nitrogen lone pair and the filled d-band electrons of the gold surface. This is different from the normal FLPs that use sterically demanding groups or a molecular scaffold to prevent formation of stable Lewis acid–base complexes. The enhanced reactivity of the gold surface toward H2 is due to the synergetic catalytic effects of Lewis acid (Au surface) and the coupled Lewis base (imine or nitrile), which is supported by projected density of states (PDOS) analyses. Among Cu, Ag and Au surfaces, Au surface exhibits such reactivity most significantly, because Au is much more electronegative than Cu and Ag. The study enriches the FLP chemistry by adding a new type (heterogeneous) of FLPs and reveals a new reaction mode for gold surface.
TL;DR: In this paper, a series of phosphinimino-amine-based complexes (HL1, HL2, HL3, HL4, HL5, HL6, HL7, HL8, HL9, HL10, HL11, HL12, HL13, HL14, HL15, HL16, HL17, HL18, HL19, HL20, HL21, HL22, HL23, HL24, HL25, HL26, HL27, HL28, HL29, HL30, HL31, HL32, HL33, HL
TL;DR: The syntheses of salts containing ligand-stabilized Ph3Sb( 2+) and Ph3Bi(2+) dications have been realized by in situ formation of Ph3Pn(OTf)2 (Pn=Sb or Bi) and subsequent reaction with OPPh3, dmap and bipy.
Abstract: The syntheses of salts containing ligand-stabilized Ph3Sb(2+) and Ph3Bi(2+) dications have been realized by in situ formation of Ph3Pn(OTf)2 (Pn=Sb or Bi) and subsequent reaction with OPPh3, dmap and bipy The solid-state structures demonstrate diversity imposed by the steric demands and nature of the ligands The synthetic method has the potential for broad application enabling widespread development of the coordination chemistry for Pn(V) acceptors
TL;DR: This novel method enables PC bond formation in a controlled fashion using white phosphorus as starting material and gives access to non-symmetrical disubstituted bicyclic tetraphosphorus compounds.
Abstract: Reacting white phosphorus (P4) with sterically encumbered aryl lithium reagents (aryl=2,6-dimesitylphenyl or 2,4,6-tBu3C6H2) and B(C6F5)3 gives the unique, isolable Lewis acid stabilized bicyclo[1.1.0]tetraphosphabutane anion. Subsequent alkylation of the nucleophilic site of the RP4 anion gives access to non-symmetrical disubstituted bicyclic tetraphosphorus compounds. This novel method enables PC bond formation in a controlled fashion using white phosphorus as starting material.
TL;DR: The regioselectivity in nucleophile trapping is investigated with arynes generated directly from bis-1,3-diynes, which is the consequence of both the unfavorable steric interaction between the incoming nucleophile and the nearby substituent and the inherent electronic bias induced by different substituents on the aryne.
TL;DR: X-ray crystallography reveals exclusive selectivity of the acyclic Schiff dibasic form of the ligands over the heterocyclic analogues, and this selectivity is found to be insensitive to the oxidation state of cobalt.
Abstract: The present report describes the syntheses, characterizations, crystal structures and study of the phenoxazinone synthase activity of two peroxo-bridged dicobalt(III) complexes, [Co2(L1)2(μ-O2)](ClO4)4·2CH3CN (1) and [Co2(L2)2(μ-O2)](ClO4)4 (2), and three mononuclear cobalt(II) complexes, [Co(L3)(CH3CN)](ClO4)2 (3), [Co(L4)(H2O)](ClO4)2 (4) and [Co(L5)(H2O)](ClO4)2 (5), derived from the pentadentate ligands L1–L5, which are the 1 : 2 condensation products of triamines and 2-acetylpyridine or 2-pyridinecarboxaldehyde (6-methyl-2-pyridinecarboxaldehyde). X-ray crystallography reveals exclusive selectivity of the acyclic Schiff dibasic form of the ligands over the heterocyclic analogues, and this selectivity is found to be insensitive to the oxidation state of cobalt. Other first row transition metals have been characterized in either form of the ligands in their complexes but it is specific for cobalt established in the present study. The pronounced effect of the methyl substitutions is observed from their crystal structures; substitution at imine-C does not have any significant influence on the peroxo-bridging but substitution at sixth position of pyridyl ring prevents the formation of peroxo-bridging, and both the steric and electronic factors play vital roles on such chemical diversity. All the complexes show the phenoxazinone synthase mimicking activity and the comparative catalytic activity has been explored. Although electrochemical behaviors of all the complexes are very similar, their relative catalytic activity mimicking the function of phenoxazinone synthase arises from the electronic and steric factors of the methyl substitution.
TL;DR: In this article, a new Al/P FLP was obtained with equimolar quantities of dineopentylaluminum hydride, which had triple-bond activation and had a five-membered AlPC3 heterocycle in which a C═C bond was bonded to the P and Al atoms of an Al/p FLP.
TL;DR: Two alternate pathways--funded upon the differences in steric and electronic preferences of these two complexes--is proposed for the selectivity of linear versus branched products.
Abstract: The carbonyl-directed C3-H activation and alkylation of 2-aroylbenzo[b]furans with acrylates occurs selectively either in a linear or branched fashion, depending on the catalyst employed; [Ru(p-cymene)Cl2]2 or Ru(PPh3)3Cl2, respectively. Two alternate pathways--funded upon the differences in steric and electronic preferences of these two complexes--is proposed for the selectivity of linear versus branched products.
TL;DR: In this paper, three metal-free catalytic methodologies available for the reduction of carbon-nitrogen double bond are discussed: binaphthol-derived phosphoric acids catalyzed reductions, with dihydropyridine-based compound as the reducing agent; trichlorosilane mediated reductions, in the presence of catalytic amounts of chiral Lewis bases, that involves the use of a combination of a strong Lewis acid with a variety of sterically encumbered Lewis bases.
TL;DR: The results are summarized showing that increasingly synthetically challenging targets such as iminoboryl (B≡N), oxoboryL (B ≡O), and diborene (B═B) fragments can be stabilized in the coordination sphere of late transition metals.
Abstract: Because of their unusual structural and bonding motifs, multiply bonded boron compounds are fundamentally important to chemists, leading to enormous research interest. To access these compounds, researchers have introduced sterically demanding ligands that provide kinetic as well as electronic stability. A conceptually different approach to the synthesis of such compounds involves the use of an electron-rich, coordinatively unsaturated transition metal fragment. To isolate the plethora of borane, boryl, and borylene complexes, chemists have also used the coordination sphere of transition metals to stabilize reactive motifs in these molecules. In this Account, we summarize our results showing that increasingly synthetically challenging targets such as iminoboryl (B≡N), oxoboryl (B≡O), and diborene (B═B) fragments can be stabilized in the coordination sphere of late transition metals. This journey began with the isolation of two new iminoboryl ligands trans-[(Cy3P)2(Br)M(B≡N(SiMe3))] (M = Pd, Pt) attached to palladium and platinum fragments. The synthesis involved oxidative addition of the B-Br bond in (Me3Si)2N═BBr2 to [M(PCy3)2] (M = Pt, Pd) and the subsequent elimination of Me3SiBr at room temperature. Variation of the metal, the metal-bound coligands, and the substituent at the nitrogen atom afforded a series of analogous iminoboryl complexes. Following the same synthetic strategy, we also synthesized the first oxoboryl complex trans-[(Cy3P)2BrPt(BO)]. The labile bromide ligand adjacent to platinum makes the complex a viable candidate for further substitution reactions, which led to a number of new oxoboryl complexes. In addition to allowing us to isolate these fundamental compounds, the synthetic strategy is very convenient and minimizes byproducts. We also discuss the reaction chemistry of these types of compounds. In addition to facilitating the isolation of compounds with B≡E (E = N, O) triple bonds, the platinum fragment can also stabilize a diborene (RB═BR) moiety, a bonding motif that thus far had only been accessible when stabilized by N-heterocyclic carbenes (NHCs). In the new π-diborene [(Et3P)2Pt(B2Dur2)] (Dur = 2,3,5,6-Me4-C6H) complex, the diborene ligand receives electron density from Pt, leading to a strong Pt-B bond and a B═B bond. We attribute this result to the very short B═B bond distance (1.51(2) A) while coordinated to platinum. Overall, an increasing number of chemists are examining the chemistry of multiply bound boron compounds. The isolation of an oxoboryl complex is of special interest not only from a structural standpoint but also because of its orbital similarities to the ubiquitous CO ligand. Detailed computational studies of the π-diborene complex [(Et3P)2Pt(B2Dur2)] show that the bonding properties of this molecule violate the widely accepted Dewar-Chatt-Duncanson (DCD) bonding model.
TL;DR: Investigation of the Diels-Alder reactions of pentacene, 6,13-bis(2-trimethylsilylelethynyl)pentacene (TMS-PT), bistetracene (BT), and 8,17-bis (2- Trimethyl silylethunyl)bistetraceene (tMS-BT) with the [6,6] double bond of [60]fullerene indicates that
Abstract: The Diels–Alder (DA) reactions of pentacene (PT), 6,13-bis(2-trimethylsilylethynyl)pentacene (TMS-PT), bistetracene (BT), and 8,17-bis(2-trimethylsilylethynyl)bistetracene (TMS-BT) with the [6,6] double bond of [60]fullerene have been investigated by density functional theory calculations. Reaction barriers and free energies have been obtained to assess the effects of frameworks and substituent groups on the DA reactivity and product stability. Calculations indicate that TMS-BT is about 5 orders of magnitude less reactive than TMS-PT in the reactions with [60]fullerene. This accounts for the observed much higher stability of TIPS-BT than TIPS-PT when mixed with PCBM. Surprisingly, calculations predict that the bulky silylethynyl substituents of TMS-PT and TMS-BT have only a small influence on reaction barriers. However, the silylethynyl substituents significantly destabilize the corresponding products due to steric repulsions in the adducts. This is confirmed by experimental results here. Architectures of...
TL;DR: DFT calculations at the M06-2X/6-311G(d,p)/PCM(DCM) level confirm that the higher migratory aptitude of Ph versus Me leads to a lower barrier to 1,2- carboboration relative to 1-1-carboboration.
Abstract: The reaction of 8-(trimethylsiloxy)quinoline (QOTMS) with BCl3 and (aryl)BCl2 forms QOBCl2 and QOBCl(aryl). The subsequent addition of stoichiometric AlCl3 follows one of two paths, dependent on the steric demands of the QO ligand and the electrophilicity of the resulting borenium cation. The phenyl- and 5-hexylthienylborenium cations, QOBPh(+) and QOBTh(+), are formed, whereas QOBCl(+) is not. Instead, AlCl3 preferentially binds with QOBCl2 at oxygen, forming QOBCl2 ⋅AlCl3, rather than abstracting chloride. A modest increase in the steric demands around oxygen, by installing a methyl group at the 7-position of the quinolato ligand, switches the reactivity with AlCl3 back to chloride abstraction, allowing formation of Me 2QOBCl(+). All the prepared borenium cations are highly chlorophilic and exhibit significant interaction with AlCl4(-) resulting in an equilibrium concentration of Lewis acidic "AlCl3" species. The presence of "AlCl3(") species limits the alkyne substrates compatible with these borenium systems, with reaction of [QOBPh][AlCl4 ] with 1-pentyne exclusively yielding the cyclotrimerised product, 1,3,5-tripropylbenzene. In contrast, QOBPh(+) and QOBTh(+) systems effect the syn-1,2-carboboration of 3-hexyne. DFT calculations at the M06-2X/6-311G(d,p)/PCM(DCM) level confirm that the higher migratory aptitude of Ph versus Me leads to a lower barrier to 1,2-carboboration relative to 1,1-carboboration.
TL;DR: It is reported that the steric bulk of the substituent can be used to achieve an unusually high selectivity among the C-H bonds that are located at more remote positions of the benzene ring.
Abstract: The benzene ring is one of the most prevalent structural motifs found in organic compounds, and the development of efficient and selective methods for the synthesis of benzene derivatives has attracted the interest of organic chemists for more than a century. When introducing a new substituent onto substituted benzene derivatives, one critical issue is regioselectivity (i.e., which particular C-H bonds will react). One strategy for addressing this issue is to use bulky substituents on the ring—which often are added deliberately—to limit access of a reagent or a catalyst to adjacent C-H bonds, thus directing the reaction to other positions. On page 878 of this issue, Cheng and Hartwig ( 1 ) report that the steric bulk of the substituent can be used to achieve an unusually high selectivity among the C-H bonds that are located at more remote positions of the benzene ring.
TL;DR: An overall mechanism for oxoammonium cation oxidations is suggested, premised on nucleophilic additions to the oxygen atom of the positively charged nitrogen-oxygen double bond.
Abstract: Oxoammonium salt oxidations (using 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate) of alcohols containing a β-oxygen atom in the presence of pyridine yield dimeric esters, while in the presence of 2,6-lutidine the product is a simple aldehyde. The formation of a betaine between pyridine and an aldehyde is presented to explain this disparity in reactivity. The betaine is oxidized by the oxoammonium salt to give an N-acylpyridinium ion that serves as an acylating agent for ester formation. Steric effects deter the formation of such a betaine with 2,6-disubstituted pyridines. A series of alcohols containing a β-oxygen substituent were oxidized to aldehydes in the presence of 2,6-lutidine, and a short study of the relative reactivity of various alcohols is given. An overall mechanism for oxoammonium cation oxidations is suggested, premised on nucleophilic additions to the oxygen atom of the positively charged nitrogen-oxygen double bond. Possible mechanisms for both dimeric oxidations and simple oxidations are given.
TL;DR: It is reported that the hybrid ligand P(iPr)(tBu)2, characterized by a cone angle that is between those of PCy3 and PtBu3, features all of these reactivity properties in a single scaffold.
TL;DR: A series of copper(ii) complexes derived from reduced Schiff base ligands has been synthesized and characterized by single-crystal X-ray diffraction and spectroscopic analyses, and they show significant catalytic activities except for .
Abstract: A series of copper(II) complexes derived from reduced Schiff base ligands has been synthesized and characterized by single-crystal X-ray diffraction and spectroscopic analyses. With the exception of [Cu(Ala5NO2)(H2O)] (1a), which crystallized as a mononuclear repeating unit, [Cu2L2(H2O)x(DMSO)y]·solvent (L = Ala5H (2), Ala5OMe (3a), Ala5Cl (4a), Ala5Br (5a), Gly5Br (6a), Val5Br (7a) and Leu5Br (8a), x = 1 or 2, y = 0 or 1, solvent = MeOH or DMSO and H2O) crystallized as phenoxo-bridged dinuclear building units containing Cu2O2 cores. In 3a, 4a, 5a, 7a and 8a, the axial positions are occupied by solvent ligands and carboxylate oxygen atoms from adjacent dimers, resulting in the formation of 1D helical coordination polymers. In 6a, a 2D network is constructed by utilizing weak Cu⋯O interactions (∼2.7 A) with carboxylate groups. All complexes have been investigated for their catecholase activities with 3,5-DTBC, and they show significant catalytic activities except for 1a. The catalytic activities are also observed to increase with increasing +I effects, as well as increase with increasing steric bulkiness on the α-carbon of the carboxylate group.
TL;DR: The intermolecular radical functionalization of arenes with aryl and alkyl H-phosphinate esters, as well as diphenylphosphine oxide and H- phosphonate diesters, is described.
Abstract: The intermolecular radical functionalization of arenes with aryl and alkyl H-phosphinate esters, as well as diphenylphosphine oxide and H-phosphonate diesters, is described. The novel catalytic Mn(II) /excess Mn(IV) system is a convenient and inexpensive solution to directly convert Csp2 H into CP bonds. The reaction can be employed to functionalize P-stereogenic H-phosphinates since it is stereospecific. With monosubstituted aromatics, the selectivity for para-substitution increases in the order (RO)2 P(O)H
TL;DR: In this paper, a novel energy decomposition analysis (EDA) based on the recently introduced density functional theory (DFT) steric analysis is presented, which has good linear relationships with the total interaction energy for hydrogen-bonding dimers.
Abstract: Application of a novel energy decomposition analysis (EDA) based on the recently introduced density functional theory (DFT) steric analysis is presented. The method is compared with results from the constrained space orbital variations (CSOV) and Bader’s quantum theory of atoms in molecules (QTAIM) topological analysis. These two analyses explain the driving forces for the formation of dimers from different perspectives. The components of the DFT steric analysis are shown to have good linear relationships with the total interaction energy for hydrogen-bonding dimers. It is observed that some components from the new EDA method, such as steric energy, favor the formation of dimers. Moreover, comparison of the different contributions between CSOV and the DFT steric analysis provides additional insights into the physical meaning of the respective components. In addition to the total interaction energy, DFT steric energy has been found to correlate with the electron density at critical points from QTAIM analysis in different patterns for different molecular systems, which qualitatively accounts for the linear relationships between the steric and total interaction energy. The DFT steric energy is found to represent effects arising from the spatial arrangement of the electron density when dimers form, reminiscent of the steric effects invoked in chemical systems.
TL;DR: In the case of the quinolinium and pyridinium salts, the presence of a 3-carboxyamide group increased both reactivity and diastereoselectivity.
Abstract: Boron-ate complexes derived from enantioenriched secondary benzylic boronic esters and aryl lithiums have been reacted with quinolinium, pyridinium and dihydroisoquinolinium salts to give enantioenriched heterocyclic structures with very high diastereocontrol over two contiguous stereogenic centres (87: 1 3–99 : 1 dr; >95 : 5 es). The salts were derived from the corresponding heterocycle and Troc-Cl or dimethylTroc-Cl. In the case of the quinolinium and pyridinium salts, the presence of a 3-carboxyamide group increased both reactivity and diastereoselectivity. The unusually high diastereoselectivity observed is thought to originate from strong cation–π interactions between the cationic heterocycle and the electron rich benzylic boronate complex with minimisation of steric interactions between the substituents on the ate complex and the non-planar substituents on the heterocycle.
TL;DR: In this paper, the rhodium(III)-catalyzed oxidative annulations of aryl ketoximes with diphenylacetylene by the cleavage of three C-H bonds, one C-O bond and the formation of four C C-N bonds simultaneously have been developed.
Abstract: The rhodium(III)-catalyzed oxidative annulations of aryl ketoximes with diphenylacetylene by the cleavage of three C-H bonds, one C-O bond and the formation of four C C bonds, one C N bonds simultaneously have been developed. This protocol is scalable and compatible with various functional groups, providing an expeditious access to highly congested polycyclic aromatic/heteroaromatic hydrocarbons.