Äthylen‐rhodanhydrin

Wagner‐Jauregg, Th.

doi:10.1002/jlac.19495610202

Cited by 21 publications

(11 citation statements)

References 2 publications

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“…A second method employs the addition of thiocyanic acid, generated in situ at low temperature, to the epoxide [18 -21]. It has been reported for these syntheses that the presence of some hydroquinone (¼ benzene-1,4-diol) or DDQ (¼ 4,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,2-dicarbonitrile) is required to stabilize the produced b-hydroxy thiocyanate and to inhibit its conversion to thiirane [16] [22]. Although the reagents such as Ti(O i Pr) 4 [23], Ph 3 P · (SCN) 2 [24], TiCl 3 (or ZnCl 2 ) [25], and [Pd(PPh 3 ) 4 ] [26] are useful, they are limited to specific oxiranes and are not applicable as versatile reagents in the preparation of b-hydroxy thiocyanates [27].…”

mentioning

confidence: 99%

Synthesis of Some Novel Thioxanthenone‐Fused Azacrown Ethers, and Their Use as New Catalysts in the Efficient, Mild, and Regioselective Conversion of Epoxides to β‐Hydroxy Thiocyanates with Ammonium Thiocyanate

Sharghi

Beni

Khalifeh

2007

Helvetica Chimica Acta

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The regioselective ring-opening reactions of some epoxides with ammonium thiocyanate in the presence of a series of new 9H-thioxanthen-9-one-fused azacrown ethers, i.e., 7 -11 (Scheme 1), and also of dibenzo [18]crown-6 (12), Kryptofix 22 (13), and benzo[15]crown-5 (14) were studied ( Tables 1 and 2). The epoxides were subjected to cleavage by NH 4 SCN in the presence of these catalysts under mild conditions in various aprotic solvents. Reagents and conditions were identified for the synthesis of individual b-hydroxy thiocyanates in high yield and with more than 90% regioselectivity. The results can be discussed in terms of a four-step mechanism (Scheme 2): 1) formation of a complex between catalyst and NH 4 SCN, 2) release of SCN À from the complex, 3) reaction of the released SCN À at the sterically less hindered site of the epoxide, and 4) regeneration of the catalyst. The major advantages of this method are the high regioselectivity, the simple regeneration of the catalyst, the reuse of it through several cycles without a decrease of activity, and the ease of workup of the reaction mixtures.Introduction. -Epoxides are one of the most versatile intermediates in organic synthesis, and a large variety of reagents are known for the ring opening of these compounds [1]. Their electrophilic reaction with different nucleophiles has been a permanent subject in organic synthesis [2 -7]. Among these nucleophiles, the reaction of the thiocyanate ion with epoxides, in the absence or in the presence of a catalyst, is a widely studied and suitable method for the preparation of thiiranes [8 -15]. The formation of thiiranes from the reaction of epoxides and thiocyanate ions has been proposed to occur through the intermediacy of the corresponding b-hydroxy thiocyanate, but this intermediate has not been isolated due to its rapid conversion to the corresponding thiirane [13 -17]. There are two methods reported in the literature for the synthesis of b-hydroxy thiocyanates. In one method, thiocyanohydrins are prepared by opening of a cyclic sulfate with NH 4 SCN to form the corresponding bsulfate, which is then hydrolyzed to the thiocyanohydrines. A second method employs the addition of thiocyanic acid, generated in situ at low temperature, to the epoxide [18 -21]. It has been reported for these syntheses that the presence of some hydroquinone (¼ benzene-1,4-diol) or DDQ (¼ 4,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,2-dicarbonitrile) is required to stabilize the produced b-hydroxy thiocyanate and to inhibit its conversion to thiirane [16] [22]. Although the reagents such as Ti(O

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confidence: 99%

Synthesis of Some Novel Thioxanthenone‐Fused Azacrown Ethers, and Their Use as New Catalysts in the Efficient, Mild, and Regioselective Conversion of Epoxides to β‐Hydroxy Thiocyanates with Ammonium Thiocyanate

Sharghi

Beni

Khalifeh

2007

Helvetica Chimica Acta

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“…This method uses the addition of thiocyanic acid generated in situ at low temperature [6,7] or thiocyanate salts in catalyst-free conditions [8] or in the presence of various catalysts, such as tetrabutylammonium fluoride, [9] titanium isopropoxide, [10] triphenylphosphine-thiocyanogen (TPPT), [11] titanium, zinc, and gallium chlorides, [12,13] triphenylphosphinepalladium, [14] crown ethers, [15] polyacryloamides, [16] selectfluor, [17] 2-phenyl-2-(pyridyl)imidazolidine (PPI), [18] 2,6-bis[2-(o-aminophenoxy)-methyl]-4-bromo-1-methoxybenzene (BABMB), [19] Schiff-base metal (II) complexes, [20] metalloporphyrins, [21] or tetraarylporphyrins. [22] According to the literature data, [6,23] b-hydroxy thiocyanates are not stable, and the presence of traces of hydroquinone or 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) stabilize them and slow down their rapid conversion into thiiranes. In recent papers, [24,25] we have described a possibility of transforming b-hydroxy thiocyanates into appropriate acetates by reaction with acetyl chloride.…”

Section: Simple Synthesis Of β-Acetoxy Thiocyanates From Oxiranesmentioning

confidence: 99%

“…ŁUKOWSKA-CHOJNACKA AND J. PLENKIEWICZ used as the catalyst. We also checked the earlier [6] suggestion that addition of a trace amount of hydroquinone stabilizes the formed b-hydroxy thiocyanates 2. The reactions were carried out with and without the addition of hydroquinone.…”

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confidence: 99%

Simple Synthesis of β-Acetoxy Thiocyanates from Oxiranes

Łukowska-Chojnacka

Plenkiewicz

2011

Synthetic Communications

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“…The Wagner‐Jauregg reaction (Scheme 1), [ 1,2 ] discovered just 2 years after the closely related Diels–Alder reaction, [ 3 ] is a potentially powerful tool for synthetic organic chemistry. Starting from three planar molecules, this reaction allows the construction of four new C–C bonds, two new rings, and up to eight new stereocenters in a single synthetic step, granting easy access to complex, polycyclic small molecules.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic and computational evidence for the concerted mechanism of the Wagner‐Jauregg reaction

Tartakoff

Enders

Zhang

et al. 2020

J of Physical Organic Chem

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The Wagner-Jauregg reaction, despite its potential utility, has remained largely unexplored since its discovery in 1930. Utilizing density functional theory (DFT) calculations and experimental 1 H nuclear magnetic resonance (NMR) kinetics data to generate a Hammett plot, the reaction is shown to proceed via a highly asynchronous, concerted mechanism, analogous to the Diels-Alder reaction. Our development of milder, more reliable reaction conditions for the Wagner-Jauregg reaction will facilitate the synthesis of novel, structurally complex, polycyclic molecules.

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Äthylen‐rhodanhydrin

Cited by 21 publications

References 2 publications

Synthesis of Some Novel Thioxanthenone‐Fused Azacrown Ethers, and Their Use as New Catalysts in the Efficient, Mild, and Regioselective Conversion of Epoxides to β‐Hydroxy Thiocyanates with Ammonium Thiocyanate

Synthesis of Some Novel Thioxanthenone‐Fused Azacrown Ethers, and Their Use as New Catalysts in the Efficient, Mild, and Regioselective Conversion of Epoxides to β‐Hydroxy Thiocyanates with Ammonium Thiocyanate

Simple Synthesis of β-Acetoxy Thiocyanates from Oxiranes

Spectroscopic and computational evidence for the concerted mechanism of the Wagner‐Jauregg reaction

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