Metallorganische Verbindungen, XXV Aluminiumtrialkyle und Dialkyl‐aluminiumhydride als Reduktionsmittel<sup>2)</sup>

“…Unsaturated aldehydes or ketones 4 undergo under these conditions TIBA reduction,21,22 and in situ cyclopropanation of the corresponding aluminum alcoholates. This obviates the need for an independent reduction step, which is often used to prepare the unsaturated alcohol substrates of Table 5, e.g.…”

Section: Resultsmentioning

confidence: 99%

The 2‐Cyano‐2,2‐dimethylethanimine‐N‐oxymethyl Group for the 2′‐Hydroxyl Protection of Ribonucleosides in the Solid‐Phase Synthesis of RNA Sequences

Cieślak¹,

Ausín²,

Grajkowski³

et al. 2013

Chemistry A European J

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The reaction of 2-cyano-2-methyl propanal with 2'-O-aminooxymethylribonucleosides leads to stable and yet reversible 2'-O-(2-cyano-2,2-dimethylethanimine-N-oxymethyl)ribonucleosides. Following N-protection of the nucleobases, 5'-dimethoxytritylation and 3'-phosphitylation, the resulting 2'-protected ribonucleoside phosphoramidite monomers are employed in the solid-phase synthesis of three chimeric RNA sequences, each differing in their ratios of purine/pyrimidine. When the activation of phosphoramidite monomers is performed in the presence of 5-benzylthio-1H-tetrazole, coupling efficiencies averaging 99% are obtained within 180 s. Upon completion of the RNA-chain assemblies, removal of the nucleobase and phosphate protecting groups and release of the sequences from the solid support are carried out under standard basic conditions, whereas the cleavage of 2'-O-(2-cyano-2,2-dimethylethanimine-N-oxymethyl) protective groups is effected (without releasing RNA alkylating side-products) by treatment with tetra-n-butylammonium fluoride (0.5 M) in dry DMSO over a period of 24-48 h at 55 °C. Characterization of the fully deprotected RNA sequences by polyacrylamide gel electrophoresis (PAGE), enzymatic hydrolysis, and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry confirmed the identity and quality of these sequences. Thus, the use of 2'-O-aminooxymethylribonucleosides in the design of new 2'-hydroxyl protecting groups is a powerful approach to the development of a straightforward, efficient, and cost-effective method for the chemical synthesis of high-quality RNA sequences in the framework of RNA interference applications.

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“…Unsaturated aldehydes or ketones 4 undergo under these conditions TIBA reduction, [21,22] and in situ cyclopropanation of the corresponding aluminum alcoholates. This obviates the need for an independent reduction step, which is often used to prepare the unsaturated alcohol substrates of Table 5, e.g.…”

Section: Scope Of the Reactionmentioning

confidence: 99%

Transition‐Metal‐Catalyzed Cyclopropanation of Nonactivated Alkenes in Dibromomethane with Triisobutylaluminum

Brunner¹,

Elmer²,

Schröder³

2011

Eur J Org Chem

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The cyclopropanation of nonactivated alkenes with inexpensive triisobutylaluminum (TIBA), in dibromomethane as solvent and reagent, is efficiently catalyzed by FeCl3 at ambient temperature. Catalytic amounts of CuI salts, CpTiCl3, and [CpFe(CO)2]2 are similarly effective. 2‐Methylpropane, generated after quench of excess TIBA can be trapped, and excess dibromomethane can be recycled, which makes the method industrially applicable. Solvent‐free DIBAH or TIBA reduction of unsaturated carbonyl compounds, followed by in situ TIBA cyclopropanation of the unsaturated aluminum alcoholates in dibromomethane give cyclopropyl alkanols. Dienols such as geraniol, linalool or nor‐radjanol are selectively cyclopropanated in their distal position, which allows the synthesis of flavor and fragrance compounds such as Δ‐citral, cis‐javanol, and 7‐methyl‐georgywood. Uncontrollable exothermic events are avoided due to relatively low reaction temperatures made possible by the catalysts and by the addition mode of the reagents.1

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Metallorganische Verbindungen, XXV Aluminiumtrialkyle und Dialkyl‐aluminiumhydride als Reduktionsmittel²⁾

Cited by 58 publications

References 4 publications

Synthesis of a Multifunctional Oxazolo[5,4-e][1,4]diazepine Skeleton

Synthesis of a Multifunctional Oxazolo[5,4-e][1,4]diazepine Skeleton

The 2‐Cyano‐2,2‐dimethylethanimine‐N‐oxymethyl Group for the 2′‐Hydroxyl Protection of Ribonucleosides in the Solid‐Phase Synthesis of RNA Sequences

Transition‐Metal‐Catalyzed Cyclopropanation of Nonactivated Alkenes in Dibromomethane with Triisobutylaluminum

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Metallorganische Verbindungen, XXV Aluminiumtrialkyle und Dialkyl‐aluminiumhydride als Reduktionsmittel2)

Cited by 58 publications

References 4 publications

Synthesis of a Multifunctional Oxazolo[5,4-e][1,4]diazepine Skeleton

Synthesis of a Multifunctional Oxazolo[5,4-e][1,4]diazepine Skeleton

The 2‐Cyano‐2,2‐dimethylethanimine‐N‐oxymethyl Group for the 2′‐Hydroxyl Protection of Ribonucleosides in the Solid‐Phase Synthesis of RNA Sequences

Transition‐Metal‐Catalyzed Cyclopropanation of Nonactivated Alkenes in Dibromomethane with Triisobutylaluminum

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Product

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Metallorganische Verbindungen, XXV Aluminiumtrialkyle und Dialkyl‐aluminiumhydride als Reduktionsmittel²⁾