Allylboronic Acid Pinacol Ester Research Articles

19F magnetic resonance probes for detecting formaldehyde

Herein we report two separate 19F magnetic resonance (MR) probes responsive towards formaldehyde. Both agents were synthesized in a single step via aminoallylation of either 4-fluorobenzaldehyde (1FA) or 4-(trifluoromethyl)benzaldehyde (3FA) with ammonia and allylboronic acid pinacol ester. Condensation of the resulting homoallylic amines 1FA and 3FA with formaldehyde, followed by a 2-aza-Cope rearrangement and subsequent hydrolysis affords 4-fluorobenzaldehyde and 4-(trifluoromethyl)benzaldehyde, respectively. In the case of 1FA, this transformation is evidenced by a concomitant downfield shift in the 19F MR signal from −115 ppm to −103 ppm. Further, this transformation is selective towards formaldehyde over other reactive carbonyl species. While 3FA exhibits similar selectivity towards formaldehyde, this more sensitive probe is limited by the small chemical shift difference (0.7 ppm) following its activation.

Flame-retardant single-ion conducting polymer electrolytes based on anion acceptors for high-safety lithium metal batteries

A flame-retardant single-ion conducting polymer electrolyte was constructed by incorporating allylboronic acid pinacol ester into the 3D network to trap the anions, leading to unity lithium-ion transference number and high ionic conductivity.

Syntheses of Molybdenum and Tungsten Imido Alkylidene Complexes that Contain a Bidentate Oxo/Thiolato Ligand

Abstract3,3′,5,5′‐Tetra‐tert‐butyl‐2′‐sulfanyl[1,1′‐biphenyl]‐2‐ol (H2[tBu4OS]) was prepared in 24 % yield overall from the analogous biphenol using standard techniques. Addition of H2[tBu4OS] to Mo(NAr)(CHCMe2Ph)(2,5‐dimethylpyrrolide)2 led to formation of Mo(NAr)(CHCMe2Ph)[tBu4OS], which was trapped with PMe3 to give Mo(NAr)(CHCMe2Ph)[tBu4OS](PMe3) (1(PMe3)). An X‐ray crystallographic study of 1(PMe3) revealed that two structurally distinct square pyramidal molecules are present in which the alkylidene ligand occupies the apical position in each. Both 1(PMe3)A and 1(PMe3)B are disordered. Mo(NAd)(CHCMe2Ph)(tBu4OS)(PMe3) (2(PMe3); Ad=1‐adamantyl) and W(NAr)(CHCMe2Ph)(tBu4OS)(PMe3) (3(PMe3)) were prepared using analogous approaches. 1(PMe3) reacts with ethylene (1 atm) in benzene within 45 minutes to give an ethylene complex Mo(NAr)(tBu4OS)(C2H4) (4) that is isolable and relatively stable toward loss of ethylene below 60 °C. An X‐ray study shows that the bond distances and angles for the ethylene ligand in 4 are like those found for bisalkoxide ethylene complexes of the same general type. Complex 1(PMe3) in the presence of one equivalent of B(C6F5)3 catalyzes the homocoupling of 1‐decene, allyltrimethylsilane, and allylboronic acid pinacol ester at ambient temperature. 1(PMe3), 2(PMe3), and 3(PMe3) all catalyze the ROMP of rac‐endo,exo‐5,6‐dicarbomethoxynorbornene (rac‐DCMNBE) in the presence of B(C6F5)3, but the polyDCMNBE that is formed has a random structure.

Improving long-term cyclic performance of LiNi0.8Co0.15Al0.05O2 cathode by introducing a film forming additive

Layered structure Ni-rich LiNi0.8Co0.15Al0.05O2 cathode has been considered as a higher energy density candidate, but the problems of poor interface stability and cyclic performance restrain its further application. Herein, a functional vinyl (CC) group allylboronic acid pinacol ester (ABAPE) is introduced as a film forming additive. Linear sweep voltammetry test shows ABAPE could be oxidized prior to blank electrolyte on the cathode and prevent the electrolyte decomposition. The LiNi0.8Co0.15Al0.05O2/graphite pouch cells which contained 1.5% ABAPE shows remarkable cyclic performance of 87.7% capacity retention compared with 71.8% of blank electrolyte after 500cycles. This is attributed to the protective surface layer which prevents the further decomposition of electrolyte and transition metal ion dissolution, thus stabilizing the electrode-electrolyte interface. Scanning electron microscopy and X-ray photoelectron spectroscopy results also demonstrate that there are less unwanted lithium compounds on the additive-contained cathode.

Practical, Broadly Applicable, α-Selective, Z-Selective, Diastereoselective, and Enantioselective Addition of Allylboron Compounds to Mono-, Di-, Tri-, and Polyfluoroalkyl Ketones.

A practical method for enantioselective synthesis of fluoroalkyl-substituted Z-homoallylic tertiary alcohols has been developed. Reactions may be performed with ketones containing a polylfluoro-, trifluoro-, difluoro-, and monofluoroalkyl group along with an aryl, a heteroaryl, an alkenyl, an alkynyl, or an alkyl substituent. Readily accessible unsaturated organoboron compounds serve as reagents. Transformations were performed with 0.5-2.5 mol % of a boron-based catalyst, generated in situ from a readily accessible valine-derived aminophenol and a Z- or an E-γ-substituted boronic acid pinacol ester. With a Z organoboron reagent, additions to trifluoromethyl and polyfluoroalkyl ketones proceeded in 80-98% yield, 97:3 to >98:2 α:γ selectivity, >95:5 Z:E selectivity, and 81:19 to >99:1 enantiomeric ratio. In notable contrast to reactions with unsubstituted allylboronic acid pinacol ester, additions to ketones with a mono- or a difluoromethyl group were highly enantioselective as well. Transformations were similarly efficient and α- and Z-selective when an E-allylboronate compound was used, but enantioselectivities were lower. In certain cases, the opposite enantiomer was favored (up to 4:96 er). With a racemic allylboronate reagent that contains an allylic stereogenic center, additions were exceptionally α-selective, affording products expected from γ-addition of a crotylboron compound, in up to 97% yield, 88:12 diastereomeric ratio, and 94:6 enantiomeric ratio. Utility is highlighted by gram-scale preparation of representative products through transformations that were performed without exclusion of air or moisture and through applications in stereoselective olefin metathesis where Z-alkene substrates are required. Mechanistic investigations aided by computational (DFT) studies and offer insight into different selectivity profiles.

Enantioselective Allyl-, and Allenylboration of Aldehydes Catalyzed by Chiral Hydroxyl Carboxylic Acid

Asymmetric allylboration of aldehydes with allylboronic acid pinacol ester catalyzed by chiral hydroxyl carboxylic acid is described. This reaction provides synthetically useful homoallyl alcohols in high yield with good to high enantioselectivity. The present catalytic protocol was also examined in asymmetric allenylboration of aldehydes at elevated temperature to afford chiral homopropargyl alcohols with reasonable asymmetric induction.

Bismuth-catalyzed allylation of para-quinone methides.

An efficient 1,6-allylation addition of para-quinone methides to allylboronic acid pinacol ester catalyzed by bismuth(iii) triflate was developed. The reaction proceeded smoothly in high yields under mild conditions with only 0.5-5 mol% catalyst.

Evaluation of Allylboronic Acid Pinacol Ester as Effective Shutdown Overcharge Additive for Lithium Ion Cells

Allylboronic acid pinacol ester (ABPE) was investigated as shutdown overcharge additive to increase the intrinsic safety of lithium ion cells during operation at elevated charge cutoff potentials up to 4.5 V vs. Li/Li+. It was demonstrated that the additive had no negative influence on the cycling performance of LiNi1/3Co1/3Mn1/3O2 (NMC-111)/graphite full cells operated in a standard operation voltage range between 2.5 V and 4.2 V. Electrochemical impedance spectroscopy was used to study the influence of the electrolyte additive on the impedance before and after overcharge and concomitant cell shutdown. Thereby, an immense increase in the charge transfer resistance after electrode shutdown was observed, thus, hinting to the formation of a lithium ion-insulating layer on the positive electrode surface. To further elucidate the working principle of the shutdown additive, surface investigations by means of scanning electron microscopy and X-ray photoelectron spectroscopy were carried out. The existence of a surface layer consisting mainly of polymeric species was proven. The presented results open up a new family of compounds for overcharge protection.

ChemInform Abstract: Diastereoselective Amidoallylation of Glyoxylic Acid with Chiral tert‐Butanesulfinamide and Allylboronic Acid Pinacol Esters: Efficient Synthesis of Optically Active γ,δ‐Unsaturated α‐Amino Acids.

Abstract A convenient synthesis of δ,γ-unsaturated amino acids has been developed. After a mixture of ( R )- tert -butanesulfinamide and glyoxylic acid with molecular sieves in CH 2 Cl 2 was stirred for 42 h at room temperature, allylboronic acid pinacol ester was added to the mixture to give ( R )-2-(( R )- tert -butanesulfinamido)pent-4-enoic acid with high diastereoselectivity. The corresponding reaction of ( Z )-crotylboronic acid pinacol ester produced no product; however, that of ( E )-crotylboronic acid pinacol ester produced (2 R, 3 S )-2-(( R )- tert- butylsulfinamido)-3-methylpent-4-enoic acid with excellent diastereoselectivity.

Diastereoselective amidoallylation of glyoxylic acid with chiral tert-butanesulfinamide and allylboronic acid pinacol esters: efficient synthesis of optically active γ,δ-unsaturated α-amino acids

A convenient synthesis of δ,γ-unsaturated amino acids has been developed. After a mixture of (R)-tert-butanesulfinamide and glyoxylic acid with molecular sieves in CH2Cl2 was stirred for 42h at room temperature, allylboronic acid pinacol ester was added to the mixture to give (R)-2-((R)-tert-butanesulfinamido)pent-4-enoic acid with high diastereoselectivity. The corresponding reaction of (Z)-crotylboronic acid pinacol ester produced no product; however, that of (E)-crotylboronic acid pinacol ester produced (2R,3S)-2-((R)-tert-butylsulfinamido)-3-methylpent-4-enoic acid with excellent diastereoselectivity.

Regioselective Cross-Coupling of Allylboronic Acid Pinacol Ester Derivatives with Aryl Halides via Pd-PEPPSI-IPent

The cross-coupling reactions of allylboronic acid pinacol ester derivatives with aryl and heteroaryl halides occurred with high selectivity (>97%) at the α-carbon of the allylboron reagent in the presence of Pd-PEPPSI-IPent precatalyst and 5 M KOH in refluxing THF. In the case of trisubstituted allylboronates with different substituents on the olefin, minor olefin geometry isomerization was observed (E/Z ≈ 80/20).

Diversity-Oriented Approach to Macrocyclic Cyclophane Derivatives by Suzuki–Miyaura Cross-Coupling and Olefin Metathesis as Key Steps

Palladium-catalyzed Suzuki-Miyaura (SM) cross-coupling reaction with allylboronic acid pinacol ester and titanium assisted cross-metathesis (CM)/ring-closing metathesis (RCM) cascade has been used to synthesize macrocyclic cyclophane derivatives.

Homoallylic Alcohols via a Chemo‐Enzymatic One‐Pot Oxidation–Allylation Cascade

AbstractA chemo‐enzymatic one‐pot, two‐step transformation of (hetero)‐benzylic and cinnamic alcohols to yield the elongated homoallylic sec‐alcohols in water in up to 96% isolated yield has been developed. The sequence comprised an enzymatic alcohol oxidation using galactose oxidase from Fusarium sp. NRRL 2903 to furnish the corresponding aldehydes, which were subjected directly to allylation via indium(0)‐mediated Barbier‐type coupling with allyl bromide or by addition of allylboronic acid pinacol ester.

Catalytic enantioselective allylation of dienals through the intermediacy of unsaturated pi-allyl complexes.

The nickel-catalyzed enantioselective addition of allylboronic acid pinacol ester [allylB(pin)] to alpha,beta,gamma,delta-unsaturated aldehydes is described. This reaction results in a remarkable inversion of substrate olefin geometry, providing the Z,E-configured reaction product in good enantioselectivity and olefin stereoselectivity. The reaction appears to proceed by conversion of the dienal to an unsaturated pi-allyl complex followed by reductive elimination via transition state II. Enantioselectivities range from 73-94% ee for a range of delta-substituted dienals when chiral ligand L3 is employed.

Catalytic Enantioselective Allyl- and Crotylboration of Aldehydes Using Chiral Diol•SnCl4 Complexes. Optimization, Substrate Scope and Mechanistic Investigations

We report a novel class of C2-symmetric chiral diols derived from the hydrobenzoin skeleton. The combination of these diols with SnCl4 under Yamamoto's concept of Lewis acid assisted Brønsted acidity (LBA catalysis) leads to high levels of asymmetric induction in the allylboration of aldehydes by commercially available allylboronic acid pinacol ester 1a. The corresponding homoallylic alcohol products of synthetically useful aliphatic aldehydes are obtained in excellent yields with up to 98:2 er. This combined acid manifold is also efficient in catalyzing the diastereo- and enantioselective crotylboration of aldehydes, thus providing the propionate units in >95:5 dr and up to 98:2 er. The X-ray crystal structure of the optimal diol x SnCl4 complex, Vivol (4m) x SnCl4, unambiguously shows the Brønsted acidic character of this LBA catalyst and its highly dissymmetrical environment. Further controls have ruled out a possible boron trans-esterification mechanism with the chiral diol and point to LBA catalyst-derived activation of the pinacol allylic boronates 1. Due to slow dissociation of the diol x SnCl4 complex, a small excess of diol is required in order to suppress a competing racemic cycle catalyzed by free SnCl4.

Asymmetric Ni-Catalyzed Conjugate Allylation of Activated Enones

The nickel-catalyzed enantioselective addition of allylboronic acid pinacol ester, allylB(pin), is described. This reaction is highly effective with dialkylidene ketones and favors the allylation of the benzylidene site in nonsymmetric substrates. The reaction appears to proceed by conversion of the dialkylidene ketone substrate to an unsaturated pi-allyl complex (I), followed by reductive elimination. Enantioselectivities range from 91 to 94% ee for a range of substrates when chiral ligand 14 is employed.

Conversion of Ni(II)-Allylporphyrins to α,β-Unsaturated Formylporphyrins via a Nickel-Promoted Reaction

A new route to alpha,beta-unsaturated formylporphyrins begins with the synthesis of allyl-substituted porphyrins via the Suzuki cross-coupling reaction of bromoporphyrins and allylboronic acid pinacol ester in 50-95% yield. Treatment of allyl-substituted porphyrins with nickel acetate in N,N-dimethylformamide (DMF) then affords mono- and diacroleinylporphyrins in up to 70% yield.

Catalytic Enantioselective Allylation of Ketoimines

A general catalytic allylation of simple ketoimines was developed using 1 mol % of CuF.3PPh(3) as catalyst, 1.5 mol % of La(O(i)Pr)(3) as the cocatalyst, and stable and nontoxic allylboronic acid pinacol ester as the nucleophile. This reaction constituted a good template for developing the first catalytic enantioselective allylation of ketoimines. In this case, using LiO(i)Pr as the cocatalyst produced higher enantioselectivity and reactivity than La(O(i)Pr)(3). Thus, using the CuF-cyclopentyl-DuPHOS complex (10 mol %) and LiO(i)Pr (30 mol %) in the presence of (t)BuOH (1 equiv) produced high enantioselectivity up to 93% ee from a range of aromatic ketoimines. Mechanistic studies indicated that LiO(i)Pr accelerates the reaction by increasing the concentration of an active nucleophile, allylcopper.