DDQ CATALYSES THE CONVERSION OF EPOXIDES TO ß-HYDROXY THIOCYANATES WITH NH<sub>4</sub>SCN

Iranpoor, Nasser; Kohmareh, G.

doi:10.1080/10426509908031625

Cited by 27 publications

(8 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…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

View full text Add to dashboard Cite

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

show abstract

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

View full text Add to dashboard Cite

show abstract

“…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: 98%

Simple Synthesis of β-Acetoxy Thiocyanates from Oxiranes

Łukowska-Chojnacka

Plenkiewicz

2011

Synthetic Communications

View full text Add to dashboard Cite

“…2-Hydroxy-2-phenylethyl thiocyanate (2a) 7,12 . IR (neat): n SCN (2160 cm À1 ); 1 HNMR (CDCl 3 , 250 MHz) d ¼ 7.3 (5H, m), 5.0 (1H, dd), 3.1-3.3 (2H, m), 2.4-2.9 (1H, br s).…”

Section: Experimental Generalmentioning

confidence: 99%

“…5 For these syntheses, it has been reported that the presence of some hydroquinone or DDQ is required to stabilize the produced 2-hydroxyethyl thiocyanates and to inhibit its conversion to thiirane. 6,7 Although reagents such as Ti(O i Pr) 4 , 8 Ph 3 P(SCN) 2 , 9 TiCl 3 (or ZnCl 2 ), 10 Pd(PPh 3 ) 4 , 11 TMSNCS (Cat. TBAF) 12 and PTC 13 are useful, they are limited to specific oxiranes and are not applicable as versatile reagents in the preparation of 2-hydroxyethyl thiocyanates.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Metalloporphyrins as new catalysts in the mild, efficient and regioselective conversion of epoxides to β-hydroxy thiocyanates with NH₄SCN

2004

View full text Add to dashboard Cite

show abstract

DDQ CATALYSES THE CONVERSION OF EPOXIDES TO ß-HYDROXY THIOCYANATES WITH NH₄SCN

Cited by 27 publications

References 13 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

Metalloporphyrins as new catalysts in the mild, efficient and regioselective conversion of epoxides to β-hydroxy thiocyanates with NH₄SCN

Contact Info

Product

Resources

About

DDQ CATALYSES THE CONVERSION OF EPOXIDES TO ß-HYDROXY THIOCYANATES WITH NH4SCN

Cited by 27 publications

References 13 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

Metalloporphyrins as new catalysts in the mild, efficient and regioselective conversion of epoxides to β-hydroxy thiocyanates with NH4SCN

Contact Info

Product

Resources

About

DDQ CATALYSES THE CONVERSION OF EPOXIDES TO ß-HYDROXY THIOCYANATES WITH NH₄SCN

Metalloporphyrins as new catalysts in the mild, efficient and regioselective conversion of epoxides to β-hydroxy thiocyanates with NH₄SCN