Thiocyanates, alkenes with reaction

A series of papers detailing a continuation of the study of the synthesis and reactions of uic-iodothiocyanates and -iodoisothiocyanates has been published.Similarly, the treatment of alkenes with thiocyanogen bromide [from equimolar quantitites of bromine and thallium(i) thiocyanate] gives moder-ate-to-high yields of uic-bromothiocyanates. " Unlike the analogous vic-iodothiocyanates, the bromo-compounds are not readily isomerized to the corresponding isothiocyanates. 

Type B Syntheses (C—C—N + C—S).—Thiocyanation of oi -unsaturated jS-amino-ketones R3HNCRi=CHC(0)R2 (Ri = Me or Ph R= = Me, Ph, or OEt R = H, Me, or Ph) with cyanogen occurs at the olefinic H-atom, or gives a 2-imino-A -thiazoline, or its rearranged isomer (8), depending upon the structure of the starting material and reaction temperature. The thiocyanated alkenes are cyclized to mixtures of the cyclized products in acid or alkali, or else thermally. 

A single report of the addition of sodium azide to cyclohexene in the presence of iodine under phase-transfer catalytic conditions to produce 2-iodocyclohexanyl azide has the potential for extension to other alkenes [17], The analogous reaction of cyclohexene with potassium thiocyanate and iodine produces 2-iodocyclohexyl isothiocyanate (17%) and 2-iodocyclohexanyl thiocyanate (61%). Similar products are obtained with other alkenes [17],... 

A number of sulfur-centered radical scavengers have been employed for Meerwein type carbothiolation reactions [109, 110]. The most prominent of those are certainly xanthates [111-113] and thiocyanates, among which the latter have received special attention recently. As shown in Scheme 21, thiocyanates are well-suited for the functionalization of activated and non-activated alkenes [114, 115]. Remarkably, the reaction of 56 with 2-methallyl chloride to give 57 is not significantly impeded by the possible (3-fragmentation of a chlorine radical, which would lead to allylation products [116]. With an activated and a non-activated alkene present in a substrate... 

Iron(n) salts mediated the coupling of trialkylboranes with KSGN to give RSCN via a radical process.553,554 Stereochemically pure ( )-l-thiocyanato-alkenes or ( )-l-azide-alkenes were obtained from alkynes when hydro-boration with disiamylborane was followed by reaction with potassium thiocyanate or sodium azide in the presence of copper(n) nitrate, copper(n) acetate, and small amount of water in polar aprotic solvent (Equation (116)).555... 

The full paper on the reactions of iodine(l) thiocyanate and 5a-androst-2-ene and other alkenes has appeared." An investigation into the stereochemistry of the addition of BrCl to cholesterol revealed that the ratio of a /8 attack was 4.5 1, which was higher than that for other electrophilic additions. It was suggested that the reaction involved rapid reversible formation of the bromonium ions followed by attack by chloride ion and that the opening of the 5/8,6/3-bromonium ion was slow relative to that of the 5a,6a-bromonium ion owing to steric interactions with the la-, 3a-, 7a-, and 9a-axial hydrogen atoms. 

The regioselective amination of 2,3-dihydrofuran with morpholine catalyzed by palladium thiocyanate diphosphine complexes (45 turnovers)102, and the regioselective addition of aniline to acrylonitrile and analogous electron-poor alkenes catalyzed by dialkylpalladium(dmpe) complexes (hundreds of turnovers)103 have recently been reported, but the scope of the reactions is limited to the specific type of alkene. 

Episulfides. Hinshaw reasoned that addition of an alkene to such solutions should give jS-iodothiocyanates in analogy with the reaction of iodine isocyanate (1, 501 2, 223-224 . 3, 161 -16.3) with alkenes. indeed treatment of cyclohexene with iodine thiocyanate gives a /5-iodothiocyanate (2), which on treatment with methanolic... 

Treatment of oc-halo ketones 1392 (X = Br, Cl) with potassium thiocyanate and monosubstituted hydrazines 1393 provides Ar-aminoimidazoline-2-thiones [1397, R R = Me, Ph R R = (042)4 R = Ph, 4-O2NC6H4, PhCH2, etc.]. The reaction is considered to proceed via the formation of azo-alkenes 1394 and thiocyanic acid 1395. The intermediates, in turn, undergo a [34-2] cycloaddition reaction to give azomethine imine cycloadducts 1396, which proceed to the final products 1397 (Scheme 361) <199714(45)691, 2003JME1546>. 

Thiiranes can be prepared directly from alkenes using specialized reagents. Thiourea with a tin catalyst gives the thiirane, for example. " Interestingly, internal alkynes were converted to 1,2-dichorothiiranes by reaction with S2CI2 (sulfur monochloride).It is noted that epoxides are converted to thiiranes with ammonium thiocyanate and a cerium complex. " A trans-thiiration reaction occurs with a molybdenum catalyst, in which an alkene reacts with styrene thiirane to give the new thiirane. 

Although the reaction of 1,2-dichloro-3,3-difluorocyclopropene with thiocyanate leads simply to the replacement of the two chlorines by the nucleophile, reaction of the cyclopropene or of tetrachlorocyclopropene with sodium arylsulfinates gave an alkene in low yield (< 10%), apparently via the cyclopropenone, e.g. reaction of I. ... 

SELENIC ANHYDRIDE (13768-86-0) OgSe Noncombustible solid. Violent reaction with water, forming selenic acid. A strong oxidizer. Violent reaction with many substances including reducing agents, hydrides, nitrides, and sulfides cyanides, esters, combustible materials, active metals, organic substances, aldehydes, alkenes, carboxylic acids, isocyanates, and thiocyanates. Attacks most metals in the presence of moisture. 

Saturated hydrocarbons are dehydrogenated when heated with sulfur, and further reaction with alkenes occurs. An application of this reaction is in the vulcanization of rubber, in which soft rubber is toughened by cross-linking of the poly-isoprene chains, making it suitable for use in, for example, t)Tes. The reactions of sulfur with CO or [CN] )deld OCS (16.13) or the thiocyanate ion (16.14), while treatment with sulfites gives thiosulfates (equation 16.21). 

Acetates of MBH adducts have also been established for the synthesis of sulfur-containing trisubstituted alkenes via a nucleophilic displacement protocol, in either S- 2 or S- 2 fashion with 5-centered nucleophiles, such as thio-lates, ° arenesulfinate and thiocyanate anions. Significantly, these reactions are highly stereoselective for both acrylonitrile/acrylate ester-derived MBH acetates, but with a reversed stereochemical directive effect, that is, acrylonitrile-derived MBH acetates afford ( )-sulfur-containing trisubstituted alkenes 336 as the sole product, while acrylate ester-derived MBH acetates afford (Z)-olefins 335 exclusively under the same reaction conditions. Both (Z)-and ( )-allyl sulfides have been stereoselectively obtained from MBH acetates in a one-pot with treatment with benzenethiol in the presence of catalytic amounts of 15% aqueous NaOH and TBAI in DM SO at room temperature (Scheme 3.146). ° The method has also been applied for the synthesis of (Z)-3-(4-methoxybenzylidene)thiochroman-4-one (337), a potent antifungal compound (Scheme 3.147). 

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