Thiocyanates, alkenes with

Scheme 21 Carbothiolation of non-activated and activated alkenes with thiocyanates [92, 114, 115]...

Thiourea or potassium or ammonium thiocyanates react with alkene oxides at room temperature in aqueous solution to give cyclic sulfides in 50-73% yields. ... 

The conversion of oxirans into thiirans by the action of sulphur nucleophiles has been further exploited, using thiourea or a thiocyanate. " Treatment of alkenes with (3) or (4), followed by reduction with L1A1H4, gives thiirans in good yields in a process that provides an alternative method for the conversion of alkenes into episulphides. Vicinal iodo-thiocyanates are converted into thiirans when treated with base. ... 

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],... 

Crystal structures of the benzotriazole complexes [Zn(HL)Cl2] and [Zn2L4] (HL = benzotriazole 62) have been reported the former compound has the metal in a tetrahedral N2C12 environment (Zn—N, 2.014, 2.034 A Zn—Cl, 2.241, 2.235 A) and the latter is a polymeric species.441 The complex [H2L]2[ZnCU] (HL = 62) has also been described it is isostructural with the tetrachlorocobaltate(II) analogue, which has previously been structurally characterized.441 The synthesis and powder diffraction pattern for [ZnL Cy (L = 62) have also been reported.442 Complexes of the type MX2L2 (M - Zn, X = Cl, Br, I or SCN M = Cd, X = Cl L = allyl or 3,5-dimethylpyrazole) have been synthesized where L is 3,5-dimethylpyrazole, cadmium also forms the complexes (CdBr2L3 and CdI2L4. When L is allylpyrazole, alkene coordination is not observed thiocyanate is N-bonded.443,444... 

The addition of olefinic compounds to the three component system, BAIB/TMSNCS/PhSeSePh (2.5 1 5), or its KSCN variant, results in stereo- and regioselective (trans, Markovnikov) phenylselenenyl-thiocyanation (or -isothio-cyanation) of the C,C-double bond (Scheme 13) [36]. Whether C-S or C-N bond formation occurs when the SCN group is introduced seems to depend on the capacity of the alkene to stabilize carbocation-like intermediates. For example, C-S bond formation occurred with cyclohexene, while C-N bond formation... 

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. 

Other sulfenyl derivatives undergo addition to alkenes in a rraws -stereoselective manner. For example, 2,4-dinitrobenzenesulfenyl thiocyanate, on treatment with (Z)- or ( )-2-butene, affords the 1 1 adducts 816a 2,4-dinitrobenzenesulfenyl acetate reacts with cyclohexene to give tram-91 sb. 

Phenylseleno thiocyanate rapidly undergoes addition to alkenes without the presence of a catalyst, producing -thiocyanates and/or /1-isothiocyanates. The stereoselectivity of the addition is less predictable than with other selenenyl electrophiles. 

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. 

In contrast, the photolysis of these azides at 350 nm leads only to the corresponding nitriles and olefins in yields of 90 l-(Alkylthio)cyclopropyl azides (164), readily accessible from the corresponding chlorides and bromides, are smoothly decomposed at ITC with nitrogen evolution. The main process is a ring enlargement to 2-(alkylthio)azetines (165), accompanied by cleavage to an alkyl thiocyanate and an alkene (equation 114). ... 

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