Isonitriles isocyanates

As with the aryl compounds the reaction scheme is simplified for the sake of clarity. The reactions observed are various and include reductive coupling (ketones, nitriles), insertion (diphenylacetylene, isocyanate, isonitrile, CO2 and CO), and disproportionation (diphenylacetylene, CS2). The course of the reactions and the complexity of the product mixtures strongly depend on the nature of the alkyl groups and the substituents on the substrate molecule. As examples we will discuss reactions with ketones, acetylenes and CO. The reaction with ketones strongly resembles the coupling of nitriles R C=N on Cp2TiR (R = aryl). The coupling proceeds more slowly when R, R and R" increase in size. 

Note that carbon monoxide inserts into the Zr-H bond of 1 (2 equiv.) to afford an T -formaldehydo-type complex [(Cp2ZrCl)]2(g-CH20) [200-202]. Iminoacyl zir-conocene complexes are formed after addition of 1 to isonitriles [203]. Carbon dioxide [183, 202] is reduced to formaldehyde with 1 (2 equiv.). C02-like molecules such as isocyanates RNCO [204], isothiocyanates RNCS [205], and carbodiimides RNCNR [204] are readily converted to the corresponding bidentate form-amido ligands. 

More recently, Belzner et al. reported a new type of oxygen transfer reaction from isocyanates to bis[2-(dimethylaminomethyl)phenyl]silylene (8)18 which was thermally generated from the corresponding cyclotrisilane 7, and they obtained some convincing results of the involvement of silanone 9 (Scheme 3). However, they found that silanone 9 is not stable enough to be isolated. Only cyclic di- and trisiloxanes 10 and 11 (i.e., the cyclic dimer and trimer of the silanone 9) were obtained together with the corresponding isonitrile as other main products when... 

Cp Sm 59 (it can be regarded as a vinylsamarium when a Cp coordinates Sm in an -fashion) is an extremely crowded molecule, which displays high reactivity with substrates including CO, nitriles, isonitriles and isocyanates.31 The reactions proceed according to Scheme 20. 

Isonitrile insertion into zirconacycles to afford iminoacyl complexes 28 is fast, but rearrangement to q2-imine complexes 30 is slow. In the case of tBuNC, the rearrangement does not occur. Amines 32 are formed on protonolysis of the q2-imine complex. The q2-imine complexes 30 readily undergo insertion of Ti-components (alkenes, alkynes, ketones, aldehydes, imines, isocyanates) to provide a wide variety of products 37 via zirconacycles 36. The overall sequence gives a nice demonstration of how a number of compo-... 

Isonitrile complexes, having a similar electronic structure to carbonyl complexes, can also react with nucleophiles. Amino-substituted carbene complexes can be prepared in this way (Figure 2.6) [109-112]. Complexes of acceptor-substituted isonitriles can undergo 1,3-dipolar cycloaddition reactions with aldehydes, electron-poor olefins [113], isocyanates [114,115], carbon disulfide [115], etc., to yield heterocycloalkylidene complexes (Figure 2.6). 

Koenig GM, Wright AD, Angerhofer CK. (1996) Novel potent antimalarial diterpene isocyanates, isothiocyanates, and isonitrile from tropical marine sponge Cymbastela hooperi. J Org Chem 61 3259-3267. 

Upon reaction of A -vinyliminophosphoranes (109) with aromatic isocyanates, vinylcarbodiimides (110) are formed, as shown in Scheme 47. Divi-nylcarbodiimides (111) can be obtained as side products (88CB271). With isonitriles the vinylcarbodiimides also afford pyrroles (112) via [4 + 1]-cycloaddition. Divinylcarbodiimide can also react via [4 -l- l]-cycloaddition with an isonitrile, whereupon an electrocyclic step of the initial diaza-1,3,5-trienes (113) follows. Finally, the pyrrolo[2,3-e]pyrazine 114 is obtained (88CB271). 

The following are some examples of reactions which have produced vinylidene complexes but are either not of general application or have not been further developed. Oxygen atom transfer occurs in reactions of NbH (t] — OC — CPh2) Cp 2 with nitriles or isonitriles to give isocyanates and Nb(=C=CPh2)Cp 2 [260]. Metathesis of Ph(R) C=C=NPh (R = Me, aryl) with W(=CHPh)(CO)5 proceeds via W C(NPh=CHPh)=C (R)Ph (CO)s, which is converted to W =C=C(R)Ph (CO)5 by treatment with BF3. OMe2 [261]. 

When a toluene solution of a mixture of cyclotrisilane 34 and cyclohexyl isocyanate (or f-butyl isocyante) was heated at 70 °C, cyclic di- and trisiloxanes 37 and 38, i.e. the cyclic dimer and trimer of the silanone 36, were obtained together with the corresponding isonitrile RN=C. The formation of 37 as well as 38 was completely suppressed in the presence of hexamethylcyclotrisiloxane (19 D3) instead, quantitative conversion of 35 into 39, the formal insertion product of the silanone 36 into the Si—O bond of D3, occurred (Scheme 14). Since neither cyclodisiloxane 37 nor cyclotrisiloxane 38 reacted with D3 under the reaction conditions, the possibility that 37 or 38 is the precursor of 39 was ruled out. Whereas the oxidation of 35 with cyclohexyl and t-butyl isocyanates proceeded with exclusive formation of 37 and 38 (as the silicon-containing compounds) the reaction of 35 with phenyl isocyanate resulted in the formation of 37 in low yield. Furthermore, in this case the presence of D3 did not totally suppress the formation of 37. According to the authors, these results indicate that the oxidation of 35 with cyclohexyl and f-butyl isocyanates appears to use other reaction channels than that with phenyl isocyanate. 

According to Scheme 4 elimination of a proton from the iminodiazonium ion (I) forms the nitrile. Rearrangement of the ion (I) leads to formanilide. But there are no data available supporting these ideas. Another possible way for the formation of nitrile is a rearrangement of the iminocarbonium ion (II) of the type which occurs in the isomerization of isonitriles to nitriles". It was found that in 71.2-90.4% sulphuric acid, phenyl isocyanate is converted quantitatively into formanilide. For a better understanding of the... 

Imidate salts hydrolysis, 118-144 syn and anti, 120 isomerization, 142 B-lactam, 142 Iminium salts, 211-221 Imino-ethers, 147 lodolactonization, 169 Ionic state of tetrahedral intermediates, 65, 105-106, 119 Ionophore A-23187, 13 Isochromane-3-one, 70 Isocyanate, 300 Isonitrile, 296... 

The retrosynthetic approach to welwitindolinone A isonitrile (6) used by the Wood group is shown in Scheme 33. After recognition of the possibility of deriving the vinyl isonitrile fragment from a ketone, the disconnection of 6 to 140 was proposed. A literature report of a samarium (II) iodide-mediated reductive coupling of acrylates with isocyanates to give amides, which could be expected to lead to a new spirooxindole synthesis, prompted the disconnection of 140 to 141. This compound was to be obtained from the readily available cyclohexadiene derivative 143, by way of bicyclic ketone 142. 

Under VI we find that hydrogen chloride does add reversibly and stoichiometrically to hydrocyanic acid, but not to give pentavalent nitrogen. It forms amino-formyl chloride, H2C(C1) NH. This substance would undoubtedly add hydrogen chloride to the nitrogen if it did not polymerize. The polymerization products of the nitriles, isonitriles, cyanates and isocyanates have not been studied with any satisfactory degree of care. 

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