Protection for the Hydroxyl Group, Including 1,2‐ and 1,3‐Diols

doi:10.1002/9781118905074.ch02

Cited by 8 publications

(1 citation statement)

References 3,160 publications

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“…The silyl derivative 4f was prepared by silylation of vinyl gallate and the benzylated derivative 4g was prepared by transesterification of 3,4,5-tribenzylgallic acid with vinyl acetate. Silyl and benzyl protective groups are widely used in the syntheses, as they can be effectively removed under mild, relatively neutral conditions [ 67 ].…”

Section: Resultsmentioning

confidence: 99%

From Hamamelitannin Synthesis to the Study of Enzymatic Acylations of D-Hamamelose

Mastihubová

Mastihuba

2023

Biomolecules

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The bioactive natural substance, hamamelitannin, was effectively synthesized in two ways. The chemical acylation of 2,3-O-isopropylidene-α,β-D-hamamelofuranose promoted by Bu2SnO using 3,4,5-tri-O-acetylgalloyl chloride, followed by the deprotection provided hamamelitannin in 79%. Pilot enzymatic benzoylation of D-hamamelose using vinyl benzoate (4 equiv.) and Lipozyme TL IM as a biocatalyst in t-butyl methyl ether (t-BuMeO) gave mainly benzoylated furanoses (89%), of which tribenzoates reached (52%). Enzymatic galloylation of 2,3-O-isopropylidene-α,β-D-hamamelofuranose with vinyl gallate under the catalysis of Lipozyme TL IM in t-butyl alcohol (t-BuOH) or t-BuMeO provided only the 5-O-galloylated product. The reaction in t-BuMeO proceeded in a shorter reaction time (61 h) and higher yield (82%). The more hydrophobic vinyl 3,4,5-tri-O-acetylgallate in the same reactions gave large amounts of acetylated products. Vinyl gallate and triacetylgallate in the enzymatic acylation of D-hamamelose with Lipozyme TL IM in t-BuMeO yielded 2′,5-diacylated hamamelofuranoses in a yield below 20%. The use of other vinyl gallates hydrophobized by methylation or benzylation provided 2′,5-diacylated hamamelofuranoses in good yields (65–84%). The reaction with silylated vinyl gallate did not proceed. The best results were obtained with vinyl 2,3,5-tri-O-benzyl gallate, and the only product, 2′,5-diacylated hamamelofuranoside precipitated from the reaction mixture (84% in 96 h). After debenzylation, hamamelitannin was obtained an 82% yield from hamamelose in two steps. This synthesis is preparatively undemanding and opens the way to multigram preparations of bioactive hamamelitannin and its analogues.

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Section: Resultsmentioning

confidence: 99%

From Hamamelitannin Synthesis to the Study of Enzymatic Acylations of D-Hamamelose

Mastihubová

Mastihuba

2023

Biomolecules

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An Eco‐Friendly and Switchable Carbon‐Based Catalyst for Protection‐Deprotection of Vicinal Diols

et al. 2023

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Even though protection-free protocols represent a key principle of green chemistry, both protection and deprotection routes are indispensable strategies in synthetic pursuits, especially towards highly functionalized pharmaceuticals and agrochemicals, often decorated by promiscuous OH or NH groups, among others. Herein a sustainable carbon-based catalyst is reported that efficiently promotes the protection of 1,2-diols as isopropylidene ketals under heterogeneous conditions, affording products in high conversion and yields. Grafting of sulfonate groups onto the high-surface-area carbon creates a solid acid catalyst with high performance for acetalization under mild thermal conditions. Interestingly, the same catalyst can be employed for the inverse deprotection step leading to the parent diols with comparable efficiency. Along with a detailed catalyst's characterization, critical issues related to catalyst loading, reaction scope, and selectivity were thoroughly optimized. The catalyst can be recycled, and no impurities caused by leaching could be observed.

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Iron‐Catalyzed Alkoxylation, Dehydrogenative‐Polymerization and Tandem Hydrosilylative‐Alkoxylation

Sen

Kumar

Tewari

et al. 2023

Chemistry A European J

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Alkoxylation, hydrosilylative-alkoxylation, and dehydrogenative-polymerization are some of the most widely used transformations in synthetic chemistry. However, these transformations are traditionally catalyzed by precious, and rare late-transition metals. Presented here is a molecularly defined iron complex that catalyzes alkoxylation, tandem hydrosilylative-alkoxylation, and dehydrogenative polymerization of silanes under mild conditions. The iron complex [Fe(CO) 4 (H)(SiPh 3 )] 1 catalyzes a direct SiÀ O coupling reaction between an array of silanes and alcohols to produce desired alkoxysilanes in excellent yield, with H 2 as the only byproduct.The iron catalyst tolerates various functional groups and provides access to 20 alkoxysilanes, including essential molecules such as β-citronellol and cholesterol. Further, complex 1 catalyzes the polymerization of renewable diol and silane monomer to produce a renewable and degradable poly(isosorbideÀ silyl ether). Remarkably, complex 1 catalyzes a tandem hydrosilylative-alkoxylation of alkynes under mild conditions to yield unsaturated silyl ethers. The synthetic utility has been demonstrated by gram-scale alkoxylation and hydrosilylative-alkoxylation reactions.

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Protection for the Hydroxyl Group, Including 1,2‐ and 1,3‐Diols

Cited by 8 publications

References 3,160 publications

From Hamamelitannin Synthesis to the Study of Enzymatic Acylations of D-Hamamelose

From Hamamelitannin Synthesis to the Study of Enzymatic Acylations of D-Hamamelose

An Eco‐Friendly and Switchable Carbon‐Based Catalyst for Protection‐Deprotection of Vicinal Diols

Iron‐Catalyzed Alkoxylation, Dehydrogenative‐Polymerization and Tandem Hydrosilylative‐Alkoxylation

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