From arylhydrazones

The 1,3-dipolar cycloaddition of diarylnitrile imines 98, generated in situ from arylhydrazones with chloramine T or from a-chlorobenzylidenephenylhydrazine with triethylamine, to some 5-substituted 2-methylpyridazin-3(2//)-ones 88, 99-101 has been shown to afford l,3-diaryl-l,5-dihydro-4//-pyrazolo[3,4- ]pyridazin-4-ones 102 regioselectively (Scheme 21) <2000JMT(528)13>. [Pg.31]

Processes include the Fischer indole synthesis from arylhydrazones and related sigmatropic syntheses, reductive evclizations of nitni compounds, the Madelung synthesis from anilides and related base-cululyxed condensations. and transition-metal catalyzed cyclizations,... [Pg.826]

Fischer indole synthesis Preparation of indoles from arylhydrazones of ketones and aldehydes in the presence of protic or Lewis acid catalyst. 172... [Pg.509]

Ginnolines from arylhydrazones via N-alkylideneamino-N-aryloxamyl chlorides and 1-alkylideneaminoisatins Stolle-Becker rearrangement... [Pg.433]

The issue of regioselectivity arises with arylhydrazones of unsymmetrical ketones which can form two different enehydrazine intermediates. Under the conditions used most commonly for Fischer cyclizations, e g. ethanolic HCI, the major product is usually the one arising from the more highly substituted enehydrazine. Thus methyl ketones usually give 2-methy indoles and cycliz-ation occurs in a branched chain in preference to a straight chain. This regioselectivity is attributed to the greater stability of the more substituted enhydrazine and its dominance of the reaction path. [Pg.56]

Another issue of regioselectivity arises with meta-substituted arylhydrazones from which either 4- or 6-substitutcd indoles can be formed. Robinson has tabulated extensive data on this point[9]. A study comparing regioselectivity of cyclization as catalysed by HCl/EtOH and ZnClj was carried out for several m-substituted arylhydrazones of diethyl ketone[10]. The results given in Table 7.1 show some dependence on catalyst but mixtures are obtained under all conditions studied. [Pg.58]

Jacobson-Hugershofi synthesis benzothiazoles, 5, 135 Japp-KJingemann reaction JV-arylhydrazones from, 4, 337 1,2,4-triazole synthesis by, 5, 768 Jasmine lactone synthesis, 3, 847 Jasminine occurrence, 2, 626 y-Jasmolactone synthesis, 4, 674 cis-Jasmone synthesis, 1, 422, 427 Jatropham synthesis, 1, 426 Josephson junctions, 1, 359 Juliprospine... [Pg.693]

The first indolization of an arylhydrazone was reported in 1983 by Fischer and Jourdan" by treatment of pyruvic acid 1-methylphenylhydrazone 3 with alcoholic hydrogen chloride. However, it was not until the following year that Fischer and Hess identified the product from this reaction as 1-methyl indole-2-carboxylic acid 4. [Pg.116]

Surprisingly, arylhydrazones 88a-d, upon treatment with 1-benzenesulfonyl-hydrazide 89 in refluxing ethanol, afforded very good yields of pyrazol-3-ones 90a-d (85JIC54) (Scheme 25). 5-Aminopyrazol-3-(Mies have also been synthesized from /3-cyanoesters (Section II,A,2) and from /3-iminoesters (Section II,A,3). [Pg.92]

Arylhydrazones from reaction of /3-dicarbonyl compounds with arenediazonium salts... [Pg.173]

Other non-traditional preparations of 1,2,3-triazoles have been reported. The rearrangement in dioxane/water of (Z)-arylhydrazones of 5-amino-3-benzoyl-l,2,4-oxadiazole into (2-aryl-5-phenyl-27/-l,2,3-triazol-4-yl)ureas was investigated mechanistically in terms of substituents on different pathways <06JOC5616>. A general and efficient method for the preparation of 2,4-diary 1-1,2,3-triazoles 140 from a-hydroxyacetophenones 139 and arylhydrazines is reported <06SC2461>. 5-Alkylamino-] //-], 2,3-triazoles were obtained by base-mediated cleavage of cycloadducts of azides to cyclic ketene acetals <06S1943>. Oxidation of N-... [Pg.229]

In the presence of sodium acetate in acetic acid, the arylhydrazones 54 (available from the reaction of tu-halogen-tu-(arylhydrazono)acetophenones with 3-amino[l,2,4]triazole) undergo cyclization to yield 3-aroyl-l-aryl-l//-[l,2,4]-tria-zolo[3,4-c][l,2,4]triazoles 55 (Equation 7) <1987CB965>. [Pg.334]

The issue of stereoselectivity of the vinyllithium formed from acyclic arylhydrazones has also been addressed. For symmetrical linear-chain ketone derivatives such as 105, the -vinyllithium 106 is the exclusive product (equation 36)362,367-372... [Pg.475]

Construction of the indole ring via Fischer synthesis. Starting from a variety of 3,4-dihydro-lH-benzo[l ]azepine-2,5-diones 40 and arylhydrazines Fischer syntheses of indolo benzazepinones 41 have been reported (Scheme 8 (1999JMC2909)). Usually, the reaction comprises a two-step one-pot procedure with the formation of intermediate arylhydrazones in warm acetic acid followed... [Pg.8]

The synthesis of cyclic ethers 137 was achieved by a Fischer indole synthesis starting from cyclic keto arylhydrazones generated in situ from 4-(hydroxy-methylene)-3,4-dihydrobenzo[ 7]oxepin-5(2H)-one 136 and the corresponding diazonium salt (Equation (20), 1993JHC1481). [Pg.23]

Mild oxidation of o-nitrobenzaldehyde arylhydrazones with either bromine and sodium acetate or lead tetraacetate results in the overall loss of two hydrogen atoms and production of a class of iV-aryl heterocycles, tiie structure of which was the subject of uncertainty and some controversy for more than fifty years. These oxidation products were first prepared and investigated by Chattawayj " who described them as isodiazomethanes and formulated them as the triaziridine derivates 72. Structural assignment was based entirely on evidence from degradation studies in particular, Chattaway showed that reduction of... [Pg.233]

Alkyl-3-formylcarbazoles form-arylhydrazones " and azines or hydrazones with hydrazine. 9-Ethyl-3-formylcarbazole gives Schiflf bases with arylamines. Variously substituted 3-formylcarbazoles condense with aminoacetal, " and the resulting imines are easily reduced catalytically or with sodium borohydride. Anils from... [Pg.149]

Several examples of the mesoionic 3-aryl-l,2,3,4-oxatriazole-5-oxide ring system 123 have been prepared by cyclisation of the arylhydrazones 122 these in turn are prepared from aryldiazonium salts and bromonitromethane <99KGS413>. [Pg.233]

The tricyanovinylpyrazoles 67, isolated from reaction of tetracyanoeth-ylene (TCNE) with 51 (R1 = H,Ph R2 = H, Me), cyclized in refluxing acetic anhydride to 68.76 Analogous products (68 R1 = Ar,R2 = Me) were obtained from thermolysis or photolysis of the charge-transfer complex 69 formed between TCNE and arylhydrazones.77... [Pg.358]

Ilac Fischer indole synthesis from /V-arylhydrazones 3.06.3.4.2... [Pg.315]

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