A convenient and highly chemoselective method for the reductive acetylation of azides

Rosen, Terry; Lico, Isabella M.; Chu, Daniel T. W.

doi:10.1021/jo00242a051

Cited by 195 publications

(94 citation statements)

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“…The azido group in ketone (+)-16 was reduced and concomitantly acetylated by thioacetic acid yielding the N-acetamidoketone (+)-31. [22] Using the newly introduced acetamido group as a potential coordination site for the hydride reagent, the ketone (+)-31 could be reduced with either LiBH 4 or NaBD 4 in good yield to the easily separable epimeric alcohols (À)-32 and (+)-34, respectively (À)-33 and (+)-35, wherein at least half of the reduction took place from the concave side. LiBTA C H T U N G T R E N N U N G (OMe) 3 -prepared from reaction of nBuLi, TMEDA with tritium gas to obtain LiT, then reacted with BA C H T U N G T R E N N U N G (OMe) 3 -was used for the tritiation of ketone (+)-31 which afforded alcohol 36 (and its epimer 37).…”

Section: Chemistrymentioning

confidence: 99%

Asymmetric Synthesis and Receptor Pharmacology of the Group II mGlu Receptor Ligand (1S,2R,3R,5R,6S)‐2‐Amino‐3‐hydroxy‐bicyclo[3.1.0]hexane‐2,6‐dicarboxylic Acid—HYDIA

et al. 2008

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The asymmetric synthesis and receptor pharmacology of (1S,2R,3R,5R,6S)-2-amino-3-Hydroxy-bicyclo[3.1.0]hexane-2,6-dicarboxylic Acid (+)-9 (HYDIA) and a few of its O-alkylated derivatives are described. The key step of the synthesis utilizes Sharpless' asymmetric dihydroxylation (AD-beta) for the kinetic resolution of a bicyclic racemic precursor olefin. In contrast to the bicyclic glutamate analogue LY354740, which is a potent and selective agonist for the group II metabotropic glutamate receptors (mGluRs), these new conformationally restricted and also hydroxylated or alkoxylated glutamate analogues are potent and selective antagonists for the group II mGluRs.

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Section: Chemistrymentioning

confidence: 99%

Asymmetric Synthesis and Receptor Pharmacology of the Group II mGlu Receptor Ligand (1S,2R,3R,5R,6S)‐2‐Amino‐3‐hydroxy‐bicyclo[3.1.0]hexane‐2,6‐dicarboxylic Acid—HYDIA

et al. 2008

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“…Therefore only with 6c the acetylation afforded 7 in 77% yield, Scheme 3. 29 In a complementary way, due to our interest in the synthetic applications of enaminones as building block to heterocycles, 30 representative compounds 8a-c were tentatively acetylated, but no reaction was observed at room temperature. Hence, microwave heating was applied, which allowed exclusive formation of N-acylated enaminone 9 from ethyl 3-amino-2-butenoate 8a in yield improved when compared to that previously obtained with acid chloride.…”

Section: Resultsmentioning

confidence: 99%

Eco-Friendly, Catalyst and Solvent-Free, Synthesis of Acetanilides and N-Benzothiazole-2-yl-acetamides

Cunha¹,

Santana²

2016

J. Braz. Chem. Soc.

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An expeditious and green synthesis of acetamides in a solvent-free simple way is described, without catalyst or additives, and in good yield by an instantaneous reaction of anilines or 2-aminothiazoles and acetic anhydride without external heating, and with simple purification. Sixteen substituted acetanilides and four N-benzothiazole-2-yl-acetamides were formed, but aliphatic amines of low molecular weight were not as effective as aromatic ones, and only cyclohexylamine and the enaminone ethyl 3-amino-2-butenoate afforded the corresponding acetamides in good yield.Keywords: acetylation, acetamides, amides, solvente-free reaction, green chemistry IntroductionIn the modern synthetic chemistry the development of greener approaches to the functional group transformations is of continuous interest. 1 There are several ongoing efforts to develop methods which do not need solvent, additives, and without tedious purification. Even reactions carried out without heating and magnetic stirring are relevant contributions, due to the energy economy aspects. 2 The acetamide/acetanilide are functional groups whose importance is beyond of a simple protecting group. For instance, in medicinal chemistry they play a pivotal role affording chemically stable compounds as prodrugs with improved pharmacological profile, and many N-acylated derivatives are in clinical use. 3 On the other hand, acetanilides have natural aptitude to act as ortho directing group in C−H transformations to C−C bond formation, wherein functionalized benzophenone, 4 quinone, 5 bisphenyl, 6 or styrene 7,8 derivatives can be obtained by Pd or Rh catalysis, Figure 1. Besides, the reactivity of some ortho functional group of acetanilides is modulated by the presence of the N-acetyl moiety, which is thus selectively converted to more complex compound, constituting this kind of acetanilide into important synthetic intermediates. 5,[9][10][11][12][13] Due to the abovementioned applications, new developments in the acetylation procedure are still desirables, and representative contributions are described, Figure 2.14-24 Furthermore, in undergraduate courses, the parent acetanilide is extensively synthesized as classical preparation of aromatic amide.25 Therefore, we recently developed a practical solvent-free green synthesis of such compound to experimental courses. 26 However, a search in the literature revealed that when other substituted acetanilides are needed as starting material in the context of a research project, the preparation used is very similar to that of parent acentanilide, which is almost the same of one century ago, which uses large amounts of solvents and additives such as acetic acid and sodium acetate, for instance. [5][6][7][8][9][10][11][12][13][14][15][19][20][21][22][23][24] It should be pointed out that, although there are a few syntheses of acetanilides in the absence of solvent, it is always necessary the use of grinding or microwave heating in these previously described syntheses or, more recurrent, the use of catalyst such as morpholiniu...

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“…As shown in Scheme 3, the levulinoyl group of the disaccharide 27 was removed by simple treatment with NaOMe in MeOH for 2 h to produce 29 in 88 % yield. Reduction and concomitant acetylation of the azide 29 using thioacetic acid [25] 13 C-NMR spectrum of compound 31 indicated that C-1, C-2, C-1' and C-2' appeared at 98.7, 46.2, 99.6 and 79.6 ppm, respectively. The expected downfield shift of the 2'-H signal of 31 relative to its non-sulfated precursor 30 were found to be in good agreement with the literature [26] and clearly indicated the sulfation of O-2'.…”

Section: Resultsmentioning

confidence: 99%

Preparation of a set of selectively protected disaccharides for modular synthesis of heparan sulfate fragments: toward the synthesis of several O-sulfonated [β-D-GlcUA-(1→4)-β-D-GlcNAc]OPr types

Hassan

2005

Open Chemistry

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A concise method for a stereocontrolled synthesis of a set of selectively protected disaccharides is reported. Coupling of the donor 11 onto acceptors 23 and 24, promoted by trimethylsilyl triflate-N-iodosuccinimide (TMSOTf-NIS), generated the disaccharides 25 and 26. Under typical conditions, condensation of the fully protected donor 12 onto acceptors 23 and 24 produced the disaccharides 27 and 28. The building blocks 25–28 were prepared in moderate yields having exclusive β-stereoselectivity. A unique pattern of protecting groups distinguished clearly between positions to be sulfated and functional groups remaining as free hydroxyl groups. Acetyl and/or levulinoyl esters temporarily protected the positions to be sulfated, while benzyl ethers were used for permanent protection. The anomeric positions were protected as allyl ethers, whereas the 4′-positions were masked as p-methoxybenzyl (PMB) ethers. The orthogonality of the PMB and allyl groups can then be used for further elongation of the chain by recurrent deprotection and activation steps. The hydroxyl group, OH-6, of glucosamine moieties was protected as a TBDPS ether to avoid oxidation. A five-step deprotection/sulfonation sequence was applied to the disaccharide 27 to generate the corresponding sulfated [β-D-GlcUA-2-OSO3Na-(1→4)-β-D-Glc pNAc]-(1→O-Pro) 34.

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A convenient and highly chemoselective method for the reductive acetylation of azides

Cited by 195 publications

References 1 publication

Asymmetric Synthesis and Receptor Pharmacology of the Group II mGlu Receptor Ligand (1S,2R,3R,5R,6S)‐2‐Amino‐3‐hydroxy‐bicyclo[3.1.0]hexane‐2,6‐dicarboxylic Acid—HYDIA

Asymmetric Synthesis and Receptor Pharmacology of the Group II mGlu Receptor Ligand (1S,2R,3R,5R,6S)‐2‐Amino‐3‐hydroxy‐bicyclo[3.1.0]hexane‐2,6‐dicarboxylic Acid—HYDIA

Eco-Friendly, Catalyst and Solvent-Free, Synthesis of Acetanilides and N-Benzothiazole-2-yl-acetamides

Preparation of a set of selectively protected disaccharides for modular synthesis of heparan sulfate fragments: toward the synthesis of several O-sulfonated [β-D-GlcUA-(1→4)-β-D-GlcNAc]OPr types

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