Diazo-derivatives

The reaction of phosgene with diazomethane in a molar ratio of 1 2 gives the previously unknown diazo compound, N2CHC(0)C1 [185]  

Both chloroethanoyl chloride, ClCHjC(0)Cl, and 1,3-dichloropropanone, CICHjC(0)CHjCl, are formed as by-products. The former is a result of the combination of NjCHC(0)Cl with liberated HCl, and the latter is formed by the reaction of the former with the excess of diazomethane to give the diazoketone, N jCHC(0)CHjCl, which then itself reacts with HCl [185]. In the presence of triethylamine, using a COCl rCHjNj ratio of 1 4, the diazoketone, N jCHC(0)CHjCI, is the sole product [185]. 

A solution of 2,2,2-trifluorodiazoethane in dichloromethane was treated with finely powdered dipotassium bydrogenphosphate and phosgene at room temperature to give 2-diazo-3,3,3-trifluoropropanoyl chloride [375]  

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The behaviour of pyrazoles towards nitrosation is similar to their behaviour described above towards diazo coupling, i.e. aminopyrazoles and pyrazolones readily react with nitrosation agents, like alkyl nitrites (81FES1019), to afford stable nitroso derivatives. Some simple nitrosopyrazoles have been isolated, for example the blue-green 3,5-dimethyl-4-nitrosopyrazole, and many others have been proposed as reactive intermediates in the direct conversion of pyrazoles into diazonium or diazo derivatives (Scheme 25) (B-76MI40402). 

Nitiosobenzene, which shares the general character of nitroso-compoLinds in gnung rise to a gneen vapour or solution, is leadily reduced to phenylhydroxylamine and aniline. It condenses with ammo-compounds, yielding azo- or diazo-derivatives. 

All the same, lasting credit is due to Hantzsch for refuting the proposals, made so often since 1894, to interpret the isomerism of diazo derivatives using other than stereochemical arguments. For his purpose Hantzsch used the methods of physical chemistry, such as conductivity measurements and spectroscopy, at a time when these were most unusual in the organic field. 

Oxaestrone has been synthesised from 7-methoxychroman-4-one <96JCS(P1)841>. Formation of the complex chroman-3-one (16) by a Dieckmann reaction and its conversion to the 4-diazo derivative are signifcant steps in the synthesis of the pentacyclic system (17) <96TL5243>. 

Since the regioselectivity of mercuration reactions is often hard to control, recent efforts have focused on the use of Lewis-basic substituents whose role is to direct the approach of the mercuric ion to a specific position. Reaction of the diazo derivative 74 with Hg(OAc)2 leads to mercuration of the naphthalene moiety in the 8-position rather than mercuration of the electron-rich imidazole carbon atoms. 4 Presumably, the diazo-imidazole bidentate moiety coordinates to the mercuric cation, thereby directing substitution at the naphthalene 8-position (Equation (27)). 

Some diazirines, particularly the 3-trifluoromethyl-3-aryldiazirines, can rearrange upon photolysis to a linear diazo derivative, similar in structure to the photosensitive end of the crosslinker PNP-DTP (Chapter 5, Section 3.12). These isomerized products themselves can be photolyzed to the reactive carbene. 

Figure 4.31 Reaction of o-tolidine with sodium nitrite in the presence of HC1 yields a highly reactive diazo derivative.

Figure 5.29 pNPDP reacts with amine-containing compounds by its p-nitrophenyl ester group to form amide bonds. After photoactivation of the diazo derivative with UV light, a Wolff rearrangement occurs to a highly reactive ketene intermediate. This group can couple to nucleophiles such as amines. 

Figure 27.11 This diazo derivative of biocytin may be used to modify guanine bases at the C-8 position.

Coupling of 5-aminobenzotriazole 297 with a diazonium salt derived from 4-methoxyaniline generates diazo derivative 298. Conversion of the amino group into maleinimide produces dye 299 (Scheme 45). Diels-Alder cycloadditions of dye 299 to diene tagged nucleotides allows for their efficient labeling <2002CC2100>. 

The nitrile group in 82 has been transformed into other versatile functional groups, and the derivatives so obtained have been used in the synthesis of various naturally occurring C-nucleosides and their analogs. Reduction of 82 with lithium aluminum hydride gave the amine 90 which was, in turn, transformed84 into the ureido and N-ni-troso derivatives (91-93) by treatment with nitrourea, followed by benzylation, and nitrosation.85 The diazo derivative 94, obtained by treatment of 93 with alcoholic potassium hydroxide, was a key intermediate in the synthesis of formycin B and oxoformycin B (see Section III,2,a,b). 

Phosphorylated and thiophosphorylated diazo compounds, i -Pr2P(X)C(N2) SiMe3 (X = O, S) react with nitrosyl chloride to give a-nitroso-diazo derivatives... 

Liebermann-Burchard reaction diazo derivatives nitrated derivative... 

Triazoles (386, R1 = COOMe) were treated with potassium tert-butylate in a mixture of f r/-butanol and benzene for 15-60 min to give (substituted amino)methoxycarbonylmethylenemalonates (387, R1 = COOMe) in 28-54% yields. In the case of the acetyl derivative (386, R = Ph, R1 = COMe), the reaction was carried out in chloroform in the presence of triethylamine at ambient temperature for 8 hr, to give (pheny-lamino)acetylmethylenemalonate (387, R = Ph, R = COMe) in 38% yield. (Phenylamino)acylmethylenemalonates (387, R = Ph,R = COMe, COPh) were also prepared in 62-74% yields when diazo derivatives (388, R1 = COMe, COPh) were heated in benzene for 4-24 hr (80T1821) (Scheme 34). 

Methyl 2-substituted 4-hydroxyquinoline-3-carboxylates (564) were prepared in 41 -54% yields by heating diazo derivatives (562) in boiling toluene for 0.5-9 hr, via aminomethylenemalonates (563). H-NMR investigation revealed the formation of a 52 48 mixture of aminomethylenemalonate (563, R = COPh) and quinolinecarboxylate (564, R = COPh) when the diazo compound (562, R = COPh) was heated in toluene for 4 hr. A better yield was achieved when the triester (562, R = COOMe) was heated in boiling 1,2-dichlorobenzene (80T1821). 

The reaction of activated methylene groups with tosyl azide to yield the corresponding diazo derivatives proceeds in high yield [23]. The phase-transfer catalysed reaction is sensitive to the strength of base used the reaction of acetoacetic esters requires relatively mild conditions, otherwise diazoacetic esters are produced (Table 5.41). 

Most of the transient and all the stable phosphinocarbenes 2 have been prepared from the corresponding diazo derivatives 1. However, three other... 

In contrast to A5-phosphorus-substituted diazo derivatives, which have been known for a long time,22 the synthesis of the first o -diazophosphine was reported as recently as 1985.23 This compound, namely the [bis(diiso-propylamino)phosphino](trimethylsilyl)diazomethane la, was obtained by treatment of the lithium salt of trimethylsilyldiazomethane with 1 equiv of bis(diisopropylamino)chlorophosphine. 

Horton, D. and Philips, K.D., Diazo derivatives of sugars. Synthesis of methyl 2-deoxy-2-diazo-D-arahino-hexonate, its behaviour on photolysis and thermolysis, and conversion into a pyrazole derivative. Carbohydr. Res., 1972, 22, 151. 

Auch interessante analoge 4-Desoxy-4-diazo-Derivate sind erhaltlich n>8). 

The thiazofurin acyclic analog 925 was prepared from 924 as shown in the scheme (87H947). 1,3-Dipolar cycloaddition of the acetylenic derivative 927 to the diazo derivative 926 gave the pyrazole 928, whose amidation and debenzylation gave 929 (93MI11). 

Irradiation of 59a,c in benzene gave the corresponding 3-phenylindoles 62 (R = Ph) (66LA17). In the case of the 3-diazo-derivative 59a, a dark red dye having structure 61 was also isolated. Photolysis of 59a in anisole gave the para substitution products 62 (R = 4-OMe-Ph) whereas in ben-zonitrile or methyl benzoate, only dark red oily mixtures were obtained. 

Carbethoxy-4-diazo-l-phenylpyrazol-5-one (22a) (Scheme 88) was synthesized in 76% yield under mild conditions by direct introduction of the diazo group with the azidium salt 293 in sulfuric acid at room temperature [78H(10)199]. The easy introduction of the diazo group probably occurred because the a position of the ester was activated. On the contrary, tosyl azide failed to give the diazo derivative under the same conditions. Diazo transfer with this reagent only takes place under alkaline conditions, but in these reaction conditions, the diazo compound couples with the starting material. 

With less electron-rich pyrroles, hydrochloric acid can be used in the diazotization. The diazo compounds were isolated after neutralization with aqueous ammonia [84H(22)2269]. 3-Diazo-2,5-diphenylpyrrole, although efficiently prepared by diazotization of the 3-aminopyrrole, can also be prepared by oxidation of the 3-nitrosopyrrole with dinitrogen trioxide (60JCS3270). Pyrrole-3-carboxylic acid, with buffered nitrous acid, gave the 3-diazo derivative 295 by displacement of the carboxyl group, together with the 3-diazo-2-carboxylic acid 296, obtained by further hydrolysis (62JCS1638) (Scheme 90). 

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