Scope of AuCl3 in the activation of per-O-acetylglycals

Balamurugan, Rengarajan; Koppolu, Srinivasa Rao

doi:10.1016/j.tet.2009.07.087

Cited by 64 publications

(39 citation statements)

References 41 publications

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“…Reaction with 3, 8, and 12 required 5 h, 3 h, and 45 min, respectively, for the complete consumption of the starting materials to form the corresponding products in good to excellent yields ( Table 2, entries 1-3). These are excellent results compared to previous reports, [27] where the same reactions took 16, 12, and 3 h, respectively, and gave much lower yields. Thiophenol (13) produced thioglycoside 36 in 75 % yield in 4.5 h ( Table 2, entry 4).…”

Section: Resultssupporting

confidence: 77%

“…The same reaction has been reported [27] using AuCl 3 alone as a catalyst, but in that case the reaction required 9 h, and led to 18 with a 6.3:1 anomeric ratio ( For comparison purposes, we have listed the yields and selectivities reported in the literature for the reactions using AuCl 3 alone. These results are far better than those obtained in similar reactions with AuCl 3 alone, which required 3.5 h and 16 h. [27] Unsurprisingly, the reaction of tert-butanol was observed to be a bit slower ( reported the formation of 27 using Yb(OTf) 3 (10 mol-%) at room temperature, but this reaction required 18 h for the complete consumption of the starting materials. These results are far better than those obtained in similar reactions with AuCl 3 alone, which required 3.5 h and 16 h. [27] Unsurprisingly, the reaction of tert-butanol was observed to be a bit slower ( reported the formation of 27 using Yb(OTf) 3 (10 mol-%) at room temperature, but this reaction required 18 h for the complete consumption of the starting materials.…”

Section: Resultsmentioning

confidence: 89%

“…The reaction of 1 with thiophenol (13) [27] proceeded smoothly to form thioglycoside 28 in 93 % yield within 5 min (Table 1, entry 11). [27] Carbon Ferrier reactions of glucal 1 were carried out with allyltrimethylsilane 14 and trimethylsilyl cyanide (TMSCN; 15). [27] Carbon Ferrier reactions of glucal 1 were carried out with allyltrimethylsilane 14 and trimethylsilyl cyanide (TMSCN; 15).…”

Section: Resultsmentioning

confidence: 99%

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Gold(III) Chloride and Phenylacetylene: A Catalyst System for the Ferrier Rearrangement, and O‐Glycosylation of 1‐O‐Acetyl Sugars as Glycosyl Donors

et al. 2014

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We have developed a new catalyst system comprising AuCl3 and phenylacetylene that promotes the Ferrier rearrangement of glycals and 2‐acetoxymethylglycals with different nucleophiles, and also the O‐glycosylation of 1‐O‐acetyl sugars to obtain a variety of useful glycosides at room temperature through relay catalysis. Good anomeric selectivity was observed for the Ferrier rearrangements, whereas the O‐glycosylation of 1‐O‐acetyl sugars gave mixtures of diastereomers with moderate to excellent selectivity.

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Section: Resultssupporting

confidence: 77%

Section: Resultsmentioning

confidence: 89%

Section: Resultsmentioning

confidence: 99%

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Gold(III) Chloride and Phenylacetylene: A Catalyst System for the Ferrier Rearrangement, and O‐Glycosylation of 1‐O‐Acetyl Sugars as Glycosyl Donors

et al. 2014

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“…18 The reaction produced the expected compounds in good yields with the α-isomer predominating (Scheme 13).…”

Section: Scheme 11mentioning

confidence: 99%

The carbon-Ferrier rearrangement: an approach towards the synthesis of C-glycosides

Ansari¹,

Lahiri²,

Vankar³

2013

Arkivoc

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The carbon-Ferrier rearrangement is the reaction of appropriately functionalised glycals, with a variety of carbon nucleophiles such as allyltrimethylsilanes, alkynyltrimethylsilanes, silyl cyanides etc. involving the corresponding nucleophilic addition at the anomeric carbon with concomitant loss of a substituent at C-3. This leads to double bond migration to give 2,3-unsaturated sugars which act as useful chiral substrates for further manipulations in organic synthesis.

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“…Once activated, a variety of carbon-based nucleophiles can be utilized,6d including allyltrimethylsilane,11 trimethylsilylcyanide12 and various silyl ketene acetals 13. We utilized silylketene acetal 5 (1-( tert- butyldimethylsilyloxy)-1-methoxyethene) as a nucleophile for generating the C -glycoside as it offers the advantage of installing an ester side chain without further modifications.…”

mentioning

confidence: 99%

Large-Scale Synthesis of All Stereoisomers of a 2,3-Unsaturated C-Glycoside Scaffold

et al. 2011

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All stereoisomers of a highly functionalized 2,3-unsaturated C-glycoside can be accessed in 10-100 g quantities from readily available starting materials and reagents in 3-7 steps. These chiral scaffolds contain three stereogenic centers along with orthogonally protected functional groups for downstream reactivity.Due to their synthetic versatility and high level of stereochemical diversity carbohydrates have served as useful starting points for generating molecular diversity. 1 Carbohydratederived glycals in particular have been employed in multiple diversity-oriented synthesis (DOS) pathways. 2 Of interest to us was the utility of C-alkyl pseudoglycals for developing new build/couple/pair pathways in the context of library development. 3 In the present study, we focused on the synthesis of 2,3-unsaturated C-glycosides 1-4 ( Figure 1) which incorporate four chemical handles: (1) an ester, (2) an alkene, (3) a primary alcohol and (4) a secondary alcohol/primary amine, thereby, providing a range of options for subsequent modifications and/or functional group pairing reactions. 4 As part of our design strategy we sought to develop methods for the preparation of all eight stereoisomers of the C-glycoside template to enable the development of stereo/structure-activity relationships. 3b,5 Herein we describe the preparation of C-glycosides 1-4 on large (>50 g) scale.In order to introduce the ester functionality at C-1 we explored a type I Ferrier rearrangement 6 of tri-O-acetyl-D-and L-glucal to access C-glycosides 1-4. We elected to focus solely on optimizing the large-scale Ferrier reaction for the glucal series with the intention of accessing the galactal-derived material (2) via Mitsunobu inversion of the C-4 allylic alcohol. 7,8 Since we discovered that the α-and β-glycosides could be easily separated by silica gel chromatography and we required access to equal quantities of both anomers, we elected to develop reaction conditions that would achieve a closer to 1:1 α/β ratio.As shown in Table 1, we evaluated the Ferrier reaction of tri-O-acetyl-D-glucal with 5 under a range of conditions, mainly focused on varying the nature of the Lewis acid and solvent. Use of BF 3 ·Et 2 O as the Lewis acid in CH 2 Cl 2 led to the formation of C-glycoside 6 in 45% yield as a 1:2 mixture of anomers favoring the β-anomer (entry 1). Changing the Lewis acid to TMSOTf led to a higher isolated yield (73%) and a more favorable ratio of anomers 1:1.5 (entry 2). Using TMSOTf we next investigated the effect of solvent on reaction selectivity. When employing CH 3 CN as a solvent the formation of the α-anomer was slightly favored (α/β ratio = 1.5:1) and a lower yield was obtained (65%, entry 3). The yield of the glycosidation reaction could be improved to 77% on large scale (200 g), using CH 2 Cl 2 as a co-solvent (entries 4 and 5), providing a 1.2:1 mixture of anomers. The α/β isomers could be easily separated by silica gel chromatography to provide 42% of the α-anomer (α-D-6) and 35% of the β-anomer (β-D-6). 14 Deacetylation an...

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Scope of AuCl3 in the activation of per-O-acetylglycals

Cited by 64 publications

References 41 publications

Gold(III) Chloride and Phenylacetylene: A Catalyst System for the Ferrier Rearrangement, and O‐Glycosylation of 1‐O‐Acetyl Sugars as Glycosyl Donors

Gold(III) Chloride and Phenylacetylene: A Catalyst System for the Ferrier Rearrangement, and O‐Glycosylation of 1‐O‐Acetyl Sugars as Glycosyl Donors

The carbon-Ferrier rearrangement: an approach towards the synthesis of C-glycosides

Large-Scale Synthesis of All Stereoisomers of a 2,3-Unsaturated C-Glycoside Scaffold

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