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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).
[4+2] cycloadditions with singlet O2
编辑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].
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
编辑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]
Intermolecular 1,4-Dioxygenation
编辑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.
Intramolecular 1,4-Dioxygenation
编辑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.
Mechanism
编辑Typical mechanism and principle of this transformation are given below, the reaction is exemplified with p-benzoquinone (p-BQ) as the oxidant:
Stereo Outcome
编辑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.
This stereo outcome has confirmed by the X-ray of isolated π-allylpalladium complexes.[14]
Pt-catalysis
编辑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.
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].
References
编辑- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ Jan-Erling Backvall. Metal‐Catalyzed Cross‐Coupling Reactions and More, 1, 2 and 3.. 2014. ISBN 9783527331543.
- ^ Backvall, J.E., Andersson, P.G., and Vagberg, J.O. Stereocontrolled lactonization reactions via palladium-catalysis. Tetrahedron Lett. 1989: 137–140.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.