Complex of isoxazole

Synthesis of Complexes of Isoxazole (Is) with Titanium(IV) Chloride [14b]... 

Despite the weak basicity of isoxazoles, complexes of the parent methyl and phenyl derivatives with numerous metal ions such as copper, zinc, cobalt, etc. have been described (79AHC(25) 147). Many transition metal cations form complexes with Imidazoles the coordination number is four to six (70AHC(12)103). The chemistry of pyrazole complexes has been especially well studied and coordination compounds are known with thlazoles and 1,2,4-triazoles. Tetrazole anions also form good ligands for heavy metals (77AHC(21)323). 

Incorporation of isoxazole instead of pyrazole has similar affects. Ni11 complexes with Schiff bases having pyrazole or isoxazole subunits and linkers with n = 4 (503, 504) form a flattened tetrahedron with the dihedral angle (for the pyrazole derivative) between two N—Ni—S planes being 12.7°.1354 In solution a spin equilibrium and racemization process A -- A is observed. 

The chemistry outlined in Scheme 24 was then put into effect catalytic hydrogenation of the tris-isoxazole (302) and recyclization with triethylamine gave a tricyclic ligand which was chelated with nickel ions to give (303). Introduction of the fourth nitrogen atom was accomplished by treatment of (303) with ammonium acetate, giving (304). Treatment with cyanide removed the nickel ion which was then replaced with zinc(II) to give (305). The reasons for this transmetallation step were two-fold firstly, zinc(II) corrins, as shown by Eschenmoser, can be readily demetallated, and this fact opens up many options later in the synthesis, but secondly, and more importantly, Eschenmoser s photochemical cyclization of seco-corrins (see Section 3.07.3.4.2.3) does not proceed with nickel complexes of seco-corrins, whereas zinc(II) seco-corrins can be cyclized in almost quantitative yield... 

In oxazole (167) (95MI5) and isoxazole (168) [88ZN(B)328] N-M coordination prevails. The possibility of O coordination (169) is less likely. Examples of the C-coordinated derivatives of oxazole (170) and isoxazole (171) are known [89JOM(372)287]. The complexes of composition CrL2 based on 3-methyl-5-phenyl- and 3,5-diphenylisoxazole were assigned a polymeric structure with the -coordinated framework (78ZOB418). The other example is the interaction of the cyano complexes [M(CN) (cp)(dppe)] (M = Fe, Ru) or [Fe(cp)(dppe)(CNH)]Br with gem-dicyano-epoxide to afford the oxazol-2-yl complexes with the C-coordination mode... 

Isoxazole (L) complexes of stoichiometry CdLX2 (X = Cl, Br, I or NCS) have been prepared.462 IR evidence indicates them to be tetrahedral, dimeric, anion-bridged complexes, with N coordination. 

Other reagents recommended for the reduction of isoxazoles to 1,3-enaminoketones include samarium diiodide, molybdenum hexacarbonyl in aqueous acetonitrile, and diiron nonacarbonyl in water. Electrochemical methods have also been employed." A particularly mild method involves reaction with the reduced form of the coenzyme lipoamide (LA2) complexed with iron(II). Birch reduction (sodium and... 

Methylisoxazole-5-carboxylic acid was converted into the corresponding 5-carboxamides and 5-(l/7-pyrazol-l-ylcarbonyl) derivatives in satisfactory yields by treatment with thionyl chloride and amines or pyrazoles <2002SC425>. A three-component assembly of isoxazole-5-carboxylic acid chloride, 1,1-dimethylallene, and bis-pinacolatodiboron, catalyzed by a phosphine-free palladium complex, gave 2-acylallylboronate derivatives regiose-lectively (Equation 47) <2003JA12576>. On the other hand, a mild procedure allowed the preparation of /3,7-unsaturated ketones by simple reaction of 3-aryl-5-methylisoxazole-4-carboxylic acid chlorides with allyl bromide and indium in DMF (Equation 48) <1997TL8745>. 

In more specific work, adducts of the form TiCl4Lo have been prepared and reported. These include complexes where L = TMEDA,16 benzotriazole,17 benzothiazole,18 2-aminobenzimidazole,19 2-methyl-2-oxazoline, thiazole and a variety of oxazole-derivatives.20 Similarly, complexes of the form TiCl4L (L = RC6H4NH2, R=Bu , Cl, N02, Me21,22 isoxazole, 5-methylisoxazole,20 2-aminobenzimidazole, 2(2 -aminophenyl)benzimidazole,19 2-pyridylphenylacetonitrile22) have been reported. Schifif base adducts of TiCl4 derived from A-methylpyrrole-2-carboxaldehyde, 4-methyl-benzaldehyde, salicylaldehyde, and aromatic or aliphatic amines have also been characterized.23-25 A variety of 2 1 substituted silyl-amine-Ti adducts have also been reported 26-28... 

X-ray analysis has aided in establishing the structure of isoxazoles <92JCS(P2)121, 92JHC1325, 93JCS(Pi)939) and transition metallic complexes <89JOM(372)287) unequivocally. 

There are general reviews on heterocyclic syntheses by cycloaddition reactions of isocyanates and on the use of heterocyclic cations in preparative organic chemistry. More specific topics are 5-hydroxymethylfuran-2-carb-aldehyde, isobenzofurans and related ort/io-quinonoid systems, the conversion of 2//-cyclohepta[Zj] furan-2-one (1) into derivatives of azulene, the synthesis of indoles from o-alkylphenyl isocyanides, and abnormal Fischer indolization reactions of o-methoxyphenylhydrazones. Two reviews on isoindoles have appeared and a lecture on highly conducting charge-transfer complexes that are based on heterocyclic selenium and tellurium donors has been reprinted.Recent advances in the chemistry of imidazole and in the use of nitro-imidazoles as radiosensitizers have been summarized. There have been reviews on benzimidazole A -oxides and on dihydrobenzimidazoles, benzimidazolones, benzimidazolethiones, and related compounds. Other topics are synthetic applications of 1,3-dithiolium and 1,3-oxathiolium salts and of isoxazoles, the chemistry of benzisoxazoles, 2-amino-oxazoles, 5-oxazolones (2), furoxans, benzofuroxans, and related systems, the synthesis of five-membered meso-ionic compounds, and tetrazoles. ... 

The early work on the formation of isoxazole derivatives by the action of primary amines on dibenzoylfuroxan has been summarized elsewhere.3-5 The whole area is still a very complex and confused one, despite a number of more recent studies. Since most of the products of these reactions are now assigned pyrazole or furazan structures, the discussion is deferred to the following Section (V,C,2). Here we mention the isoxazole derivatives that are produced. 

The oxidation of benzylbenzimidazole group in the synthesized copper complex of l-benzyl-2-[(5-methyl-isoxazol-3-yl)methyl]-benzimidazole to ketone follows first-order kinetics. 

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