Diazo compounds, aliphatic aromatic

The reaction of azide ions with aliphatic diazo compounds was investigated by Kirmse et al. (1979 for a discussion see Zollinger, 1995, Sec. 6.1). Here we mention only that cyclopropanediazonium ions react similarly to the aromatic diazonium ions, i.e., by TV-coupling to 1-cyclopropylpentazene and dediazoniation to cyclopropyl azide. In about 60% of the 1-cyclopropylpentazene the cyclopropyl azide is formed directly by dediazoniation of the original diazonio group, while in 40% the route is via the cyclopropylpentazole. 

The reaction of diazo compounds with amines is similar to 10-15. The acidity of amines is not great enough for the reaction to proceed without a catalyst, but BF3, which converts the amine to the F3B-NHR2 complex, enables the reaction to take place. Cuprous cyanide can also be used as a catalyst. The most common substrate is diazomethane, in which case this is a method for the methylation of amines. Ammonia has been used as the amine but, as in the case of 10-44, mixtures of primary, secondary, and tertiary amines are obtained. Primary aliphatic amines give mixtures of secondary and tertiary amines. Secondary amines give successful alkylation. Primary aromatic amines also give the reaction, but diaryl or arylalkyl-amines react very poorly. 

These authors also prepared novel epoxy-bridged cyclooxaalkanones in this process, the carbonyl group always acts as 1,3-dipolarophile, even if one employs ct,(3-unsaturated aldehydes. Thus, reaction of 6/2-16 with aliphatic or aromatic aldehydes 6/2-17 in the presence of catalytic amounts of rhodium acetate gave 6/2-18, regioselectively. With the a, 3-unsaturated aldehydes 6/2-20, only cycloadducts 6/2-21 were obtained using the diazo compound 6/2-19 as substrate (Scheme 6/2.3) [191]. 

Nor can there be any question of real tautomerism in the case of phenol. In its chemical properties phenol resembles the aliphatic enols in all respects. We need only recall the agreement in the acid character, the production of colour with ferric chloride, and the reactions with halogens, nitrous acid, and aromatic diazo-compounds (coupling), caused by the activity of the double bond and proceeding in the same way in phenols and aliphatic enols. The enol nature of phenol provides valuable support for the conception of the constitution of benzene as expressed in the Kekule-Thiele formula, since it is an expression of the tendency of the ring to maintain the aromatic state of lowest energy. In this connexion the hypothetical keto-form of phenol (A)—not yet obtained—would be of interest in comparison with... 

The mechanism of the coupling reaction has been very exhaustively studied. Summarising first what has already been mentioned, it must be noted that the reaction is not confined to the aromatic series, for diazo-compounds condense also with enols and with the very closely related aliphatic aci-nitro-compounds. The final products of these reactions are not azo-compounds, but the isomeric hydrazones formed from them by rearrangement. 

In contrast to the epoxides, preparative routes to the aziridines are fairly evenly split between the [C=N + C] and the [C=C + N] routes. Among contributions in the former category, aziridine carboxylate derivatives 110 can be prepared through the lanthanide-catalyzed reaction of imines with diazo compounds, such as ethyl diazoacetate (EDA). In this protocol, iV-benzyl aryl aldimines and imines derived from aromatic amines and hindered aliphatic aldehydes are appropriate substrates <99T12929>. An intramolecular variant of this reaction (e.g.. Ill —> 112) has also been reported <990L667>. 

H. Zollinger, Azo and Diazo Chemistry—Aliphatic and Aromatic Compounds. Wiley (Interscience), New York, 1961. 

Diazochemistry- Title of a book by Heinrich Zollinger, "Azo and Diazo Chemistry-Aliphatic and Aromatic Compounds", Inter-science, NY.( 1961)(Translated by Harry E. Nurs ton). 

Organic azides (RNS) are isoelectronic with diazo-compounds, and like them are yellow in colour. On irradiation azides lose nitrogen to produce monovalent nitrogen species, nitrenes lRN . In the absence of an addend, aliphatic nitrenes generally undergoa shift of hydrogen to give an imine (5.34), whereas aromatic nitrenes can dimerize to yield an azo-compound (S.3SI. 

The reaction of azides with ethoxyacetylene (98) has been studied by Italian authors. With aliphatic and aromatic azides, the expected 1-substituted 5-ethoxy-l,2,3-triazoles (99) are obtained.310-311 Sulfonyl azides, on the other hand, react with ethoxyacetylene at room temperature to yield no triazoles but the valence tautomeric diazo compounds (100).312-313... 

A number of acyl silanes have been isolated from the photosensitized oxygenation of silyl diazo compounds using meso-tetraphenylporphine (TPP) as the sensitizer (Scheme 15)15. This synthesis is most useful for aromatic acyl silanes and the yellow u-carboxyacyl silanes, but it is not of general applicability, isolation difficulties commonly being encountered in the synthesis of aliphatic and other acyl silanes, resulting in poor overall yields. 

The chemistry of aliphatic diazo compounds of the general formula RCHNj, among which are the important diazo ketones RCOCHN, and diazo esters NjCRCOjR, has been reviewed. " In addition, the formation of aromatic diazonium salts, ArN CF, has been extensively studied and fully described in several monographs. For this reason, only the most pertinent points are included here along with key references. 

For example, unbranched aliphatic acids with an even number of carbon atoms will be generously represented, while one finds a nearly complete absence of odd-numbered and branched acids. Nature produces an incredible diversity of the most ingeniously constructed cyclic products containing cycloaliphatic, aromatic, or heterocyclic moieties, but such derivatives like aniline or thiophe-nol, as well as plethora of other simple representatives of these classes, are not in the list of naturally occurring substances. Such important types as alkyl halides, nitro compounds, and diazo compounds would be sparsely represented by very rare (if any) examples. Even the simplest compounds like formaldehyde, chloroform, diethyl ether, dioxane, etc., which are trivial to organic chemists, turn to be rather exotic for Nature. In the list of items provided by Nature one will notice the almost complete absence of various organometallic compounds, as well as many other classes of structures of immense scientific and practical significance. 

A few examples of the reduction of aliphatic diazo compounds to hydrazines exist," but this is not a generally applicable method for the synthesis of alkylhydrazines. On the other hand, arylhydrazines can be prepared by reduction of aromatic diazonium salts.The most commonly used reagents for this conversion are sulfur dioxide (or sodium sulfite) and tin(II) chloride, these being used to reduce arenediazo-nium chlorides in aqueous solution. Several other reagents, including sodium amalgam and triphenylphosphine, have been used for specific reductions of this type. Arenediazonium tetrafluoro-borates have been reduced to the correspwnding hydrazinium salts (3) by benzeneselenol in dichloro-... 

Peter Griess, 1858.—Diazo compounds were discovered and first prepared by Peter Griess in 1858. The historical method used by him is the same in general as is now used widely in dyestuff manufacture. It has already been described and consists in the action of nitrous acid on an aromatic primary amine, e.g., aniline. When this reaction takes place, at ordinary or slightly raised temperatures, the same products are obtained as with aliphatic primary amines, viz., the hydroxyl compound of the hydrocarbon radical, free nitrogen and water. 

Solvents are commonly dimethylformamide, a chloroalkane or chloroalkene (methylene chloride, chloroform, 1,2-dichloroethane, etc.) or phosphoryl chloride. Temperatures used are generally in the range CM00 C.la Substrates include activated aromatic or heteroaromatic compounds, alkenes (including enamines and enol derivatives), methyl or methylene ketones and "active methyl or methylene groups in general, and hydrazones, azines and aliphatic diazo compounds. 

As already mentioned, under the preparation of methyl amine, the behaviour of the aliphatic primary amines toward nitrous add is very different from that of the aromatic compounds. While the former yield alcohols with the elimination of nitrogen, the latter, in a mineral acid solution, under the influence of nitrous add, yield diazo-compounds, discovered by Peter Griess, in the form of thdr mineral add salts. 

Zollinger H., Azo and Diazo Chemistry. Aliphatic and Aromatic Compound,s . Interscience, New York. (1961)... 

Regitz et al. studied the chemistry of the benzoylphosphene (372), generated photochemically from the diazo-compound (371), Benzophenone adds in a (4 -I- 2)-cycloaddition process, to form the pentaphenyl-2//,6//-l,5,2-oxaphosphinine 1-oxide (373) (Scheme 78). Other aromatic and aliphatic aldehydes and ketones cycloadd in a similar fashion <73AG(E)1010,78CB705,78CB726). 

Aliphatic Diazo Compounds.—It has been stated that primary aliphatic amines do not yield diazonium compounds when treated with nitrous acid. It is of interest to note, however, in connection with the aromatic diazo compounds, that certain derivatives of the ahphatic amines yield compounds when treated with nitrous acid which resemble somewhat in their reactions the diazonium compounds. When the ethyl ester of amino-acetic acid is treated with nitrous acid a yellow oil is obtained, which explodes when heated. The reaction takes place according to the equation,—... 

The most comprehensive and recent overview on diazo compounds are the corresponding volumes of Patai s work The Chemistry of Functional Groups, namely the two volumes on diazonium and diazo groups (Patai, 1978), the two volumes on hydrazo, azo, and azoxy groups (Patai, 1975), and the two Supplement C volumes on triple-bonded groups (Patai and Rappoport, 1983). Volumes on diazo and diazonium groups (Patai, 1978) contain chapters on aromatic and aliphatic compounds. There are also chapters in which certain aspects of aromatic and aliphatic compounds are treated together. These volumes do not contain chapters on alkene-... 

The diazo transfer method 6 is also used for aromatic diazonium salts (see Zollinger, 1994, Sect. 2.6). Diazo transfer is, however, more relevant for the synthesis of aliphatic diazo compounds. In addition to the schematic presentation in Table 2-1, the transfer of N2 from the azide to the carbanion may be combined with the dissociation of certain groups attached to the anionic carbon (see Sects. 2.6 and 2.7). 

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