Stereoselective [4+2]‐Cycloaddition with Chiral Alkenylboranes

Ni, Dongshun; Witherspoon, Brittany P.; Zhang, Hong; Zhou, Chen; Houk, K. N.; Brown, M. Kevin

doi:10.1002/ange.202000652

Cited by 8 publications

(6 citation statements)

References 84 publications

(42 reference statements)

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“…21,29,33 This is in a good agreement with the fact that the aromaticplanar Bdan group is less bulky than the Bpin group. 13,27,32,42 Therefore, it would appear that the diastereoselectivity in this case is driven primarily by sterics.…”

Section: Resultsmentioning

confidence: 92%

“…We posited that an efficient way to prepare gem-diboryl-norbornene structural motifs 4 would be through a [4+2] cycloaddition reaction of gem-diborylalkenes 2 with cyclopentadiene-CP 3. Although the [4+2] cycloaddition reactions of vinylboranates, 26 e.g., 1, are well documented in the literature (Figure 2A), [27][28][29][30] to the best of our knowledge, the use of gem-diboryllkenes (2) in these types of reactions is rare, despite the potential to provide new and efficient strategies to efficiently construct complex molecules (Figure 2B). 28,30 Recently, we reported a photoredox-mediated reaction of gemdiborylalkenes 31 and showed that gemdiboryalkenes (2) are more electron deficient compared to vinyl-boron 1; 31 hence, 2 should serve as a suitable dienophile for this type of cycloaddition reaction.…”

Section: Resultsmentioning

confidence: 99%

“…We utilized gem-diborylnorbornene in the synthesis, for the first time, of gem-diboryl-based polymers through ROMP. Studies to achieve an enantioselective DA transformation using chiral gemdiborylalkenes 27 as well as new post-polymerization transformations of gem-diborylcycloalkenebased polymers are currently under investigation and will be reported in due course.…”

Section: Discussionmentioning

confidence: 99%

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

Eghbarieh¹,

Hanania²,

Zamir³

et al. 2021

Preprint

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Although gem-diborylalkenes are known to be among the most valuable reagents in modern organic synthesis, providing a rapid access to a wide array of transformations, including the construction of C−C and C‐heteroatom bonds, their use as dienophile-reactive groups has been rare. Herein we report the Diels-Alder (DA) reaction of (unsymmetrical) gem-diborylalkenes. These reactions provide a general and efficient method for the stereoselective conversion of gem-diborylalkenes to rapidly access 1,1-bisborylcyclohexenes. Using the same DA reaction manifold with borylated-dienes and gem-diborylalkenes, we also developed a concise, highly regioselective synthesis of 1,1,2-tris- and 1,1,3,4-tetrakis(boronates)cyclohexenes, a family of compounds that currently lack efficient synthetic access. Furthermore, DFT calculations provided insight into the underlying factors that control the chemo-, regio, and stereoselectivity of these DA reactions. This method also provides stereodivergent syntheses of gem-diboryl-norbornenes. The utility of the gem-diboryl-norbornene building blocks was demonstrated by ring-opening metathesis polymerization (ROMP), providing a highly modular approach to the first synthesis of the gem-diboron-based polymers. Given its simplicity and versatility, we believe that this novel DA and ROMP approach holds great promise for organoboron synthesis as well as organoboron-based polymers and that it will result in more novel transformations in both academic and industrial research.<br>

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Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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

Eghbarieh¹,

Hanania²,

Zamir³

et al. 2021

Preprint

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“…The author engages Corey's activated chiral oxazaborolidine based chiral auxilary [15] to maintain the rigid structure. They developed a stereoselective [4+2]‐cycloaddition protocol accomplishing N ‐protonated alkenyl oxazaborolidines as a dienophile [46] . They cleverly designed the 5 : 5 fused ring system, where the substituent on the concave face energetically disfavors the approach of diene.…”

Section: Asymmetric [4+2] Cycloaddition Using Organoboron Compoundmentioning

confidence: 99%

“…They developed a stereoselective [4 + 2]-cycloaddition protocol accomplishing Nprotonated alkenyl oxazaborolidines as a dienophile. [46] They cleverly designed the 5 : 5 fused ring system, where the substituent on the concave face energetically disfavors the approach of diene. The author utilized diphenylprolinol as the chiral auxiliary, which also generated a chiral alkenyl oxazabor- olidine in situ and later on converted into a highly reactive dienophile via Lewis acid or Brønsted acid activation.…”

Section: Asymmetric Diels-alder Reaction Using Chiral Auxiliarymentioning

confidence: 99%

Organoboron Compounds Towards Asymmetric Pericyclic Reaction; Exploitation to Bioactive Molecule Synthesis

et al. 2022

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Organic frameworks containing boron as one of the units have wide application in organic synthesis. Due to the non‐toxicity and cheap accessibility, the organoboron compounds have gained increased demand towards the organic chemist. Besides, there has been a huge progress in the area of chiral organoboron synthesis, which allows direct access to chiral synthons. Among other methods developed for the asymmetric synthesis of organoboron compounds, pericyclic reaction plays an important role. Cycloaddition reactions using vinyl boronic esters have been extensively reported for the synthesis of cyclic boronic esters. Asymmetric cycloaddition using organoboron compound opens a quick access to various intermediates with multiple chiral centers, which has been utilized for the total synthesis of bioactive molecules. This mini‐review outlines various asymmetric pericyclic reactions developed to date demonstrating its applicability towards bioactive molecule synthesis.

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Regioselectivity Switch Towards the Development of Innovative Diels‐Alder Cycloaddition and Productive Applications in Organic Synthesis

2022

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The Diels‐Alder (DA) reaction is one of the fascinating synthetic strategies known for its pericyclic action and concerted mechanism that leads to various targets. Numerous synthetic pursuits have been rewarded with conceptually distinct and efficient ways. To date, extensive and spectacular accomplishments have been made in the field of Diels‐Alder chemistry to overcome the complexities of organic synthesis that inspired organic chemists to focus on expanding and establishing the postulates. In principle, DA reactions are governed by their straightforward reactivity pattern with a high degree of certainty, primarily attributed to the HOMO‐LUMO separation of reacting partners. Furthermore, general forecasts rely on account of background studies, conveniently hypothesizing the stereochemical outcomes and reaction dynamic pathways. DA has recently emerged as a technique for establishing a variety of products from the same reacting species under varying reaction conditions rather than a general reactivity profile. Such exceptional results are of significant interest in organic synthesis to pursue the challenges of unanticipated product establishment. Herein, we summarize the impressive finding of the remarkable switch in the regioselectivity and diastereoselectivity of DA reactions under a diverse set of reaction protocols in light of Diels‐Alder's unending importance in chemical science. This review aims to establish a beneficial account of Diels‐Alder towards the astonishing switches extended to study varying synthetic versions in organic synthesis protocols attributed to natural and biologically active scaffolds. This review also provides insight into distinct reaction dynamics in DA reactions that are subjected to access molecular frameworks ranging from simple to complicated ones to foster high levels of innovation in chemical sciences.

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Stereoselective [4+2]‐Cycloaddition with Chiral Alkenylboranes

Cited by 8 publications

References 84 publications

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

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

Organoboron Compounds Towards Asymmetric Pericyclic Reaction; Exploitation to Bioactive Molecule Synthesis

Regioselectivity Switch Towards the Development of Innovative Diels‐Alder Cycloaddition and Productive Applications in Organic Synthesis

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