Diazo coupling intramolecular

Benzenediazonium fluoroborate, 2-carboxy-xanthone synthesis from, 3, 838 Benzenediazonium ions phenyl azide formation from, 5, 839 Benzenediazonium salts, o-(imidazol-l-yl)-intramolecular diazo coupling, 5, 404 Benzene-1,2-disulfonimides N-substituted reactions, 6, 930 Benzene episulfide formation, 7, 577 Benzeneimine... 

In addition to the synthesis of industrially important azo dyes using heteroaromatic diazo components, intramolecular azo coupling reactions of heterocyclic diazonium ions also have interesting synthetic uses, because they lead to new fused-ring heterocycles, as shown by the diazotization of 2-amino-3-arylbenzimidazoles (12.7) in which, without isolation of the diazonium ion, a 1,2,4-triazine ring is formed (Kolodyazhnaya et al., 1973). Further examples of intramolecular azo couplings were reviewed by Tisler and Stanovnik (1980), and very extensively (403 references ) by Kishimoto et al. (1990). 

Intramolecular diazo coupling can be also achieved <85JCS(Pl)l3l). Starting from suitable (o-aminophenyl)thiophenes various isomeric thieno[c]cinnolines have been obtained (Scheme 24). The reaction can proceed either at an a- or at (3-position of the thiophene ring. 

Diazo ketones also possess an electrophilic diazo group, and hence are susceptible to diazo-coupling reactions with suitable soft nucleophiles. Examples are given in equations (11) and (12). Phospha-zines such as (19) are useful synthetic intermediates in their own right. The carbon terminus of the 1,3-dipole possesses nucleophilic properties and can participate in aldol-type reactions with the particularly electrophilic carbonyl groups in 1,2-di- and 1,2,3-tri-carbonyl compounds. Intramolecular condensations occur with greater ease (equation 13). Reaction of diazo ketones of the type summarized in equations (9)-(12) have been thoroughly reviewed. ... 

The synthesis and unusual chemical reactivity of certain novel 4,5-disubstituted 7-benzylpyrazolo[2,3-d][l,2,3]triazines 55 have been described. This unusual fused system, only two previous derivatives of which were known, has been obtained starting from diethyl 2-nitropyrrole-3,4-dicarboxylate 54 via an alkylation, ammonolysis, reduction and an intramolecular diazo coupling sequence <01 JOC4776>. 

For many decades intramolecular O-coupling was considered not to take place in the diazotization products of 2-aminophenol and its derivatives (for a contrary opinion see, however, Kazitsyna and Klyueva, 1972). The compounds were assumed to be present as one structure only, which can be represented as a mesomer of a phenoxide diazonium zwitterion 6.63 b and a diazocyclohexadienone 6.63 a (see reviews by Kazitsyna et al., 1966 Meier and Zeller, 1977 Ershov et al., 1981). In IUPAC nomenclature 6.63 is called 1,2-quinone diazide, in Chemical Abstracts 6-diazo-2,4-cyclohexadien-one (see Sec. 1.3). More recently, however, Schulz and Schweig (1979, 1984) were able to identify the intramolecular product of O-coupling, i.e., 1,2,3-benzooxadiazole (6.64) after condensation of 6.63 in vacuo at 15 K in the presence of argon (see Sec. 4.2). 

It has been reported that thermolysis of the bis(diazomethyl)phosphines lo leads to the formation of the diazaphospholes 64. This can be explained by either an intramolecular [2 + 3] cycloaddition process involving the diazo group, or a diazo-carbene coupling reaction. 

In the reaction of 4-diazotriazoles with morpholine, pyrrolidine [83DIS(B)(43)2557], and several other secondary amines (66JMC733), the corresponding triazenes 247 were obtained. Also, in the case of 4-diazo-l,2,3-triazole-5-carboxamide, these compounds could easily be obtained in organic solvents despite the competing intramolecular ring closure to 2,8-diazahypoxanthine. In aqueous media, the intermolecular coupling... 

Carbazole-1- and carbazole-3-amino groups have been diazo-and the diazonium salts coupled with 1,3-dike-tones and ethyl acetoacetate, used in Sandmeyer reactions, reduced to the hydrazines and made to effect intramolecular arylation of a 9-aryl group, such as in the transformation of 215 (R = Me or C02Me) into 216 (R = Me or C02Me). It is worth repeating the earlier observation... 

EtOH isopentane Et20) glasses at 77 K, four products 256, 257, 258 and 259 were obtained in overall >95% yield. The major product 256 was shown by isotopic labeling studies to have been derived from the silirene 260 formed by intramolecular coupling of the bis-carbene 261, and pathways for the formation of the other products were proposed. The photolysis of the bis-diazo compound 255 was studied in detail at 405 nm and it was found that the diazirine 262 was formed this on photolysis at 305 nm also gave 260 on the pathway to 256. The chemistry is shown in Scheme 46. 

Diazo-2-phenylindole (45) when heated with aqueous acid does not undergo intramolecular coupling like triphenyldiazopyrrole (21) but instead undergoes an intermolecular coupling with the elimination of nitrogen23 ... 

Diazo-3-benzyl-5-phenylpyrazole (52) undergoes an intramolecular coupling between the diazo group and the methylene group.31... 

Reactions of potentially high synthetic utility are intramolecular azo coupling reactions of heterocyclic diazonium ions to give new fused-ring heterocycles. Some examples are given in (25-27) . The use of heterocyclic diazo compounds in organic synthesis has recently been reviewed by Ti ler and Stanovink ,... 

Thioamides of two cyclopropanecarboxylic acids undergo coupling reactions with diazomethane derivatives in refluxing benzene containing rhodium(II) acetate. The reaction conceivably takes place via a thiirane intermediate which undergoes reductive elimination by reaction with excess diazo compound. An example of an intramolecular reaction is the formation of indolizine 2. If the diazo compound is not in excess a thiol is formed, this can be removed by Raney nickel desulfurization. ... 

Dimerization Reaction. Dimerization is another commonly encountered reaction of diazo compounds. Alcohol (16) is initially transformed into diazoester (17) with compound (1) and then converted to bisdiazocarbonyl compound (18). The Intramolecular coupling of this mixed diazo compound with a catalytic amount of Rh2 (OAc)4 produces a 1 1 mixture of (19) and (20). Furthermore, treatment of (19) with a catalytic amount of iodine quantitatively converts (19) to (20) (eq 12). ... 

Rhodium(lll)-catalyzed redox—neutral coupling of N-phenoxyacet-amides and alkynes led to benzo[l)]furan derivatives (13AGE6033). Furo[2,3-l)]pyran-6-one derivatives were prepared via rhodium(II)-catalyzed reactions of diazo compounds and ethynyl compounds (13T9294). Copper-mediated oxidative annulation of phenols and unactivated internal alkynes afforded benzo[l ]furan derivatives (13CS3706). E t-kaurane maoecrystalV was produced via C-H functionalization (13JA14552). Rhodium-catalyzed intramolecular C-H... 

---