Isonitriles tetrazoles

Azides have been shown to react with itniniutn salts to give addition products. The same product is obtained if the iminium salt is treated with azide ion or if the enamine is treated with hydrazoic acid 14). The yields of the products were all very high (85-95 %). The interest in this reaction centers on the fact that the azides react with isonitriles to give substituted tetrazoles (83) 44). 

The main difference in the thermolysis of tetrazolinones (44) and tetrazolinethiones (45) is the generation of sulfur (S2) and hydrogen sulfide from the latter compounds. The sulfur atom is split off from the starting molecules and not from a thermolysis product such as an isothiocyanate in a secondary reaction. The sulfurless tetrazole is then cleaved by cycloreversion, affording the corresponding isonitrile as a product that cannot be explained otherwise. There is little in common between photolysis and thermolysis of... 

The multicomponent Ugi-type condensation of aldehydes, secondary amines, azide, and polystyrene-bound isonitriles has been reported to yield tetrazoles in acceptable yields (Entry 9, Table 15.20). Tetrazoles have also been prepared from... 

Reactions between 5-cyanotetrazole and transition metals, when performed in boiling acetone, lead to hydrolysis of the cyano group and formation of 5-carbamyl tetrazolate complexes (68). Complexes containing 1- or 5-substituted tetrazolate anions can also be obtained by 1,3-dipolar cycloaddition of organic isonitriles (RNC) (15) or nitriles (RCN) (61), respectively, to coordinated azide ligands [Eqs. (3) and (4)]. 

R CO-5-R-ttaH) tetrazoles, respectively (114). The azide Pd(N3)2-(PPh3)2 also undergoes 1,3-cycloaddition reactions with organic isonitriles (RNC) (15) and isothiocyanates (RNCS) (114) to afford the complexes 42 and 43 (M = Pd), respectively. N-l-Coordinated tetrazolate chelate complexes 44 and 45 are formed by treatment of... 

Addition of azide ion to nitriles, nitrilium ions and isonitriles The addition of the azide anion to nitriles is the most widely used route to 5-substituted tetrazoles (203). This reaction can prove highly sensitive to the nature of the cation and the type of solvent used. It is also sensitive to the nature of the substituent R of the nitrile and it works best when R contains electron-withdrawing groups. In hydroxylic or alcoholic solvents the reaction usually requires a few days at reflux temperatures and the yields may be medium or poor. The best conditions tend to be in dipolar aprotic solvents such as DMF, using ammonium azide as the source of azide ion. The work-up procedures... 

Triple bonds add azides to give 1,2,3-triazoles (from carbon-carbon triple bonds) and tetrazoles (from nitriles or isonitriles). The reactions are of very wide scope, but there are few examples involving acyl azides. The formation of triazoles from acetylenes and azides in general has been reviewedand the scope of these reactions has been expanded by more recent work, a few examples of which are found in the references 255-25s triazole formation from acetylenes... 

Related methods can be used to prepare 5-hetero-substituted compounds isonitriles with A-halo-succinimides and azide give halo derivatives, aryl isothiocyanates with azide give the 5-thiols, ° which can be converted into 5-unsubstituted tetrazoles by oxidation with hydrogen peroxide or chromium trioxide. ... 

Tetrazoles are interesting functionalities with versatile applications, such as for lipophilic spacers [172], in explosives [173,174] and as precursors to several nitrogen-containing heterocycles [175,176]. Beside lutrUes, isonitriles (= isocyanides) can act as dipolarophUes in cycloaddition reactions with azides. Those reactions lead to 1-substituted tetrazoles and are described as welL 1-Substituted tetrazoles have also received much attention because of their wide utility [ 177-179]. 

Beside all described syntheses of tetrazoles from nitriles and azides, l-sub-stituted tetrazoles, which are synthesized from isonitriles, have also received much attention [177-179]. 

Scheme 63 Reaction of isonitriles 307 with iodine azide towards 1,5-substituted tetrazoles...

Additionally, for catalyzed reactions, an example for synthesis of tetrazoles by reacting isonitriles and azides was reported. Yamamoto et aL reported that the acid-catalyzed [3-1-2] cycloaddition between isocyanides 322 and trimethylsUyl azide (146) in the presence of methanol gives the desired 1-substituted tetrazoles 323 in good yields (Scheme 68) [ 177-179). 

By varying the nucleophilic component in the U-4CR, a variety of heterocyclic compoimds may be synthesized. Such an example is illustrated in the one-pot synthesis of fused tetrazole-ketopiperazines, as demonstrated by Hulme and co-workers. The treatment of trimethylsilyl azide (38) with amine 37, isonitrile 39, and aldehyde 40 gave the intermediate tetrazole 41 that underwent spontaneous lactamization to afford 42. In this report, the formation of [3.4.0]-bicycles proceeds in good to excellent yields for all examples. However, attempts to form [3.5.0]-bicyclic systems using methyl-P-isonitrile propionate resulted in significantly decreased yields. 

It also ruled out the formation of the tetrazole from the prior reaction of the corresponding formylamide with trimethylsilyl azide, which is a viable alternative reaction pathway [64]. In fact, the reaction of only the isonitrile with the capsule led to the formation of the corresponding formylamide and subsequent addition of trimethylsilyl azide to the this solution did not lead to the formation of the corresponding tetrazole. 

Giust S, La Sorella G, Sperni L, Fahris F, Strukul G, Scarso A. Supramolecular catalysis in the synthesis of substituted 1 H-tetrazoles from isonitriles by a self-assembled hexameric capsule. Asian J Org Chem 2015 4 217-20. 

The azide ligand of a PMes complex reacts with isonitrile to form a complex with 67-coordinated tetrazolate rings (243-245, Equations (69) and (70)). " " Insertion of isonitrile into the Pt-N bond is followed by cyclization via intramolecular nucleophilic attack at the coordinated carbon atom. Since the tetrazolato ring is perpendicular to the square-planar coordination plane, the trans-complcx with two 5-alkyltetrazolate ligands exists as a mixture of isomers with the alkyl substituents in syn- and < //-orientations 244 and 245. 

Scheme 31.1 (a) The products obtained from the catalytic reaction of 4-phenyl-butyne (19) with 18 both in the presence and absence of water [53a]. (b) Addition of TMSN3 to isonitriles to obtain a series of substituted IH-tetrazoles [53d]. (c) 1,3-Cycloaddition reaction between diazoacetate esters (26) and electron-poor alkene (27) to obtain 4,5-dihydro-IH-pyrazole derivatives (28) [53e]... 

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