Photoredox Catalyzed Ring-Opening Addition Reaction Between Benzyl Bromides and Cyclic Ethers

Synthesis ◽  
2021 ◽  
Author(s):  
Cuiwen Kuang ◽  
Chuanfa Ni ◽  
Yucheng Gu ◽  
Jinbo Hu
Keyword(s):  
Ring Opening ◽  
Addition Reaction ◽  
Benzyl Bromide ◽  
Addition Product ◽  
Cyclic Ether ◽  
Cyclic Ethers ◽  
Single Electron Transfer ◽  
Nucleophilic Reaction ◽  
Reaction Proceeds ◽  
Bromide Ion

A novel nucleophilic reaction between cyclic ethers and benzyl bromides is achieved under photoredox catalysis. The reaction proceeds through a single electron transfer (SET) pathway rather than a common SN2 mechanism. By two steps of reduction and oxidation, a benzyl bromide heterolyzes to give a carbocation and bromide ion under mild conditions, and then a cyclic ether captures both the carbocation and bromide ion to afford the addition product.

The Rychnovsky Synthesis of Leucascandrolide A

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Vinyl Ether ◽  
Absolute Configuration ◽  
Secondary Alcohol ◽  
Primary Alcohol ◽  
Addition Product ◽  
Cyclic Ether ◽  
Acid Activation ◽  
Leucascandrolide A ◽  
Stereogenic Centers ◽  
Bromide Ion

The macrolactone leucascandrolide A 4, isolated from the calcareous sponge L. caveolata, has both cytotoxic and antifungal activity. The key step in the synthesis of 4 reported (J. Org. Chem. 2007, 72, 5784) by Scott D. Rychnovsky of the University of California, Irvine, was the stereoselective condensation of the aldehyde 1 with the allyl vinyl ether 2 to give 3. The cyclic ether of 1 was assembled from the crotyl addition product 5. Tandem Ru-catalyzed metathesis/hydrogenation converted 5 to the lactone 6. Reduction of 6 to the lactol followed by activation as the acetate gave 7, axial-selective condensation of which with the enol ether 8 delivered the enone 9. Diastereoselective Itsuno-Corey reduction of 9 followed by protecting group exchange and oxidation then gave 1, containing four of the eight stereogenic centers of leucascandrolide A 4. The vinyl ether 2 was readily prepared from the corresponding homoallylic alcohol. Condensation of 1 with 2 involved Lewis acid activation of the aldehyde, addition of the resulting carbocation to the vinyl ether, and cyclization with trapping by bromide ion. In this process, the other four of the eight stereogenic centers were assembled. Three of those centers were formed in the course of the reaction. While stereocontrol was not perfect, the route is pleasingly succinct, so practical quantities of diastereomerically pure 3 could be prepared. To complete the synthesis, the secondary alcohol of 3 was methylated. Selective desilyation of the primary alcohol followed by oxidation and desilylation then set the stage for the Mitsunobu macrolactonization. The intermediates in the Mitsunobu reaction are such that the lactonization can proceed with either inversion of absolute configuration at the secondary center, or retention. While the usually-employed Ph3P gave the lactone with retention of absolute configuration, Bu3P led to clean inversion. The last challenge was the establishment of the (Z) alkene of the side chain. This was accomplished using the Toru protocol. Coupling of the secondary bromide with the Cs salt 12 proceeded with inversion of absolute configuration, to give 13.

Visible Light-Promoted Catalytic Ring-Opening Isomerization of 1,2-Disubstituted Cyclopropanols to Linear Ketones

2019 ◽  
Author(s):  
Marharyta V. Laktsevich-Iskryk ◽  
Nastassia A. Varabyeva ◽  
Volha V. Kazlova ◽  
Vladimir N. Zhabinskii ◽  
Vladimir A. Khripach ◽  
...  
Keyword(s):  
Visible Light ◽  
Functional Groups ◽  
Ring Opening ◽  
Radical Intermediates ◽  
Reaction Proceeds

In this article, we report a photocatalytic protocol for the isomerization of 1,2-disubstituted cyclopropanols to linear ketones. The reaction proceeds <i>via</i> radical intermediates and tolerates various functional groups.

Visible Light-Promoted Catalytic Ring-Opening Isomerization of 1,2-Disubstituted Cyclopropanols to Linear Ketones

2019 ◽  
Author(s):  
Marharyta V. Laktsevich-Iskryk ◽  
Nastassia A. Varabyeva ◽  
Volha V. Kazlova ◽  
Vladimir N. Zhabinskii ◽  
Vladimir A. Khripach ◽  
...  
Keyword(s):  
Visible Light ◽  
Functional Groups ◽  
Ring Opening ◽  
Radical Intermediates ◽  
Reaction Proceeds

In this article, we report a photocatalytic protocol for the isomerization of 1,2-disubstituted cyclopropanols to linear ketones. The reaction proceeds <i>via</i> radical intermediates and tolerates various functional groups.

Metal Doped-C3N4/Fe2O4: Efficient and Versatile Heterogenous Catalysts for Organic Transformations

2019 ◽  
Vol 23 (12) ◽  
pp. 1284-1306
Author(s):  
Vijai K. Rai ◽  
Fooleswar Verma ◽  
Suhasini Mahata ◽  
Smita R. Bhardiya ◽  
Manorama Singh ◽  
...  
Keyword(s):  
Ring Opening ◽  
Carbon Nitride ◽  
Addition Reaction ◽  
High Surface ◽  
Graphitic Carbon ◽  
Graphitic Carbon Nitride ◽  
Organic Transformations ◽  
Reduction Reactions ◽  
Activation Reaction ◽  
Metal Doped

The polymeric graphitic carbon nitride (g-C3N4) has been one of the interesting earth abundant elements. Though g-C3N4 finds application as a photocatalyst, its photocatalytic behaviour is limited because of low efficiency, mainly due to rapid charge recombination. To overcome this problem, several strategies have been developed including doping of metal/non-metal in the cavity of g-C3N4. Moreover, the CoFe2O4 NPs have been used in many organic transformations because of its high surface area and easy separation due to its magnetic nature. This review describes the role of cobalt ferrite as magnetic nanoparticles and metal-doped carbon nitride as efficient heterogeneous catalysts for new carbon-carbon and carbon-hetero atom bond formation followed by heterocyclization. Reactions which involved new catalysts for selective activation of readily available substrates has been reported herein. Since nanoparticles enhance the reactivity of catalyst due to higher catalytic area, they have been employed in various reactions such as addition reaction, C-H activation reaction, coupling reaction, cyclo-addition reaction, multi-component reaction, ring-opening reaction, oxidation reaction and reduction reactions etc. The driving force for choosing this topic is based-on huge number of good publications including different types of spinels/metal doped-/graphitic carbon nitride reported in the literature and due to interest of synthetic community in recent years. This review certainly will represent the present status in organic transformation and for exploring further their catalytic efficiency to new organic transformations involving C-H activation reaction through coupling, cyclo-addition, multi-component, ring-opening, oxidation and reduction reactions.

Participation of 19-substituents in electrophilic additions to 6,7-unsaturated 5α-cholestane and B-homo 5α-cholestane derivatives; A case of competition between the participation of an ambident neighboring group and external nucleophile attack

1980 ◽  
Vol 45 (2) ◽  
pp. 559-583 ◽  
Author(s):  
Pavel Kočovský ◽  
Ladislav Kohout ◽  
Václav Černý
Keyword(s):  
Perchloric Acid ◽  
Hydrobromic Acid ◽  
Cyclic Ether ◽  
Cyclic Ethers ◽  
Neighboring Group ◽  
Acid Cleavage ◽  
Neighbouring Group Participation ◽  
Aqueous Perchloric Acid ◽  
The Difference ◽  
Electrophilic Additions

Hypobromous acid action upon the 6,7-unsaturated 19-substituted 5α-cholestans Va-Vc results in the formation of two types of products, the cyclic ethers IX as products of 5(O)n participation of the 19-substituent, and the bromohydrins X. All these compounds are formed from the 6α,7α-bromonium ions Va'-Vc'. Under the same conditions the B-homo-5α-cholestane derivatives VIIa-VIIc afforded solely the cyclic ethers XIV as products of 5(O)n participation of the 19-substituent in the cleavage of the bromonium ions VIIa'-VIIc'. Acid cleavage of the 6α,7α-epoxides VIb and VIc with aqueous perchloric acid or hydrobromic acid gave two types of products, i.e. the cyclic ethers XI and the diols XII or bromohydrines XIII. The cyclic ethers XI arise by 5(O)n participation of the 19-substituent. The B-homo-6α, 7α-epoxide VIIIc on cleavage with aqueous perchloric acid have solely the cyclic ether XVc and by treatment with hydrobromic acid VIIIc afforded the mixture of XVc, as the main product, and of the bromohydrin XVIc. Discussed is the similarity of the bromonium ion cleavage with the fission of the corresponding epoxides, the mechanism of these reactions and the difference in the behaviour of the isomeric olefins Ia-c, IIIa-c, Va-c and VIIa-c and epoxides IIb,c, IVb,c, VIb,c and VIIIb,c. The competition between ambident neighbouring group participation and external nucleophile attack is discussed as well as the dependence of the products ratio on the nucleophilicity of the attacking species.

Reactions of 4-Pyrones with Azomethine Ylides as a Chemo­selective Method for the Construction of Multisubstituted Pyrano[2,3-c]pyrrolidines

Synthesis ◽  
2021 ◽  
Author(s):  
Dmitrii L. Obydennov ◽  
Vyacheslav D. Steben’kov ◽  
Konstantin L. Obydennov ◽  
Sergey A. Usachev ◽  
Vladimir S. Moshkin ◽  
...  
Keyword(s):  
Double Bond ◽  
Ring Opening ◽  
Azomethine Ylides ◽  
Azomethine Ylide ◽  
Dipolar Cycloaddition ◽  
Computational Studies ◽  
Carbon Double Bond ◽  
Reactivity Indexes ◽  
Reaction Proceeds

Abstract4-Pyrones bearing electron-donating and electron-withdrawing groups react with nonstabilized azomethine ylides to form pyrano[2,3-c]pyrrolidines in moderate to good yields. The reaction proceeds chemoselectively as a 1,3-dipolar cycloaddition of the azomethine ylide at the carbon–carbon double bond of the pyrone activated by the electron-withdrawing substituent. The reactivity of 4-pyrones toward azomethine ylides was rationalized by computational studies with the use of reactivity indexes. The pyrano[2,3-c]pyrrolidine moiety could be modified, for example by a ring-opening transformation under the action of hydrazine to provide pyrazolyl-substituted pyrrolidines.

Tandem Alkylation/Michael Addition Reaction of Dithiocarbamic Acids with Alkyl γ-Bromocrotonates: Access to Functionalized 1,3-Thiazolidine-2-thiones

Synthesis ◽  
2021 ◽  
Author(s):  
Azim Ziyaei Halimehjani ◽  
Petr Beier ◽  
Maryam Khalili Foumeshi ◽  
Ali Alaei ◽  
Blanka Klepetářová
Keyword(s):  
Amino Acids ◽  
Carbon Disulfide ◽  
Multicomponent Reaction ◽  
Michael Addition ◽  
Addition Reaction ◽  
Primary Amines ◽  
Oxidation Reactions ◽  
Michael Addition Reaction ◽  
Synthetic Utility ◽  
Reaction Proceeds

AbstractThiazolidine-2-thiones were prepared via a novel multicomponent reaction of primary amines (amino acids), carbon disulfide, and γ-bromocrotonates. The reaction proceeds via a domino alkylation/intramolecular Michael addition to provide the corresponding thiazolidine-2-thiones in high to excellent yields. By using diamines in this protocol, bis(thiazolidine-2-thiones) derivatives were synthesized. The synthetic utility of the adducts was demonstrated by hydrolysis, amidation, and oxidation reactions.

Ring-opening polymerization of cyclic ethers initiated by benzazaphosphole-W(CO)5/silver hexafluoroantimonate

2013 ◽  
Vol 52 (5) ◽  
pp. 664-670 ◽  
Author(s):  
Mohammed Ghalib ◽  
Sergej Lysenko ◽  
Peter G. Jones ◽  
Joachim W. Heinicke
Keyword(s):  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Cyclic Ethers

TiCp2Cl-Catalyzed Living Radical and Ring Opening Polymerizations Initiated from Epoxides and Aldehydes in the Synthesis of Linear, Graft and Branched Polymers

2004 ◽  
Vol 856 ◽  
Author(s):  
Alexandru D. Asandei ◽  
Isaac W. Moran ◽  
Gobinda Saha ◽  
Yanhui Chen
Keyword(s):  
Electron Transfer ◽  
Ring Opening ◽  
Glycidyl Methacrylate ◽  
Ring Opening Polymerization ◽  
Branched Polymers ◽  
Single Electron Transfer ◽  
Radical Ring ◽  
Polymer Architectures ◽  
Complex Polymer

ABSTRACTTi(III)Cp2Cl-catalyzed radical ring opening (RRO) of epoxides or single electron transfer (SET) reduction of aldehydes generates Ti alkoxides and carbon centered radicals which add to styrene, initiating a radical polymerization. This polymerization is mediate in a living fashion by the reversible termination of growing chains with the TiCp2Cl metalloradical. In addition, polymers or monomers containing pendant epoxide groups (glycidyl methacrylate) can be used as substrates for radical grafting or branching reactions by self condensing vinyl polymerization. In addition, Ti alkoxides generated in situ by both epoxide RRO and aldehyde SET initiate the living ring opening polymerization of ε-caprolactone. Thus, new initiators and catalysts are introduced for the synthesis of complex polymer architectures.

Ring-opening spontaneous alternating copolymerization of a dithiadiphosphetane disulfide with cyclic ethers

1983 ◽  
Vol 10 (11-12) ◽  
pp. 491-496 ◽  
Author(s):  
Shiro Kobayashi ◽  
Tak Yuen Chow ◽  
Takeo Saegusa
Keyword(s):  
Ring Opening ◽  
Cyclic Ethers ◽  
Alternating Copolymerization
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