Stereoselective Diels–Alder Reactions of <i>gem</i>-Diborylalkenes: Toward the Synthesis of <i>gem-</i>Diboron-Based Polymers

Eghbarieh, Nadim; Hanania, Nicole; Zamir, Alon; Nassir, Molhm; Stein, Tamar; Masarwa, Ahmad

doi:10.1021/jacs.1c01471

Cited by 34 publications

(42 citation statements)

References 60 publications

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“…For example, they participate in [4 + 2], [3 + 2], and [2 + 2] cycloadditions, under both thermal and photochemical conditions. In addition, the Diels–Alder (DA) reactions of unsaturated boron compounds have been explored for many decades. , Early reports described the reactions of vinyl- and ethynylboronic esters, which were later extended to a wide variety of boron-substituted dienophiles and dienes. However, although allenylboron compounds have been used in many organic reactions, , including propargylations and allenylations and Suzuki cross-couplings and related reactions, curiously, the potential in cycloaddition reactions has not been disclosed.…”

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confidence: 99%

Allenylboronic Acid Pinacol Ester: A Selective Partner for [4 + 2] Cycloadditions

et al. 2021

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We have studied the reaction of allenylboronic acid pinacol ester with cyclopentadiene with experimental and computational methods. The reaction occurred efficiently with complete Diels–Alder periselectivity and regioselectivity at the proximal double bond. The concerted mechanism for the observed transformation was computed to be favored over competitive addition to the distal double bond, [3,3]-sigmatropic rearrangements, and stepwise radical mechanism. This unprecedented Diels–Alder reaction enables the construction of synthetically versatile boron-substituted cycloadducts.

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confidence: 99%

Allenylboronic Acid Pinacol Ester: A Selective Partner for [4 + 2] Cycloadditions

et al. 2021

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“…To study the vulcanization process of styrene-butadiene rubber (SBR) activated by ZDMC, this work used the DFT method to calculate all stationary points along reaction pathways at the ωB97X-D/BSII//ωB97X-D/BSI level using the Gaussian09 program. − BSI denotes the LANL2DZ basis set for Zn and 6-31G(d) basis set for other atoms, and BSII denotes the LANL2DZ basis set for Zn and 6-31++G(d,p) basis set for other atoms. − Unless otherwise specified, all energies discussed in the following sections are Gibbs free energies calculated at 298.15 K. All stationary points have been confirmed by frequency analysis, and all transition states have been verified with one and only one imaginary frequency. The MCV method was used to choose 3-ethyl-pentene as the simplified model of the SBR single-chain (see Figure S1 of Supporting Information).…”

Section: Computational Detailsmentioning

confidence: 99%

Mechanism of the Zinc Dithiocarbamate-Activated Rubber Vulcanization Process: A Density Functional Theory Study

Shi

Yinna

et al. 2021

ACS Appl. Polym. Mater.

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To elucidate the mechanism of sulfur vulcanization of butadiene-styrene rubber by zinc dithiocarbamate (ZDMC), the density functional theory method was used to investigate the nature of the vulcanization induction and vulcanization periods of the rubber vulcanization process mediated by ZDMC. A mechanism for the sulfur pyrolysis by bimolecular ZDMC during the vulcanization induction period is proposed in which sulfur is inserted to produce active sulfurating agents. The calculated results indicate that the cross-link precursors of perthiols are generated in the reaction of active vulcanizing agents and single chains of rubber molecules and that ZDMC could promote the cross-linking of cross-link precursors during vulcanization to form the vulcanizate. This work established the mechanism of Zn(II)-activated sulfur vulcanization, which provided theoretical insights into the development of the rubber vulcanization accelerators.

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“…Despite these milestone achievements, most reports have mainly focused on the development of a single-step reaction by employing mono-organoboron compounds (Figure a). While these step-by-step sequences are well-tailored for target-oriented synthesis, recent advances have shown that modular and chemoselective transformations of poly(organoborons), consisting of two or more boron groups on the same molecule, can be an efficient strategy for the rapid and diverse synthesis of molecules with higher complexity (Figure b) . Pioneering works by Burke and Suginome demonstrated that the boron-masking/unmasking strategy enables consecutive C–C bond formation reactions of poly(organoborons) via palladium-catalyzed Suzuki–Miyaura cross-coupling (SMC), although this approach is only applicable to poly(organoborons) bearing boron groups at sp 2 -hybridized carbon centers.…”

Section: Introductionmentioning

confidence: 99%

Catalytic Chemo- and Enantioselective Transformations of gem-Diborylalkanes and (Diborylmethyl)metallic Species

2021

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Metrics & MoreArticle Recommendations CONSPECTUS: Chemo-and stereoselective transformations of polyborylalkanes are powerful and efficient methods to access optically active molecules with greater complexity and diversity through programmed synthetic design. Among the various polyborylalkanes, gem-diborylalkanes have attracted much attention in organic chemistry as versatile synthetic handles. The notable advantage of gem-diborylalkanes lies in their ability to generate two key intermediates, α-borylalkyl anions and (gem-diborylalkyl) anions. These two different intermediates can be applied to various enantioselective reactions to rapidly access a diverse set of enantioenriched organoboron compounds, which can be further manipulated to generate various chiral molecule libraries via stereospecific C(sp 3 )−B bond transformations.In this Account, we summarize our recent contributions to the development of catalytic chemo-and stereoselective reactions using gem-diborylalkanes as versatile nucleophiles, which can be categorized as follows:(1) copper-catalyzed enantioselective coupling of gem-diborylalkanes with electrophiles and (2) the design and synthesis of (diborylmethyl)metallic species and their applications to enantioselective reactions. Since Shibata and Endo reported the Pdcatalyzed chemoselective Suzuki−Miyaura cross-coupling of gem-diborylalkanes with organohalides in 2014, Morken and Hall subsequently developed the first enantioselective analogous reactions using TADDOL-derived chiral phosphoramidite as the supporting ligand of a palladium catalyst. This discovery sparked interest in the catalytic enantioselective coupling of gemdiborylalkanes with electrophiles. Our initial studies focused on generating chiral (α-borylmethyl)copper species by enantiotopicgroup-selective transmetalation of gem-diborylalkanes with chiral copper complexes and their reactions with various aldimines and ketimines to afford syn-β-aminoboronate esters with excellent enantio-and diastereoselectivity. Moreover, we developed the enantioselective allylation of gem-diborylalkanes that proceeded by reaction of in situ-generated chiral (α-borylalkyl)copper and allyl bromides. Mechanistic investigations revealed that the enantiotopic-group-selective transmetalation between gem-diborylalkanes and the chiral copper complex occurred through the open transition state rather than the closed transition state, thereby effectively generating chiral (α-borylmethyl)copper species. We also utilized (diborylmethyl)metallic species such as (diborylmethyl)silanes and (diborylmethyl)zinc halides in catalytic enantioselective reactions. We succeeded in developing the enantiotopic-group-selective cross-coupling of (diborylmethyl)silanes with aryl iodides to afford enantioenriched benzylic 1,1-silylboronate esters, which could be used for further consecutive stereospecific transformations to afford various enantioenriched molecules. In addition, we synthesized (diborylmethyl)zinc halides for the first time by the transmetalation of isolated (diborylmeth...

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Stereoselective Diels–Alder Reactions of gem-Diborylalkenes: Toward the Synthesis of gem-Diboron-Based Polymers

Cited by 34 publications

References 60 publications

Allenylboronic Acid Pinacol Ester: A Selective Partner for [4 + 2] Cycloadditions

Allenylboronic Acid Pinacol Ester: A Selective Partner for [4 + 2] Cycloadditions

Mechanism of the Zinc Dithiocarbamate-Activated Rubber Vulcanization Process: A Density Functional Theory Study

Catalytic Chemo- and Enantioselective Transformations of gem-Diborylalkanes and (Diborylmethyl)metallic Species

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