Nitriles heterocycles from

Further examples of intramolecular 1,3-dipolar cycloadditions (cf. Section 10.21.9.2.2(ii)) include the synthesis of an isoxazolidine from nitrone 193 (Equation 128) <1997J(P1)1805>, and a pyrazolo heterocycle from the nitrile oxide generated in situ from the oxime 194 (Equation 129) <1999TL3535>. 

Names, P., Balazs, B., Toth, G., Scheiber, P. Synthesis effused heterocycles from 3-enamino nitrile and carbonyl compounds. Synlett... 

That nitriles derived from propargyl alcohols are versatile substrates in Hne organic chemistry has already been mentioned. The actual richness of this chemistry may be deduced from Scheme 2-1, which has been adapted from a recent review article [35]. Whether four-, five- or six-membered, polyfunctional heterocycles all are readily obtained from 29-derived starting materials.. 

Nitrile molecules from 4-amino-l,2,4- Deamination of N-amino-N-triazoles. 4-Amino-3,5-diphenyl-l,2,4-tri- heterocyclics. N-Aminocarbazole azole... 

K. Gewald, E. Schinke, H. Bottcher, Chem. Ber. 1966, 99, 94-100. 2-Amino-thiophene aus methylenaktiven nitrilen carbonylverbindungen und schwefel. (Heterocycles from C-H acidic nitriles VIII. 2-Aminothiophenes from methylene active nitriles, carbonyl compounds, and sulfur). 

Yin W, Wang C, Huang Y (2013) Highly practical synthesis of nitriles and heterocycles from alcohols under mild conditions by aerobic double dehydrogenative catalysis. Org Lett 15(8) 1850-1853... 

Synthesis of Substituted Heterocycles Transition-metal-mediated or transition-metal-catalyzed co-cycloaddition of two alkynes and one nitrile is one of the simplest synthetic pathways to construct pyridine framework. However, there is a critical problem in selectivity in the intermolecular coupling of two different alkynes and a nitrile resulting from the reaction mechanism via metalacyclopentadi-ene [17]. For example, in Co-mediated pyridine formation, cobaltacyclopentadiene 37 was first prepared from two different alkynes by sequential addition because aza-cobaltacyclopentadiene could not be formed via selective coupling of one alkyne and a nitrile. A mixture of two pyridine regioisomers was obtained in the final step due to the existence of two possible orientations of the nitrile toward cobaltacyclopentadiene intermediate 37 [Scheme 11.15, Eq. (1)] [17b,c]. To control the... 

Magnesium perchlorate/p-toluenesulfonic acid Ring expansion by insertion of nitriles 5- from 3-Membered heterocyclics... 

As a class of compounds, nitriles have broad commercial utility that includes their use as solvents, feedstocks, pharmaceuticals, catalysts, and pesticides. The versatile reactivity of organonitnles arises both from the reactivity of the C=N bond, and from the abiHty of the cyano substituent to activate adjacent bonds, especially C—H bonds. Nitriles can be used to prepare amines, amides, amidines, carboxyHc acids and esters, aldehydes, ketones, large-ring cycHc ketones, imines, heterocycles, orthoesters, and other compounds. Some of the more common transformations involve hydrolysis or alcoholysis to produce amides, acids and esters, and hydrogenation to produce amines, which are intermediates for the production of polyurethanes and polyamides. An extensive review on hydrogenation of nitriles has been recendy pubHshed (10). 

In theory, three isoxazolines are capable of existence 2-isoxazoline (2), 3-isoxazoline and 4-isoxazoline. The position of the double bond may also be designated by the use of the prefix A with an appropriate numerical superscript. Of these only the 2-isoxazolines have been investigated in any detail. The preparation of the first isoxazoline, 3,5-diphenyl-2-isoxazoline, from the reaction of )3-chloro-)3-phenylpropiophenone with hydroxylamine was reported in 1895 (1895CB957). Two major syntheses of 2-isoxazolines are the cycloaddition of nitrile A-oxides to alkenes and the reaction of a,/3-unsaturated ketones with hydroxylamine. Since 2-isoxazolines are readily oxidized to isoxazoles and possess some of the unique properties of isoxazoles, they also serve as key intermediates for the synthesis of other heterocycles and natural products. 

The ketoxime derivatives, required as starting materials, can be prepared from the appropriate aromatic, aliphatic or heterocyclic ketone. Aldoximes (where R is H) do not undergo the rearrangement reaction, but rather an elimination of toluenesulfonic acid to yield a nitrile. With ketoxime tosylates a Beckmann rearrangement may be observed as a side-reaction. 

Similar cycloadditions between thiirene dioxides and 1,3-dipoles generated in situ give heterocycles which result from either loss of sulfur dioxide or from the three-membered ring opening of the initially formed adduct (e.g. 174). Such cycloadditions with nitrilium imides (173a) and nitrile ylids (173b) are illustrated in equation 69175. 

AT-heterocyclic carbenes show a pure donor nature. Comparing them to other monodentate ligands such as phosphines and amines on several metal-carbonyl complexes showed the significantly increased donor capacity relative to phosphines, even to trialkylphosphines, while the 7r-acceptor capability of the NHCs is in the order of those of nitriles and pyridine [29]. This was used to synthesize the metathesis catalysts discussed in the next section. Experimental evidence comes from the fact that it has been shown for several metals that an exchange of phosphines versus NHCs proceeds rapidly and without the need of an excess quantity of the NHC. X-ray structures of the NHC complexes show exceptionally long metal-carbon bonds indicating a different type of bond compared to the Schrock-type carbene double bond. As a result, the reactivity of these NHC complexes is also unique. They are relatively resistant towards an attack by nucleophiles and electrophiles at the divalent carbon atom. 

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