| 1. |
- Gannimani, Ramesh, et al.
(author)
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Acetal containing polymers as pH-responsive nano-drug delivery systems
- 2020
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In: Journal of Controlled Release. - : Elsevier BV. - 0168-3659 .- 1873-4995. ; 328, s. 736-761
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Research review (peer-reviewed)abstract
- Utilization of unique acidic environment in various disease sites has been quite advantageous in targeted drug delivery. Among the widely explored pH-sensitive moieties such as hydrazone, orthoester, imine, vinylether, etc., the acetal bearing compounds are one of the most explored entities in targeted and improved drug delivery to treat disease conditions at the preclinical stage. This review addresses the design and synthesis of various acetalbased polymers as pH-responsive nano-drug delivery systems in the form of micelles, polymersomes, nanoplexes and polymeric and solid lipid nanoparticles for biomedical applications. The review will identify potential advantages, key challenges and future prospects of acetal-based pH-responsive drug delivery systems. The novel developments, strategies and suggestions described may guide the formulation scientists to optimize acetalbased pH-responsive drug delivery systems as an approach to treat various diseases.
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| 2. |
- Bah, Juho, et al.
(author)
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Carbocations as Lewis Acid Catalysts : Reactivity and Scope
- 2015
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In: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 357:1, s. 148-158
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Journal article (peer-reviewed)abstract
- One class of potential Lewis acids that has received negligible attention as a catalyst is the carbocation. Here we show the potential of triarylmethylium ions as highly powerful Lewis acid catalysts for organic reactions. The Lewis acidity of the triarylmethylium ion can be easily tuned by variation of the electronic properties of the aromatic rings and the catalytic activity of the carbocation is shown to correlate directly to the level of stabilization of the empty p(C)-orbital at the cationic carbon. The versatility of triarylmethylium ions as efficient Lewis acid catalysts for organic reactions is demonstrated in Diels-Alder, aza-Diels-Alder, conjugate addition, halogenation, epoxide rearrangement and intramolecular hetro-ene reactions.
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| 3. |
- Bergström, Maria, et al.
(author)
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N-Iodosuccinimide (NIS) in Direct Aromatic Iodination
- 2017
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In: European Journal of Organic Chemistry. - : Wiley-Blackwell. - 1434-193X .- 1099-0690. ; :22, s. 3234-3239
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Journal article (peer-reviewed)abstract
- N-Iodosuccinimide (NIS) in pure trifluoroacetic acid (TFA) offers a time-efficient and general method for the iodination of a wide range of mono-and disubstituted benzenes at room temperature, as demonstrated in this paper. The starting materials were generally converted into mono-iodinated products in less than 16 hours at room temperature, without byproducts. A few deactivated substrates needed addition of sulfuric acid to increase the reaction rate. Another exception was methoxybenzenes that preferentially were iodinated by NIS in acetonitrile with only catalytic amounts of TFA.
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| 4. |
- Deiana, Luca, et al.
(author)
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Artificial plant cell walls as multi-catalyst systems for enzymatic cooperative asymmetric catalysis in non-aqueous media
- 2021
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In: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 57:70, s. 8814-8817
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Journal article (peer-reviewed)abstract
- The assembly of cellulose-based artificial plant cell wall (APCW) structures that contain different types of catalysts is a powerful strategy for the development of cascade reactions. Here we disclose an APCW catalytic system containing a lipase enzyme and nanopalladium particles that transform a racemic amine into the corresponding enantiomerically pure amide in high yield via a dynamic kinetic resolution.
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| 5. |
- El Remaily, Mahmoud Abd El Aleem Ali Ali, et al.
(author)
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Carbocation Catalysis : Oxa-Diels-Alder Reactions of Unactivated Aldehydes and Simple Dienes
- 2015
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In: European Journal of Organic Chemistry. - : Wiley-VCH Verlagsgesellschaft. - 1434-193X .- 1099-0690. ; :30, s. 6610-6614
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Journal article (peer-reviewed)abstract
- The versatility of the trityl cation (TrBF4) as a highly efficient Lewis acid organocatalyst is demonstrated in the oxa-Diels-Alder reaction of various unactivated aromatic and aliphatic aldehydes and simple unactivated dienes, such as isoprene and 2,3-dimethylbutadiene. The transformation proceeds smoothly to give 3,6-dihydropyrane adducts in high to moderate yields with catalyst loadings down to 1.0 mol-% under mild reaction conditions. In contrast to most previously reported strategies, this protocol does not require substrate functional group activation, neither by electron-deficient aldehydes (2-oxo aldehydes) or electron-rich dienes (methoxy or amino-butadiene).
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| 6. |
- Naidu, Veluru Ramesh, et al.
(author)
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Direct Organocatalytic Oxo-Metathesis, a trans-Selective Carbocation-Catalyzed Olefination of Aldehydes
- 2015
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In: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; :8, s. 1834-1839
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Journal article (peer-reviewed)abstract
- A direct organocatalytic carbonyl/olefin oxo-metathesis has been developed. The reaction is catalyzed by trityl tetrafluoroborate (TrBF4) and utilizes unactivated alkenes for the olefination of aromatic aldehydes to give trans -alkylstyrenes in yields of 44-85% with only acetone as the byproduct. The pronounced Lewis acidity of the carbocation results in unusual reactivity that is proposed to catalyze a stepwise [2+2] cycloaddition to give an oxetane intermediate. Fragmentation of the latter in a formal retro [2+2] reaction gives the oxo-metathesis product.
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| 7. |
- Naidu, Veluru Ramesh, et al.
(author)
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Selective Cascade Reaction of Bisallenes via Palladium-Catalyzed Aerobic Oxidative Carbocyclization-Borylation and Aldehyde Trapping
- 2017
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In: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 56:6, s. 1590-1594
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Journal article (peer-reviewed)abstract
- A cascade reaction, consisting of a palladium-catalyzed regioselective aerobic oxidative carbocyclization-borylation of bisallenes and a final aldehyde trapping, afforded triene alcohols with high diastereoselectivity. The cascade reaction occurs under mild reaction conditions and proceeds via an allylboron intermediate that is trapped by the aldehyde in a stereoselective manner.
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| 8. |
- Naidu, Veluru Ramesh, et al.
(author)
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Synthesis of Cross-Conjugated Polyenes via Palladium-Catalyzed Oxidative C-C Bond Forming Cascade Reactions of Allenes
- 2020
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In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 85:8, s. 5428-5437
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Journal article (peer-reviewed)abstract
- An efficient palladium-catalyzed oxidative C-C bond forming cascade reaction of allenes involving a coupling between an enallene and an allenyne followed by a carbocyclization of the generated Pd-intermediate was developed. This cascade reaction afforded functionalized cross-conjugated polyenes. The enallene is initially activated by palladium and reacts with the allenyne to give the cross-conjugated polyenes.
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| 9. |
- Naidu, Veluru Ramesh, et al.
(author)
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The Carbocation : A Forgotten Lewis Acid Catalyst
- 2015
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In: ChemCatChem. - : Wiley. - 1867-3880 .- 1867-3899. ; 7:13, s. 1896-1905
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Journal article (peer-reviewed)abstract
- A Lewis acid that has received negligible attention as a catalyst is the carbocation. The carbocation is isoelectronic to boron and owes its Lewis acidity to a low-lying empty p(C) orbital. In terms of reactivity and stability carbocations are very versatile Lewis acids, from the extremely unstable methylium cation to the water-stable tris(N,N-dimethylaniline) methylium ion (crystal violet). Although the Lewis acid properties of carbocations have been extensively studied since the discovery of the tropolium ion more than 130years ago there is only a handful examples on the application of carbocations as Lewis acid catalysts. Herein, the research on triarylmethylium (trityl)-cation catalysis is summarized. In light of the reports the trityl ion emerges as a highly efficient and highly versatile Lewis acid catalyst capable of catalyzing different classes of reactions often with high selectivity and low catalyst loadings (for some reactions down to ppm levels).
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| 10. |
- Ni, Shengjun, et al.
(author)
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Chiral Anion Directed Asymmetric Carbocation-Catalyzed Diels-Alder Reactions
- 2016
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In: European Journal of Organic Chemistry. - : Wiley-VCH Verlagsgesellschaft. - 1434-193X .- 1099-0690. ; :9, s. 1708-1713
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Journal article (peer-reviewed)abstract
- In recent years the carbocation has re-emerged as a highly efficient Lewis acid catalyst for a variety of organic transformations. However, the goal of asymmetric carbocation catalysis has so far been out of reach mainly as a result of difficulties associated with the preparation of stable chiral carbocations. Here, we describe developments towards asymmetric carbocation catalysis based on the concept of chiral-anion-directed catalysis. Chiral tritylium salts can be conveniently prepared in situ by mixing trityl chloride derivatives with chiral phosphonate, phosphoramide, bis(sulfonyl) amide, and bis(sulfuryl) amide silver or sodium salts. It is shown that the bis(sulfuryl) amide/tritylium ion salt catalyzes the Diels-Alder reaction with an up to 53 % enantiomeric excess.
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