Nitriles fragmentation

Fluorinated 1,2,5-oxadiazoles 255 (Equation 52) undergo photolytic loss of a nitrile fragment and reaction with a nucleophile to give the fluorinated 1,2,4-oxadiazoles 256 <2000TL7977, 2001T5865, 2004JFC165>. 

Substituted oxazoles heated with DMAD in toluene in the presence of hydroquinone gave474 the furans 12 in up to 90% yield. Dimethyl acetylenedicarboxylate reacts similarly with other oxazoles,476 whereas MP gives mixtures of the possible isomeric furans.476 Addition of DMAD to the oxazole 13 in boiling ether gave 14 with retention of the nitrile fragment.474... 

An interaction of compounds 74 with nitriles can proceed both in an intra- <1996J(P1)225> and intermolecular <1984CHEC(6)897> manner. If the exocyclic imine group in compound 74 is linked with the nitrile fragment through a three-, four-, or five-atom tether, 5/5, 5/6, and 5/7 fused 1,2,4-thiadiazoles 76-78 are formed <1996J(P1)225>. 

Other products that form from the pyrolysis of amino acids are aldehydes, which contain one less carbon atom than the parent amino acid. This process occurs via an SNi deamination mechanism. Another process that can occur is side chain stripping involving chain homolysis. The result is the production of various saturated and unsaturated compounds. Many alpha-amino acids, when pyrolyzed, form an amine fragment, a nitrile fragment, and aldehydes that contain one less carbon atom than the parent amino acid. Also, a side stripping mechanism can result in various saturated and unsaturated compounds. ... 

The successful completion of the pederin synthesis gave us the appropriate level of confidence to apply the method to the synthesis of psymberin (Scheme 13)." We were unable to effect a cyanation reaction of diol 25 under the conditions that were effective in the pederin synthesis, forcing us to activate the hydroxyl group prior to ionization. Concerns about the compatibility of an acetate group in the nitrile fragment from our original approach led us to... 

The Beckmann rearrangement reaction provides a number of examples of fragmentation. The products that result from fragmentation are a carbonium ion and a nitrile. Fragmentation is very likely to occur if X is a nitrogen, oxygen, or... 

The most important chemistry of azidoazoles is the fragmentation of derived nitrenes of which the prototypes are (453) (454) and (455) (456). Thus 5-azido-l,4-diphenyltriazole (457) evolves nitrogen at 50 °C (70JOC2215). 4-Azido-pyrazoles and -1,2,3-triazoles (458) undergo fragmentation with formation of unsaturated nitriles (8lAHC(28)23l). 

Thermolysis of 4- and 5-azidopyrazoles has been studied by Smith (B-70MI40402, 81AHC(28)232). These compounds undergo fragmentation with formation of unsaturated nitriles via the nitrenes (474a) and (474b Scheme 42). 

The thermal or photolytic fragmentation of furazans to nitriles and nitrile Af-oxides has been reported (73JOC1054, 75JOC2880). The irradiation of dimethylfurazan (419) in the presence of cyclopentene, and benzofurazan (420) in the presence of dimethyl acety-lenedicarboxylate, gave isoxazoline (421) and isoxazole (422), respectively, in good yields. The thermolysis of acenaphtho[l,2-c]furazan (423) in the presence of phenylacetylene gave isoxazole (424) in 55% yield. 

Perhaps the most firmly based report for the formation of an azete involves flash pyrolysis of tris(dimethylamino)triazine (303). This gave a red pyrolysate believed to contain the highly stabilized azete (304) on the basis of spectroscopic data. The putative azete decomposed only slowly at room temperature, but all attempts to trap it failed (73AG(E)847). Flash pyrolysis of other 1,2,3-triazines gives only acetylenes and nitriles and it is not possible to tell whether these are formed by direct <,2-l-<,2-l-<,2 fragmentation of the triazine or by prior extrusion of nitrogen and collapse to an azete (81JCR(S)162). 

The type of the thermolysis process depends on the nature of the acyl group. Thus, other types of thermolysis processes involve reversible fragmentation of the furoxan ring to give two molecules of the corresponding nitrile oxide followed... 

Syntheses in which a nitrile provides atoms 1 and 2 start from an ylide (82JFC373), or a 1-amino-2-pyridone (82S974) to give compounds 45 and 46. Other two atom fragments used with l-amino-2-pyridones are amides which give compounds such as 47 (86S860). 

A thiazole derivative that incorporates a fragment of the amphetamine molecule shows some CNS stimulant activity more specifically, the compound antagonizes the depression caused by overdoses of barbiturates and narcotics. Reaction of benzalde-hyde with sodium cyanide and benzenesulfonyl chloride gives the toluenesulfony1 ester of the cyanohydrin (141). Reaction of this with thiourea leads directly to aminophenazole (143) It is probable the reaction proceeds by displacement of the tosylate by the thiourea sulfur to give 142 addition of the amino group to the nitrile followed by tautomerization affords the observed product. ... 

Fragmentation The saturated aliphatic mononitriles with molecular weights greater than 69 are characterized by intense ions at m/z 41, 54, 68, 82, 96, 110, 124, 138, 152, 166, and so forth. Aliphatic nitriles undergo the McLafferty rearrangement producing the m/z 41 ion. 

Certain ketoximes can be converted to nitriles by the action of proton or Lewis acids. Among these are oximes of a-diketones (illustrated above), a-keto acids, a-dialkylamino ketones, a-hydroxy ketones, p-keto ethers, and similar compounds. These are fragmentation reactions, analogous to 17-25 and 17-26. For example, ot-dialkylamino ketoximes also give amines and aldehydes or ketones besides nitriles. 

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