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Diazo-acetic ester

Diazo-acetic Esters. —Mercuric oxide dissolves in the cooled ethyl ester of diazo-acetic acid, and the product is extracted with ether. From the ethereal solution yellow, rhombic crystals of mercury bis-diazo-aceiic ethyl ester are deposited, the parameters of which are a b c=0-4546 1 0-72527. The crystals melt with decomposition at 104° C., and are affected by direct sunlight, mercury separating out. The substance explodes on concussion and is volatile in steam, with some decomposition. [Pg.65]

The reverse trend was found for intramolecular cyclopropanation of a-(alkenyloxysilyl)diazo-acetic esters. For the synthesis of methyl 2,2-diisopropyl-3-oxa-2-silabicyclo[4.1.0]heptane-l-carboxylate (7) from methyl diazo[(but-3-enyloxy)diisopropylsilyl]acetate, the thermal procedure gave the best result. In contrast, the lower homologs, 3-oxo-2-silabicyclo[3.1.0]hexanes, were only obtained by photochemical or catalytic decomposition of the corresponding diazo esters (see also Section 1.2.1.10.). [Pg.429]

Copper powder, copper bronze, Cu O, CuO, CuSO, CuCl and CuBr were the first catalysts which were used routinely for cyclopropanation of olefins as well as of aromatic and heteroaromatic compounds with diazoketones and diazoacetates. Competing insertion of a ketocarbene unit into a C—H bond of the substrate or solvent remained an excpetion in contrast to the much more frequent intramolecular C—H insertion reactions of appropriately substituted a-diazoketones or diazoacetates Reviews dealing with the cyclopropanation chemistry of diazo-acetic esters (including consideration of the efficiency of the copper catalysts mentioned above) and diazomalonic esters as well as with intramolecular cyclopropanation reactions of diazoketones have appeared. [Pg.85]

The rhodium- or copper-catalyzed cyclopropanation of furan and its derivatives with diazo-acetic esters,300-302 or ethyl 2-diazopropanoate300 usually leads to a mixture of the 2-oxa-bicyclo[3.1.0]hex-3-ene-e co-6-carboxylate, ring-opened (4Z)-6-oxohexa-2,4-dienoates, and ring-substituted furans. Only with electron-deficient furans methyl furan-2-carboxylates, 2-[( )-2-methoxycarbonylvinyl]furan300 and with benzofuran,301,303 was the cyclopropane product obtained exclusively. Examples 37-40 are representative.300... [Pg.482]

The synthesis of cllastatin constitutes one of the first enantioselective syntheses on an Industrial scale. In 1966, H. NozakI and R. Noyorl Investigated the enantioselective [2 -I-1 ]-cycloaddition of diazo-acetic esters to olefins. From this, Sumitomo developed industrial processes for the preparation of pyrethroids and cilastatin. In the key step, ethyl diazoacetate is decomposed in presence of isobutene at a dimeric, enantio-merically pure copper complex. The resulting ethyl di-methylcyclopropanecarboxyl-ate has an optical purity of 92% ee. [Pg.252]

The addition of 2-diazopropane or 3-diazopentane to (112) results in exo-endo mixtures of both the triazoline (113) and the bicyclo[2.1,0]pentane (114). However, with the 1,2,3,4-tetramethyl analogue of (112) no addition occurs, Surprisingly, the imide (115) incorporates two and three molar equivalents of methylene from diazomethane to give products of spirocyclopropanation at C-4. Monocyclopropana-tion of (116) at the least substituted double bond proceeds efficiently when diazo-acetic ester decomposition is catalysed by copperfn) and similar monoaddition to... [Pg.31]

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... [Pg.254]

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... [Pg.262]

ETHYL DIAZOACETATE (Acetic acid, diazo-, ethyl ester)... [Pg.29]

Copper(ll) acetylacetonate Copper, bis(2,4-pentanedionato-0,0 )- (9) (46369-53-3) Methyl diazoacetate Acetic acid, diazo-, methyl ester (8,9) (6832-16-2) Triethylammonium fluoride Triethylamine hydrofluoride (8) Elhanamine, N,N-diethyl-, hydrofluoride (9) (29585-72-6)... [Pg.236]

One of the earliest uses for rhodium(II)-catalyzed dipoles was demonstrated in Davies furan synthesis [22]. Isomiinchnones were also shown to produce substituted furans [115]. Additional furan syntheses have been described using silylacetates [116], unsaturated esters [117], and fluoroalkyl diazo acetates [118]. The synthesis of furofuranones and indenofuranones 35 from a-diazo ketones having pendant alkynes has also been reported (Eq. 6) [119]. Other fused heterocyclic systems include furo[3,4-c]furans [120, 121] furo[2,3-b]furans [122] as well as thiobenzofurans [123], and benzoxazoles[124] have also been synthesized with this methodology. [Pg.441]

SYNS AZASERIN 1-AZASERINE AZS CI-337 CL 337 CN-15,757 DIAZOACETATE (ESTER)-1-SERINE 1-DIAZOACETATE (ESTER) SERINE DIAZO-ACETIC ACID ESTER with SERINE o-DIAZOACETYL-l-SERINE NSC-742 P-165 RCRA WASTE NUMBER U015 1-SERINE DIAZOACETATE 1-SERINE DIAZOACETATE (ester)... [Pg.118]

DIAZOACETATE (ESTER) SERINE see ASA500 DIAZO-ACETIC ACID ESTER with SERINE see ASA500 DIAZOACETIC ACID, ETHYL ESTER see DCN800 DIAZOACETIC ESTER see DCN800 N-DIAZOACETILGLICINA-IDRAZIDE (ITALIAN) see DC0800... [Pg.1613]

The requisite a-diazo thiol esters are conveniently prepared by using the "detrifluoroacetylative" diazo transfer strategy previously developed in our laboratory. Cycloadditions are best carried out by using as little as 0.006 equiv of rhodium(II) acetate to promote the thia-Wolff rearrangement. Reactions involving the more nucleophilic ketenophiles proceed smoothly in refluxing dichloromethane (40°C), while cycloadditions with less reactive partners are best accomplished in 1,2-dichloroethane (83°C). As is standard for ketene cycloadditions, the optimal protocol involves slowly adding a solution of the diazo thiol ester to a solution of the ketenophile and catalyst in order to minimize competitive ketene dimerization. [Pg.75]

Photolytic and catalytic decomposition of a-diazo esters produces )8-lactones, which are formed via intramolecular C—H insertion of a carbene or carbenoids. Tertiary alkyl esters of diazomalonic acid are decomposed by rhodium acetate with exclusive formation of the four-membered ring 211. This suggests a smooth insertion into the C—H bond activated by the adjacent oxygen atom (90TL1023). jS-Lactone 212 was obtained by photolysis of diazo malonic ester 213 (71CC577). [Pg.136]

Under the conditions of homogeneous catalysis, decomposition temperatures are normally significantly lower than with the heterogeneous catalysts mentioned above, and cyclopropane yields in general are higher. However, catalysts of type 2 must first be converted into the active form [presumably a copper(I) monochelate] by brief heating or by in situ reduction (see Table 10). Another soluble catalyst, copper(I) triflate, even decomposes diazoacetic esters and diazomalonic esters at temperatures below 0 °C and sterically more encumbered diazocarbonyl compounds (e.g. a-diazo-a-trialkylsilyl acetic esters " ) still at room temperature, and has shown its effectiveness in a number of cyclopropanation reactions. Since copper(I) triflate is... [Pg.445]


See other pages where Diazo-acetic ester is mentioned: [Pg.338]    [Pg.393]    [Pg.345]    [Pg.348]    [Pg.333]    [Pg.338]    [Pg.393]    [Pg.345]    [Pg.348]    [Pg.333]    [Pg.25]    [Pg.392]    [Pg.171]    [Pg.14]    [Pg.197]    [Pg.1138]    [Pg.784]    [Pg.313]    [Pg.337]    [Pg.784]    [Pg.76]    [Pg.115]    [Pg.26]    [Pg.510]    [Pg.75]    [Pg.197]    [Pg.216]    [Pg.224]    [Pg.432]    [Pg.329]   
See also in sourсe #XX -- [ Pg.475 ]




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