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使用者:River Shiyu L/沙盒

1,4-dioxygenation of conjugated dienes (1,3-dienes) is the transformation by which a 1,3 diene is converted into a 1,4-diols or 1,4-diacetoxys. This transformation is an oxidative process involving the removal of two electrons and the formation of 2,3 double bonds of 1,3-dienes (Scheme 1).

Scheme 1. 1,4-dioxygenation of dienes

[4+2] cycloadditions with singlet O2

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Scheme 2. 1,4-dioxygenation of dienes

To accomplish this kind of oxidation transformation of 1,3-dienes, [4+2] cycloadditions with singlet O2 is often employed, by forming 1,4-epiperoxides (endoperoxides)(Scheme 2)[1][2]. This overall transformation has long been of interest in prostaglandin chemistry [3][4][5] and applied in natural product synthesis (Scheme 3)[6].

 
Scheme 3. Synthesis application

However, these oxidation transformations, [4+2] cycloadditions of 1,3-dienes with singlet O2, are not easy to be achieved with sufficient selectivity[7][8], and largely remains on substrate-control[9][10].

Besides of cycloaddition with singlet O2, the very established transformations of this kind are accomplished with transition metals (for example, Pd, Pt, etc).

Pd-catalysis

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Pd-catalysis could been divided into two classes: (i) nonoxidation reactions (palladium (0) is the active catalyst) and (ii) oxidation reactions (palladium (II) is the active catalyst). All known reactions of palladium(II) catalysis 1,4-dioxygenation to conjugated dienes (1,3-dienes) are oxidation reactions, which involves nucleophilic attacks on π-diene- and π-allylpalladium complexes and requires external oxidants regenerating active Pd(II) catalysts from Pd(0) species (Scheme 4). The palladium catalysis of 1,4-addition of 1,3-dienes could be an intermolecular or an intramolecular process.[11]

 
Scheme 4. Pd-catalysis 1,4-additions of 1,3-dienes

Intermolecular 1,4-Dioxygenation

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For intermolecular 1,4-dioxygenation, 1,3-dienes react with two nucleophilic anions and loss two electrons to Palladium (II), which later regenerate from Palladium (0) and external oxidants.

 
Scheme 5. Pd-catalysis intermolecular 1,4-additions of 1,3-dienes

Intramolecular 1,4-Dioxygenation

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The 1,4- dioxygenation could also been applied to intramolecular cases. For example, an intramolecular carboxyl group in the side chain of substrate attacks the 1,3-diene to form the 1,4-diacyloxylation product with a newly formed ring.[12][13] The intramolecular 1,4-Diacyloxylation could also be achieved in chemical selective manner by easily changing the ligand environment.

 
Scheme 6. Pd-catalysis intermolecular 1,4-additions of 1,3-dienes

Mechanism

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Typical mechanism and principle of this transformation are given below, the reaction is exemplified with p-benzoquinone (p-BQ) as the oxidant:

 
Scheme 7. Principle and mechanism of Pd Catalysis 1,4-addition of 1,3-dienes

Stereo Outcome

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For most cases, the stereo outcome of 1,4-addition of 1,3-dienes could be easily optimized to give either 1,4-cis or 1,4-trans manner through ligand control, and usually, the crucial ligand which could easily inverse the stereochemical outcome is Cl-. Without the chloride, the acetate will combine with palladium as the counterion, which later migrate from palladium to the carbon. When lithium chloride is present, even a catalytic amount, due to the strong Palladium-Cl bond, the only counterion of palladium is Cl-. Thus, only external attack by the acetate could be achieved which give the 1,4-Cis- result.

 
Scheme 8. Stereo Outcome

This stereo outcome has confirmed by the X-ray of isolated π-allylpalladium complexes.[14]

Pt-catalysis

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In 2002, Kazuko Matsumoto Group observed one example of 1,4-dihydroxylation of 1,3-dienes promoted by the Pt(III) Dinuclear Complex (Scheme 9)[15]. Unfortunately, this transformation requires stoichiometric amount of Pt(III) as oxidant, and regenerates the Pt(III) in site is way difficult.

 
Scheme 9. 1,4-dihydroxylation of 1,3-dienes promoted by the Pt(III) dinuclear complex

In 2009, Morken Group achieved one production of the asymmetric 1,4-diols through one non-directed Pt catalysis way. They applied asymmetric diboration/oxidation sequence to accomplished this kind of transformation (Scheme 10)[16].

 
Scheme 10. Non-directed Pt catalysis 1,4-dihydroxylation of 1,3-dienes

References

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  1. ^ https://www.thieme-connect.com/products/ejournals/abstract/10.1055/s-1974-23462. A Facile One-step Synthesis of cis-2-Cyclopentene- and cis-2-Cyclohexene-1,4-diols from the Corresponding Cyclodienes: 876. 1974. 
  2. ^ Adam, W.; Schenck, G.; Dunlap, D. E. Photosynthese von Cyclopentadien-endoperoxyd bei −100°C und Hydrierung von Endoperoxyden mit Thioharnstoff Verwendung von Na-Dampflampen in der präparativen Photochemie. Angew. Chem. 1956, (68): 248. 
  3. ^ https://www.thieme-connect.com/products/ejournals/abstract/10.1055/s-1974-23462. A Facile One-step Synthesis of cis-2-Cyclopentene- and cis-2-Cyclohexene-1,4-diols from the Corresponding Cyclodienes: 876. 1974. 
  4. ^ Adam, W.; Schenck, G.; Dunlap, D. E. Photosynthese von Cyclopentadien-endoperoxyd bei −100°C und Hydrierung von Endoperoxyden mit Thioharnstoff Verwendung von Na-Dampflampen in der präparativen Photochemie. Angew. Chem. 1956, (68): 248. 
  5. ^ Suglmoto, A.; Eggelte, H. J. 2,3-Dioxabicyclo[2.2.2]octane by Selective Reduction of Double Bonds with Azodicarboxylate. Angew. Chem., Int. Ed. Engl. 1977: 713. 
  6. ^ Jong Seok Lee and Philip L. Fuchs. A Biomimetically Inspired, Efficient Synthesis of the South 7 Hemisphere of Cephalostatin 7. J. Am. Chem. Soc. 2005: 13122-13123. 
  7. ^ Prof. Dr. Rudolf Matusch, Dr. Gerhard Schmidt. Konkurrenz von Endoperoxid- und Hydroperoxidbildung bei der Reaktion von Singulettsauerstoff mit cyclischen, konjugierten Dienen. Angew. Chem. 1988: 729 – 730. 
  8. ^ Steven T. Staben, Xin Linghu, and F. Dean Toste. Enantioselective Synthesis of γ-Hydroxyenones by Chiral Base-Catalyzed Kornblum DeLaMare Rearrangement. J. Am. Chem. Soc. 2006: 12658-12659. 
  9. ^ Jong Seok Lee and Philip L. Fuchs. A Biomimetically Inspired, Efficient Synthesis of the South 7 Hemisphere of Cephalostatin 7. J. Am. Chem. Soc. 2005, 127, 13122-13123. 2005: 13122-13123. 
  10. ^ Jeremy Robertson, Petra M. Stafford, and Stephen J. Bell. Silatropic Carbonyl Ene Cyclizations in the Synthesis of Pseudosugars and Hydroxylated Piperidines. J. Org. Chem. 2005: 7133 – 7148. 
  11. ^ Jan-Erling Backvall. Metal‐Catalyzed Cross‐Coupling Reactions and More, 1, 2 and 3.. 2014. ISBN 9783527331543. 
  12. ^ Backvall, J.E., Andersson, P.G., and Vagberg, J.O. Stereocontrolled lactonization reactions via palladium-catalysis. Tetrahedron Lett. 1989: 137–140. 
  13. ^ Backvall, J.E., Granberg, K.L., Andersson, P.G., Gatti, R., and Gogoll, A. Stereocontrolled lactonization reactions via palladium-catalyzed 1,4-addition to conjugated dienes. J. Org. Chem. 1993, 58, 5445–5451. 1993: 5445–5451. 
  14. ^ Backvall, J.E., Nordberg, R.E., and Wilhelm, D. Dual stereoselectivity in the nucleophilic attack on (.pi.-allyl)palladium complexes. J. Am. Chem. Soc. 1985: 6892–6898. 
  15. ^ Ochiai Masahiko 1 , Matsumoto Kazuko 1. 1,4-Dihydroxylation of 1,3-Conjugated Dienes Promoted by the Pt(III) Dinuclear Complex. CSC Journals. 2002, 31 (3): 270-271. 
  16. ^ Heather E. Burks, Laura T. Kliman, and James P. Morken*. Asymmetric 1,4-Dihydroxylation of 1,3-Dienes by Catalytic Enantioselective Diboration. J. AM. CHEM. SOC. 2009, 131: 9134–9135. 
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