Trans-cyanation

TALALAY, P., ZHANG, Y., Chemoprotection against cancer by isothio-cyanates and glucosinolates, Biochem. Soc. Trans., 1996, 24, 806-810. 

In addition, stereoselective synthesis of solenopsin A has been reported by four research groups. An approach utilizing the stereoselective reductive de-cyanation (596) starts with aminonitrile 229, prepared from 2-picoline. It was selectively hydrogenated in the presence of Pd-C, followed by alkylation with undecyl bromide, affording 231. Reductive decyanation of 231 with NaBH4 in MeOH led to predominant (8 2) formation of the trans isomer (232) which was then debenzylated to ( )-solenopsin A (Id). The cis product (Ic) was in turn prepared by treatment of 231 with sodium in liquid ammonia followed by de-benzylation (Scheme 10). 

Cyanogen Iodide (ICN) has been used extensively for the cyanation of alkenes and aromatic compounds [12], iodination of aromatic compounds [13], formation of disulfide bonds in peptides [14], conversion of dithioacetals to cyanothioacetals [15], formation of trans-olefins from dialkylvinylboranes [16], lactonization of alkene esters [17], formation of guanidines [18], lactamization [19], formation of a-thioethter nitriles [20], iodocyanation of alkenes [21], conversion of alkynes to alkyl-iodo alkenes [22], cyanation/iodination of P-diketones [23], and formation of alkynyl iodides [24]. The products obtained from the reaction of ICN with MFA in refluxing chloroform were rrans-16-iodo-17-cyanomarcfortine A (14)... 

Cyanation Catalyzed by trans-CHLORO ( aryl ) bis ( triphenylphos-phine) nickel (II) Complexes. In Table III cyanation of aryl halides catalyzed by the Ni(II) complexes obtained by reaction between aryl halides and Ni[P(C6H5)3]3 (Reaction 2) is shown. In general the trans-chloro (1-naphthyl) bis (triphenylphosphine) nickel (II) complex was used. Ortho substituted aryl halides were allowed to react in dimethylformamide... 

The reactions were carried out by using trans-chloro( 1-naphthyl)-bis(triphenylphosphine)nickel(II) (l, Ar = Ci0H7) complex as catalyst in the presence of various phosphorus ligands. We observed that aromatic phosphines in arylnickel(II) complexes 1 are easily replaced by aliphatic phosphines. In fact in the presence of alkylphosphines, such as P( C6Hn )3 and P(C4H9)3, cyanation did not occur. Moreover phosphites such as... 

Table IX. Cyanation of trans-Chloro(aryl)bis(triphenylphosphine)-nickel(II) Complexes, IR Absorptions...

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... 

Y. Ichikawa, M. Osada, I. I. Ohtani, and M. Isobe, A new synthetic method for the preparation of amino sugars through an allyl cyanate-to-isocyanate rearrangement, J. Chem. Soc., Perkin Trans. 1, (1997) 1449-1455. 

The structure of Co(acac)3 is a distorted octahedron, Co—O = 1.888(4) A, Z OCoO = 96.5°.355 Thermal decomposition of Co(acac)3 to Co(acac)2 has been reported, and the mass spectra of Co(acac)2,oxine and Co(acac)(oxine)2 have been studied.356 Acetic acid and [Co(CO)3L2]+ (L = bipy or phen) in alcohol-water react to form [Co(acac)L2]2+ and [Co(acac)2L] +. 357 The cis-trans isomerization of [Co(acac)2(py)X] (X = N3, N02, NCO, or CN) has been examined and the trans - cis rate is N3 > NCO > N02 > CN.358 Potassium cyanate reacts with Co(acac)2 in aqueous solution in the presence of pyridine and hydrogen peroxide to form [Co-(acac)2(NCOXpy)].358 An extension of this work to KNCS produced trans-[Co(acac)2-(SCN)(py)]. On standing this complex undergoes linkage isomerism to the isothio-cyanato analogue, whilst under reflux cis-[Co(acac)2(NCSXpy)] forms.359... 

More complex, but still feasible, is the synthesis of pyrimidine bases from simple prebiotic substrates, although the reported yields of these reactions are relatively low. In this context, two main prebiotic precursors have been identified cyanoethine and a primary product of its hydrolysis, cyanoacetaldehyde. These compounds contain a preformed C-C bond which is incorporated in the C5-C6 position of the pyrimidine ring. In 1968 Ferris and co-workers reported that the reaction of cyanoethine with cyanate at 30 °C yields cytosine and, after its hydrolysis, uracil in acceptable yield [27]. trans-Cyanovinylurea was recovered as a key intermediate for this transformation. However, this reaction requires relatively high concentrations of cyanate (>0.1 mol/1), unlikely to occur in aqueous media due to its rapid degradation to carbon dioxide and ammonia. Cyanoethine also reacts with cyanate and yields cytosine and uracil at elevated temperatures. In this reaction urea or guanidine (also considered as prebiotic organic compounds) can easily replace cyanate (Figure 8.8) [26]. 

Halomercaptans are converted to thietanes by treatment with a as exemplified by the formation of 3-hydroxythietane 21 from 3-chloro-l-mercapto-2-propanol 20 4-thiocyano-2-pentanol 22 is converted to a mixture of cis- and trans-2,4-dimethylthietane 23 by treatment with sodium hydride. The latter reaction involves displacement of cyanate ion by the mercaptide ion. 2,2,4-Trimethylthietane was also prepared by this method. 

In contrast to that, nucleophilic substitution in a-position to nitrogen by cyanide or methoxide predominates, if the electrolysis is carried out in acetonitrile or methanol in presence of cyanide [49], respectively, in basic methanol [50,51]. This reaction, which is supposed to occur via the iminium ion, is interesting for application in organic synthesis. The formation of synthetically valuable o -aminonitriles from 7V,7V-dialkylani-lines has been reported by Andreades and Zahnow [49]. More recently, a series of papers was published by Hurvois, Moinet, Tallec, et al. on the anodic a-cyanation of A-sub-stituted 1-benzazepines, tetrahydroquinolines, and piperidines [Eq. (9)] [52]. The reactions were performed in a special flow-through cell. In the case of the 3-methyl-substituted benzazepines the reaction is stereospecific, leading only to the trans-a-cyano diastereomer. 

Hanson, P., Rowell, S. C., Taylor, A. B., Walton, P. H., Timms, A. W. Sandmeyer reactions. Part 6.1 A mechanistic investigation into the reduction and ligand transfer steps of Sandmeyer cyanation. J. Chem. Soc., Perkin Trans. 2 2002, 1126-1134. 

Iodine isocyanate, IN=C=0. Mol. wt. 168.93. Preparation from silver cyanate and iodine. The reagent adds to olefins in the trans manner to give iodo-isocyanates," of interest because they can be transformed into ethyleneimines." The reaction is... 

Sato, N., Shimomura, Y., Ohwaki, Y., and Takeuchi, R., Studies on pyrazines. Part 22. Lewis acid-mediated cyanation of pyrazine A-oxides with trimethylsilyl cyanide. New route to 2-substituted 3-cyanopyrazines, J. Chem. Soc., Perkin Trans. 1, 2877, 1991. 

Stereospecific conjugate cyanation. By adjusting the reaction conditions, Kelly et al. were able to convert the octalone (1) into either the cis-cyano-decalone (2) or the trans-isomer (3). 

Ethoxybenzene 2-Ethoxyethanol 2-Ethoxyethyl acetate Ethyl acetate Ethyl acrylate Ethylamine gauche) Ethylamine trans) Ethylamine average) Ethylbenzene Ethyl benzoate Ethyl butanoate Ethyl ra 5-cinnamate Ethyl cyanate Ethyl cyanoacetate Ethylene carbonate Ethylene glycol average) Ethyleneimine Ethylene-sulfur dioxide complex... 

C3H5NO Ethyl cyanate 4.72 0.09 C3H8S Ethyl methyl sulfide (trans) 1.56 0.03... 

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