Nitrile From alkyne

Dutta U, Lupton DW, Maiti D (2016) Aryl nitriles from alkynes using tert-butyl nitrite metal-liee approach to C=C bond cleavage. Oig Lett 18(4) 860-863... 

In the context of pyridin synthesis from alkynes and nitriles homogeneously catalyzed by (cyclopentadienyl)cobalt complexes (Eq. 13), it was found that electron-withdrawing groups on the cyclopentadienyl ring significantly increase the activity [63]. During the screening of various cobalt half-sandwich complexes... 

Scheme 10.17 Nitriles from addition of hydrazine to terminal alkynes.

Much recent work has been done on the synthesis of pyridines from alkynes and nitriles over cobalt catalysts. For example, 2-vtnylpyndine has heen obtained in good yield from acetylene and acrylonitrile using a cyclopentadienyl-cobalt catalyst. Pyridine has also been obtained from cyclopentadiene and ammonia over a sihca/alumina catalyst. 

The reactions between sydnones (e.g. 26) and unsaturated compounds frequently yield pyrazoles. Pyrazolines are produced by 1,3-dipolar addition to alkenes, and pyrazoles from alkynes.372-374 The cyanopyrazolines formed from a,/3-unsaturated nitriles are immediately converted to pyrazoles.373... 

An important and extensively investigated application of CpCo complex chemistry is the catalyzed synthesis of pyridines from alkynes and nitriles. Dissociation of the L ligands liberates the CpCo fragment to react with alkyne to form a cobaltacyclopentadiene complex. The nitrile coordinates to this intermediate and subsequently undergoes insertion to form a seven-membered cobaltacycle. Reductive coupling gives pyridine and reforms CpCo. Asymmetric alkynes add to the carbon with the bulkier substituent adjacent to the nitrile carbon. 

Co arene chemistry has been expanded by the preparation of a number of (arene)Co(j7" -diene)+ and (arene)Co( , -enyl) complexes starting from (10). Hydrogenation of (10) in the presence of an arene and a base (piperidine or quinuclidine for obvious stabilization of coordinatively unsaturated cobalt intermediates) gives cyclooctenyl complexes (37) (equation 53). This reaction occurs with a large niunber of arenes even CeFg gives an j -arene complex. The resulting complexes (37) are moderately active catalysts in the pyridine synthesis from alkynes and nitriles (Section 5.1.4). 

In contrast to carbocyclic alkyne cyclotrimerizations, the catalytic pyridine synthesis from alkynes and nitriles relies exclusively on cobalt catalysts with a few exceptions where rhodium [16] and iron complexes [17] could be applied. The cobalt-catalyzed pyridine synthesis can even be carried out in a one-potreac-tion generating the catalyst from C0CI2 6 H20/NaBH4 -1- nitrile/alkyne in situ [18]. 

Cobalt-catalyzed synthesis from alkynes and nitriles 85AG264 86MI13 ... 

The first application of phosphinines in catalysis was reported by Zenneck et al. in 1996 in the case of t 6-Fe complexes [46, 98], It was shown that complex 73 could catalyse the cyclotrimerization of dimethyl acetylenedicarboxylate as well as the formation of pyridines from alkynes and nitriles. Importantly, the catalytic activity of this complex was found to be superior to that of the corresponding benzene [Fe(n6-C6FI6)(COD)] complex. Reactions of methylpropargyl ether with butyronitrile in the presence of complex 73 as catalyst in a ratio 620 2,720 1 afforded a mixture of functional benzenes and pyridines. Turn over numbers (TON) for the conversion into pyridines reached 160 and those for the formation of functional benzenes reached 326, thus corresponding to a chemoselectivity of 0.49 (Scheme 26). 

Efficiency of pyridine synthesis from alkynes and nitriles is improved with light (Scheme 3) <93AOC(7)641>. 

A brief review of the cotrimerization of alkynes with nitriles to give pyridines has appeared. Pyridine itself is produced from C2H2 and HCN in benzene at 110 C/60 min under 23 bar pressure. The borabenzene complex (54) as the catalyst gives 103 turnovers. The catalytic formation of substituted thiophenes from alkynes and elemental sulfur in the presence of [CPC0L2] catalysts is also mentioned. Analogous rhodium complexes [Cp RhL2] also catalyze the formation of pyridines. 

Uses Catalyst for synthesis of pyridines from alkynes and nitriles polymerization inhibitor of olefins up to 200 C in Diels-Alder reactions as paint drier oxygen stripping agent Manuf/Distrib. Acres Org. http //www.acros.be-, Aldrich http //www.sigma-aidrich.com, Alfa Aesar http //www.aifa.com, Boulder Scientific Pfaltz Bauer http //www.pfaltzandbauer.com Strem Chems. http //www.strem.com... 

Alkynyltrialkylborates are versatile intermediates to 1,4-dikelones and y-oxo-esters, -nitriles, and -alkynes, as well as substituted ketones. A route from a -unsaturated cycloalkenones to 1,4-diketones is available wherein an aldehyde undergoes photoaddition to the alkene unit, and a variety of 1,4-diones is obtained by thiazolium salt-catalysed addition of aldehydes to but-2-enone. Monoacetalized 1,4-diketones and y-keto-aldehydes are formed on reaction of acyl chlorides with the Grignard reagents (13) and (14), respectively. 

H. Bonnemann, Cobalt-Catalysed Pyridine Synthesis from Alkynes and Nitriles , Angew. Chem. Internat. Edn., 1978,17, 505. 

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