Acetate, diazo

The reactions illustrated in equations (62-64) are each catalyzed by rhodium acetate. Diazo compounds, especially diazoalkanes, can also react by a simple ionic mechanism. The esterification of a carboxylic acid with diazomethane is a familiar example. The ionic pathway is especially likely when the intermediate carbocation would be stabilized. Thus, diazine (158) couples smoothly with phenols, presumably by thermal rearrangement to the corresponding diazo sugar, followed by acid-catalyzed N2 loss... 

Required Aniline hydrochloride, 4 g. aniiinc, 16 ml. diazo aminobenzene, 8 g. acetic acid, 20 ml. 

Add, with stirring, a solution of 6 8 g. of the fiis-diazo ketone in 100 ml. of warm dioxan to a suspension of 7 0 g. of freshly precipitated silver oxide in 250 ml. of water containing 11 g. of sodium thiosulphate at 75°. A brisk evolution of nitrogen occurs after 1 5 hours at 75°, filter the liquid from the black silver residue. Acidify the almost colourless filtrate with nitric acid and extract the gelatinous precipitate with ether. Evaporate the dried ethereal extract the residue of crude decane-1 10-dicarboxylic acid weighs 4 -5 g. and melts at 116-117°. RecrystaUisation from 20 per cent, aqueous acetic acid raises the m.p. to 127-128°. 

Alternatively, treat a solution of 3 9 g. of the 6is-diazo ketone in 50 ml. of warm dioxan with 15 ml. of 20 per cent, aqueous ammonia and 3 ml. of 10 per cent, aqueous silver nitrate under reflux in a 250 or 500 ml. flask on a water bath. Nitrogen is gently evolved for a few minutes, followed by a violent reaction and the production of a dark brown and opaque mixture. Continue the heating for 30 minutes on the water bath and filter hot the diamide of decane-1 lO dicarboxyhc acid is deposited on cooling. Filter this off and dry the yield is 3 -1 g., m.p. 182-184°, raised to 184-185° after recrystallisation from 25 per cent, aqueous acetic add. Hydrolyse the diamide (1 mol) by refluxing for 2-5 hours with 3N potassium hydroxide (4 mols) acidify and recrystaUise the acid from 20 per cent, acetic acid. The yield of decane-1 10-dicarboxyhc acid, m.p. 127-128°, is almost quantitative. 

The majority of preparative methods which have been used for obtaining cyclopropane derivatives involve carbene addition to an olefmic bond, if acetylenes are used in the reaction, cyclopropenes are obtained. Heteroatom-substituted or vinyl cydopropanes come from alkenyl bromides or enol acetates (A. de Meijere, 1979 E. J. Corey, 1975 B E. Wenkert, 1970 A). The carbenes needed for cyclopropane syntheses can be obtained in situ by a-elimination of hydrogen halides with strong bases (R. Kdstcr, 1971 E.J. Corey, 1975 B), by copper catalyzed decomposition of diazo compounds (E. Wenkert, 1970 A S.D. Burke, 1979 N.J. Turro, 1966), or by reductive elimination of iodine from gem-diiodides (J. Nishimura, 1969 D. Wen-disch, 1971 J.M. Denis, 1972 H.E. Simmons, 1973 C. Girard, 1974),... 

Phloroglucinol is Hsted in the Colourindex as Cl Developer 19. It is particularly valuable in the dyeing of acetate fiber but also has been used as a coupler for azoic colors in viscose, Odon, cotton (qv), rayon, or nylon fibers, or in union fabrics containing these fibers (157). For example, cellulose acetate fabric is treated with an aromatic amine such as (9-dianisidine or a disperse dye such as A-hydroxyphenylazo-2-naphthylamine and the amine diazotizes on the fiber the fabric is then rinsed, freed of excess nitrite, and the azo color is developed in a phloroglucinol bath at pH 5—7. Depending on the diazo precursor used, intense blue to jet-black shades can be obtained with excellent light-, bleach-, and mbfastness. 

Commercial Disperse Azo Dyes. The first proposal to use insoluble dyes in suspension in an aqueous foam bath, ie, disperse dyes, to dye cellulose acetate was in 1921 (60). Commercialization of disperse dyes began in 1924 with the introduction of the Duranol dyes by British Dyestuffs Corporation (61) and the SRA dyes by British Celanese Company (62). In contrast to the acid monoazo dyes, derivatives of benzene rather than of naphthalene are of the greatest importance as coupling components. Among these components mono- and dialkylariifines (especially A/-P-hydroxyethyl-and A/-(3-acetoxyethylanifine derivatives) are widely used couplers. Nitrodiazobenzenes are widely used as diazo components. A typical example is CeUiton Scarlet B [2872-52-8] (91) (Cl Disperse Red 1 Cl 11110). 

Azoic Dyes. These are used to produce cost-effective heavy yellow, orange, red, maroon, navy blue, brown, and black shades and are ptinted alongside other dye classes to extend the coloristic possibiUties for the designer. Two approaches are adopted. The common method ia the United States is to use both a naphthol derivative and a stabilized color base, usually in the form of a diazo imino compound in the same print paste. This mixture is soluble in dilute caustic soda and no coupling takes place at this stage. The dried prints are passed through steam at 100—105°C that contains acetic and/or formic acid vapor. As neutralization takes place on the print, the coupling occurs rapidly and the insoluble azoic dye is formed. 

A large number of pyridazines are synthetically available from [44-2] cycloaddition reactions. In one general method, azo or diazo compounds are used as dienophiles, and a second approach is based on the reaction between 1,2,4,5-tetrazines and various unsaturated compounds. The most useful azo dienophile is a dialkyl azodicarboxylate which reacts with appropriate dienes to give reduced pyridazines and cinnolines (Scheme 89). With highly substituted dienes the normal cycloaddition reaction is prevented, and, if the ethylenic group in styrenes is substituted with aryl groups, indoles are formed preferentially. The cycloadduct with 2,3-pentadienal acetal is a tetrahydropyridazine derivative which has been used for the preparation of 2,5-diamino-2,5-dideoxyribose (80LA1307). 

Thermal conversion of diazirines to linear diazo compounds was postulated occasionally and proved by indirect methods. The existence of a diazo compound isomeric to diazirine (197) was proved spectroscopically on short thermolysis in DMSO (76JA6416). An intermediate diazoalkane was trapped by reaction with acetic acid, yielding the ester (198) (77JCS(P2)1214). 

There are several examples of intramolecular reactions of monocyclic /3-lactams with carbenes or carbenoids most of these involve formation of olivanic acid or clavulanic acid derivatives. Thus treatment of the diazo compound (106) with rhodium(II) acetate in benzene under reflux gives (107), an intermediate in the synthesis of thienamycin (80H(14)1305, 80TL2783). 

Pyrido[],2-a]pyrimidine-3,7-dicarboxylate 396 was also obtained in the reaction of diazo compound 395 and methyl vinyl ketone in boiling benzene in the presence of a catalytic amount of ruthenium acetate. 

The diazo function in compound 4 can be regarded as a latent carbene. Transition metal catalyzed decomposition of a diazo keto ester, such as 4, could conceivably lead to the formation of an electron-deficient carbene (see intermediate 3) which could then insert into the proximal N-H bond. If successful, this attractive transition metal induced ring closure would accomplish the formation of the targeted carbapenem bicyclic nucleus. Support for this idea came from a model study12 in which the Merck group found that rhodi-um(n) acetate is particularly well suited as a catalyst for the carbe-noid-mediated cyclization of a diazo azetidinone closely related to 4. Indeed, when a solution of intermediate 4 in either benzene or toluene is heated to 80 °C in the presence of a catalytic amount of rhodium(n) acetate (substrate catalyst, ca. 1000 1), the processes... 

Intermediate 37 can be transformed into ( )-thienamycin [( )-1)] through a sequence of reactions nearly identical to that presented in Scheme 3 (see 22— 1). Thus, exposure of /(-keto ester 37 to tosyl azide and triethylamine results in the facile formation of pure, crystalline diazo keto ester 4 in 65 % yield from 36 (see Scheme 5). Rhodium(n) acetate catalyzed decomposition of 4, followed by intramolecular insertion of the resultant carbene 3 into the proximal N-H bond, affords [3.2.0] bicyclic keto ester 2. Without purification, 2 is converted into enol phosphate 42 and thence into vinyl sulfide 23 (76% yield from 4).18 Finally, catalytic hydrogenation of 23 proceeds smoothly (90%) to afford ( )-thienamycin... 

In the context of 12, the diazo keto function and the thiolactam are in proximity. This circumstance would seem to favor any process leading to the union of these two groupings. It is conceivable that decomposition of the diazo function in 12 with rhodium(n) acetate would furnish a transitory electron-deficient carbene which would be rapidly intercepted by the proximal thiolactam sulfur atom (see 20, Scheme 4). After spontaneous ring contraction of the... 

Ring enlargement via an insertion of a carbene generated in the a-position to the ring is an established method and has also been applied to the synthesis of oxepins. The ()3-allylpalladium chloride catalyzed decomposition of substituted ethyl diazo(4/7-pyran-4-yl)acetates in benzene at room temperature gives ethyl oxepin-4-carboxylates 1 in excellent yield.190 The ester function can be replaced by the phosphonate group and other P = 0-functions (see Houben-Weyl,... 

A solution of ethyl diazo(2,4,6-trimethyl-4//-pyran-4-yl)acetate (0.47 g, 2.0 mmol) in benzene (50 mL) was stirred with // -allylpalladium chloride dimer (15 mg) for 2h at rt, and then the solvent was evaporated. The residue was chromatographed (80-g basic alumina, EtOAc/hexane 1 2) yield 0.40 g (97 %) yellow oil. 

In 1949 Huisgen and Horeld produced evidence that the rate-limiting step of this phenylation is the isomerization of A-nitrosoacetanilide to the (covalent) diazo acetate (2.43). A decade later Suschitzky s group (Barben and Suschitzky, 1960 Miles and Suschitzky, 1962 Suschitzky, 1967) found that the diazo acetate dissociates into a diazonium-acetate ion pair (2.44). 

The ionization of (E)-diazo methyl ethers is catalyzed by the general acid mechanism, as shown by Broxton and Stray (1980, 1982) using acetic acid and six other aliphatic and aromatic carboxylic acids. The observation of general acid catalysis is evidence that proton transfer occurs in the rate-determining part of the reaction (Scheme 6-5). The Bronsted a value is 0.32, which indicates that in the transition state the proton is still closer to the carboxylic acid than to the oxygen atom of the methanol to be formed. If the benzene ring of the diazo ether (Ar in Scheme 6-5) contains a carboxy group in the 2-position, intramolecular acid catalysis is observed (Broxton and McLeish, 1983). 

Tezuka s group (Tezuka and Ando, 1985 Tezuka et al., 1986) was able to isolate and characterize the benzenediazo ether of 1-naphthol (6.10). They stirred a solid mixture of the molecular complex 6.9 formed between an a-azohydroperoxide acid and benzene with an excess of 1-naphthol at room temperature in the dark for several hours. The separation of this solid by thin layer chromatography (silica gel, with a benzene-ethyl acetate mixture [9 1] as eluent) afforded the diazo ether 6.10 as a yellow oil in 17 % yield, together with 4- and 2-phenylazo-l-naphthol (6.11 and 6.12, 4% and 42%, respectively), 4-phenylbenzaldehyde (32%), benzoic acid (23%), and traces of other compounds (Scheme 6-6). Higher yields of the diazo ether (up... 

The next intermediate, 5-diazo-6-methylene-l,3-cyclohexadiene (6.75) was postulated by Trondlin et al. (1978) because unsolvated ( naked ) acetate ions in benzene are strong proton acceptors. Experimental evidence for its role in this mechanism was given by these authors in two ways. 

If the diazonium acetate ion pair can lose a proton, it should also be possible to add a proton to the diazo-methylene compound 6.75. This hypothesis was checked experimentally by carrying out the indazole syntheses in the presence of D2S04. The result was not conclusive, as H/D exchange was observed to a small extent in two cases, but not in others. 

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