Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2019 Sep 11;141(36):14104-14109.
doi: 10.1021/jacs.9b07564. Epub 2019 Sep 3.

1,2-Boron Shifts of β-Boryl Radicals Generated from Bis-boronic Esters Using Photoredox Catalysis

Daniel Kaiser  1 , Adam Noble  1 , Valerio Fasano  1 , Varinder K Aggarwal  1
Affiliations

1,2-Boron Shifts of β-Boryl Radicals Generated from Bis-boronic Esters Using Photoredox Catalysis

Daniel Kaiser et al. J Am Chem Soc. .

Abstract

1,2-Bis-boronic esters are versatile intermediates that enable the rapid elaboration of simple alkene precursors. Previous reports on their selective mono-functionalization have targeted the most accessible position, retaining the more hindered secondary boronic ester. In contrast, we have found that photoredox-catalyzed mono-deboronation generates primary β-boryl radicals that undergo rapid 1,2-boron shift to form thermodynamically favored secondary radicals, allowing for selective transformation of the more hindered boronic ester. The pivotal 1,2-boron shift, which has been demonstrated to be stereoretentive, enables access to a wide range of functionalized boronic esters and has been applied to highly diastereoselective fragmentation and transannular cyclization reactions. Furthermore, its generality has been shown in a radical cascade reaction with an allylboronic ester.

PubMed Disclaimer

Conflict of interest statement

Notes

The authors declare no competing financial interests.

Figures

None
Graphical abstract
Scheme 1
Scheme 1. Alkylborons as radical precursors and functionalizations of 1,2-bis-boronic esters.
Scheme 2
Scheme 2. Reaction Scope.a
a Reactions were run on 0.2 mmol scale, unless otherwise noted. Yields are of isolated products. b Isolated as the corresponding alcohols after oxidation. c Using aryllithium D. d Using 2.0 equiv B. e Run on 0.15 mmol scale. f Without tBuOH.
Scheme 3
Scheme 3. Mechanistic Proposal.
Scheme 4
Scheme 4. Additional Studies.
a Isolated as the corresponding alcohols after oxidation.
Scheme 5
Scheme 5. Investigations into the 1,2-Boron Shift.
a Isolated as the corresponding alcohols after oxidation. b Determined by 1H NMR analysis.
See this image and copyright information in PMC

References

    1. Shaw MH, Twilton J, MacMillan DWC. Photoredox Catalysis in Organic Chemistry. J Org Chem. 2016;81:6898. - PMC - PubMed
    2. Narayanama JMR, Stephenson CRJ. Visible Light Photoredox Catalysis: Applications in Organic Synthesis. Chem Soc Rev. 2011;40:102. - PubMed
    3. Prier CK, Rankic DA, MacMillan DWC. Visible Light Photoredox Catalysis with Transition Metal Complexes: Applications in Organic Synthesis. Chem Rev. 2013;113:5322. - PMC - PubMed
    4. Goddard J-P, Ollivier C, Fensterbank L. Photoredox Catalysis for the Generation of Carbon Centered Radicals. Acc Chem Res. 2016;49:1924. - PubMed
    5. Staveness D, Bosque I, Stephenson CRJ. Free Radical Chemistry Enabled by Visible Light-Induced Electron Transfer. Acc Chem Res. 2016;49:2295. - PMC - PubMed
    6. Marzo L, Pagire SK, Reiser O, König B. Visible-Light Photocatalysis: Does It Make a Difference in Organic Synthesis? Angew Chem Int Ed. 2018;57:10034. - PubMed
    1. Yasu Y, Koike T, Akita M. Visible Light-Induced Selective Generation of Radicals from Organoborates by Photoredox Catalysis. Adv Synth Catal. 2012;354:3414.
    2. Lima F, Sharma UK, Grunenberg L, Saha D, Johannsen S, Sedelmeier J, Van der Eycken EV, Ley SV. A Lewis Base Catalysis Approach for the Photoredox Activation of Boronic Acids and Esters. Angew Chem Int Ed. 2017;56:15136. - PMC - PubMed
    3. Lima F, Grunenberg L, Rahman HBA, Labes R, Sedelmeier J, Ley SV. Organic Photocatalysis for the Radical Couplings of Boronic Acid Derivatives in Batch and Flow. Chem Commun. 2018;54:5606. - PubMed
    4. Shu C, Noble A, Aggarwal VK. Photoredox-Catalyzed Cyclobutane Synthesis by a Deboronative Radical Addition-Polar Cyclization Cascade. Angew Chem Int Ed. 2019;58:3870. - PMC - PubMed
    5. Lima F, Kabeshov MA, Tran DN, Battilocchio C, Sedelmeier J, Sedelmeier G, Schenkel B, Ley SV. Visible Light Activation of Boronic Esters Enables Efficient Photoredox C(sp2)-C(sp3) Cross-Couplings in Flow. Angew Chem Int Ed. 2016;55:14085. - PMC - PubMed
    6. Clausen F, Kischkewitz M, Bergander K, Studer A. Catalytic Protodeboronation of Pinacol Boronic Esters: Formal Anti-Markovnikov Hydromethylation of Alkenes. Chem Sci. 2019;10:6210. - PMC - PubMed
    7. Duret G, Quinlan R, Bisseret P, Blanchard N. Boron Chemistry in a New Light. Chem Sci. 2015;6:5366. - PMC - PubMed
    1. Miyazawa K, Yasu Y, Koike T, Akita M. Visible-Light-Induced Hydroalkoxymethylation of Electron-Deficient Alkenes by Photoredox Catalysis. Chem Commun. 2013;49:7249. - PubMed
    2. Miyazawa K, Koike T, Akita M. Hydroaminomethylation of Olefins with Aminomethyltrifluoroborate by Photoredox Catalysis. Adv Synth Catal. 2014;356:2749.
    3. Chinzei T, Miyazawa K, Yasu Y, Koike T, Akita M. Redox-Economical Radical Generation from Organoborates and Carboxylic Acids by Organic Photoredox Catalysis. RSC Adv. 2015;5:21297.
    4. Huo H, Harms K, Meggers E. Catalytic, Enantioselective Addition of Alkyl Radicals to Alkenes via Visible-Light-Activated Photoredox Catalysis with a Chiral Rhodium Complex. J Am Chem Soc. 2016;138:6936. - PubMed
    5. Tellis JC, Primer DN, Molander GA. Single-Electron Transmetalation in Or-ganoboron Cross-Coupling by Photoredox/Nickel Dual Catalysis. Science. 2014;345:433. - PMC - PubMed
    6. Primer DN, Karakaya I, Tellis JC, Molander GA. Single-Electron Transmetalation: An Enabling Technology for Secondary Alkylboron Cross-Coupling. J Am Chem Soc. 2015;137:2195. - PMC - PubMed
    7. Primer DN, Molander GA. Enabling the Cross-Coupling of Tertiary Organoboron Nucleophiles through Radical-Mediated Alkyl Transfer. J Am Chem Soc. 2017;139:9847. - PMC - PubMed
    8. Amani J, Molander GA. Synergistic Photoredox/Nickel Coupling of Acyl Chlorides with Secondary Alkyltrifluoroborates: Dialkyl Ketone Synthesis. J Org Chem. 2017;82:1856. - PMC - PubMed
    9. Huang H, Zhang G, Gong L, Zhang S, Chen Y. Visible-Light-Induced Chemoselective Deboronative Alkynylation under Biomolecule-Compatible Conditions. J Am Chem Soc. 2014;136:2280. - PubMed
    10. Huang H, Jia K, Chen Y. Hypervalent Iodine Reagents Enable Chemoselective Deboronative/Decarboxylative Alkenylation by Photoredox Catalysis. Angew Chem Int Ed. 2015;54:1881. - PubMed
    11. Heitz DR, Rizwan K, Molander GA. Visible-Light-Mediated Alkenylation, Allylation, and Cyanation of Potassium Alkyltrifluoroborates with Organic Photoredox Catalysts. J Org Chem. 2016;81:7308. - PMC - PubMed
    12. Lang SB, Wiles RJ, Kelly CB, Molander GA. Photoredox Generation of Carbon-Centered Radicals Enables the Construction of 1,1-Difluoroalkene Carbonyl Mimics. Angew Chem Int Ed. 2017;56:15073. - PMC - PubMed
    1. Bonet A, Pubill-Ulldemolins C, Bo C, Gulyás H, Fernández E. Transition-Metal-Free Diboration Reaction by Activation of Diboron Compounds with Simple Lewis Bases. Angew Chem Int Ed. 2011;50:7158. - PubMed
    2. Miralles N, Cid J, Cuenca AB, Carbó JJ, Fernández E. Mixed Diboration of Alkenes in a Metal-Free Context. Chem Commun. 2015;51:1693. - PubMed
    3. Farre A, Soares K, Briggs RA, Balanta A, Benoit DM, Bonet A. Amine Catalysis for the Organocatalytic Diboration of Challenging Alkenes. Chem Eur J. 2016;22:17552. - PubMed
    4. Farre A, Briggs R, Pubill-Ulldemolins C, Bonet A. Developing a Bench-Scale Green Diboration Reaction toward Industrial Application. Synthesis. 2017;49:4775.
    5. Bonet A, Sole C, Gulyás H, Fernández E. Asymmetric Organocatalytic Diboration of Alkenes. Org Biomol Chem. 2012;10:6621. - PubMed
    6. Blaisdell TP, Caya TC, Zhang L, Sanz-Marco A, Morken JP. Hydroxyl-Directed Stereoselective Diboration of Alkenes. J Am Chem Soc. 2014;136:9264. - PMC - PubMed
    7. Fang L, Yan L, Haeffner F, Morken JP. Carbohydrate-Catalyzed Enantioselective Alkene Diboration: Enhanced Reactivity of 1,2-Bonded Diboron Complexes. J Am Chem Soc. 2016;138:2508. - PMC - PubMed
    8. Yan L, Meng Y, Haeffner F, Leon RM, Crockett MP, Morken JP. Carbohydrate/DBU Cocatalyzed Alkene Diboration: Mechanistic Insight Provides Enhanced Catalytic Efficiency and Substrate Scope. J Am Chem Soc. 2018;140:3663. - PMC - PubMed
    9. Morgan JB, Miller SP, Morken JP. Rhodium-Catalyzed Enantioselective Diboration of Simple Alkenes. J Am Chem Soc. 2003;125:8702. - PubMed
    10. Trudeau S, Morgan JB, Shrestha M, Morken JP. Rh-Catalyzed Enantioselective Diboration of Simple Alkenes: Reaction Development and Substrate Scope. J Org Chem. 2005;70:9538. - PubMed
    11. Kliman LT, Mlynarski SN, Morken JP. Pt-Catalyzed Enantioselective Diboration of Terminal Alkenes with B2(pin)2. J Am Chem Soc. 2009;131:13210. - PMC - PubMed
    12. Coombs JR, Haeffner F, Kliman LT, Morken JP. Scope and Mechanism of the Pt-Catalyzed Enantioselective Diboration of Monosubstituted Alkenes. J Am Chem Soc. 2013;135:11222. - PMC - PubMed
    13. Toribatake K, Nishiyama H. Asymmetric Diboration of Terminal Alkenes with a Rhodium Catalyst and Subsequent Oxidation: Enantioselective Synthesis of Optically Active 1,2-Diols. Angew Chem Int Ed. 2013;52:11011. - PubMed
    14. Toribatake K, Nishiyama H, Miyata S, Naganawa Y, Nishiyama H. Asymmetric Synthesis of Optically Active 3-Amino-1,2-Diols from N-Acyl-Protected Allylamines via Catalytic Diboration with Rh[bis(oxazolinyl)phenyl] Catalysts. Tetrahedron. 2015;71:3203.
    1. Sandford C, Aggarwal VK. Stereospecific Functionalizations and Transformations of Secondary and Tertiary Boronic Esters. Chem Commun. 2017;53:5481. - PubMed

Publication types