Synthesis monosubstituted

The monosubstituted malonic ester still possesses an activated hydrogen atom in its CH group it can be converted into a sodio derivative (the anion is likewise mesomeric) and this caused to react with an alkyl halide to give a C-disubstituted malonic ester. The procedure may accordingly be employed for the synthesis of dialkyImalonic and dialkylacetic acids ... 

As compared to vitamin K, vitamin K2 is relatively unimportant industrially with only a few producers, such as Teikoku Kagaku Sangyo and Eisai, and is dominated by the manufacture of vitamin K2 20) industrial synthesis parallels that of vitamin and involves as a key step alkylation of monosubstituted menadione with an appropriate (all-E) reagent (44,45). Several academic syntheses have been described (46—49). 

Furazano[3,4-/]quinoxaline, 7,8-diphenyl-synthesis, 6, 412 Furazanothiophene synthesis, 6, 417 Furazans, 6, 393-426 biological activity, 6, 425 bond angles, 6, 396 bond lengths, 6, 396 coordination compounds, 6, 403 diamagnetic susceptibilities, 6, 395 dipole moments, 6, 395, 400 heats of combustion, 6, 400 heterocyclic ring reactions, 6, 400-403 IR spectra, 6, 398 isoxazoles from, 6, 81 mass spectra, 6, 399 microwave spectroscopy, 6, 395, 396 MO calculations, 6, 395 monosubstituted... 

The use of 2,5-dimethoxytetrahydrofuran (20) as a succinaldehyde equivalent has expanded the PK synthesis to include unsubstituted pyrroles, for example, 21. A novel synthesis of monosubstituted succinaldehydes is also available for the PK pyrrole synthesis. ... 

Although nearly all Paal-Knorr condensations produce di-, tri-, or tetrasubstituted furans, it is possible to use this reaction to generate monosubstituted furans. Molander demonstrated the utility of this method with his synthesis of 2-(methyldiphenylsilyl)furan (11) from dicarbonyl 10. ... 

The discovery of junipal focused the attention of Sorensen, who had been investigating the occurrence of polyacetylenes in Com-positae, on the possibility that these acetylenes were accompanied by thiophenes. From Coreopsis grandiflora Hogg ex sweet, 2-phenyl 5-(1-propynyl) thiophene (240) was isolated and its structure confirmed by synthesis of the tetrahydro compound, 2-phenyl-5-n-propyl-thiophene. From the root of tansy, the cis and trans isomers of methyl 5-(l-propynyl)-2-thienylacrylate (241) have been isolated. The total synthesis of trans (241) was achieved by reacting junipal with methylcarbethoxy triphenylphosphonium bromide (Wittig reaction) Several monosubstituted thiophenes, (242), (243), and... 

A new general synthesis of 3-substituted derivatives has been reported (99MC13) (Scheme 9). Thus, the nitro group of furoxan 27 underwent a facile hydride replacement on treatment with NaBH4 in EtOH to give 3-monosubstituted furoxans 23. The result of this reaction is independent of the nature of R. 

The reaction of diacetylene or its monosubstituted homologs with guanidine in the presence of an equimolar amount of sodium ethylate (80°C, EtOH, 14 h) leads to 2-amino-4-alkylpyrimidines (33) (70ZOR1347 71ZOR14). Their structures were proved by comparison of their properties (as well as those of their picrates) with those of authentic samples obtained by independent synthesis. 

The reaction of 4-diethylaminobut-3-en-2-one with monosubstituted hydrazines (95°C, H+, MeOH, HjO, 10 h) leads to pyrazoles 261 and 263 (yield 54%) at a ratio depending on the acidity of the medium. In an acidic medium the isomers 263 are predominantly obtained (76ZOR2063). Aminobutenones with hydrazine give only 5-methylpyrazoles (263) (69ZOR223). Enhydrazones 260 and 262 appear to be the synthesis intermediates. 

The hindered carbon-centered radicals are most suited as mediators in the polymerization of 1,1-disubstituled monomers e.g. MMA,78,95 other methacrylates and MAA,06 and AMS97). Polymerizations of monosubstituted monomers are not thought to be living. Dead end polymerization is observed with S at polymerization temperatures <100°C.98 Monosubstituted monomers may be used in the second stage of AB block copolymer synthesis (formation of the B block).95 However the non-living nature of the polymerization limits the length of the B block that can be formed. Low dispersities are generally not achieved. 

The reaction also proceeds readily with A/-monosubstituted 1,2-diaminobenzenes (6.45, R = alkyl, aryl, acyl). Kroupa and Matrka (1970) investigated optimal reaction conditions for the synthesis of 1,2,3-benzotriazole from 1,2-diaminobenzene. 

Does this model give us a practical solution for the synthesis of monosubstitution products in high yields The model teaches us that reactions are not disguised by micromixing if the intrinsic rate constant (in Scheme 12-84 k2o and k2v>) is significantly less than 1 m-1s-1. As discussed in Section 12.7, the intrinsic rate constant refers to unit concentrations of the acid-base equilibrium species involved in the substitution proper, not to analytical concentrations. Therefore, if the azo coupling reaction mentioned above is not carried out within the range of maximal measured rates (i.e., with the equilibria not on the side of the 1-naphthoxide ion and... 

Of perhaps greater use for organic synthesis was the observation that photo-driven reactions of alkoxycarbenes with unsubstituted optically active ene carbamates [65] produced aminocyclobutanones in fair yield with high dia-stereoselectivity (Table 12) [66]. In contrast, with a gem-disubstituted ene carbamate, the syn-anti selectivity was low but high asymmetric induction a to nitrogen was observed (Eq. 16). Trans-monosubstituted ene carbamates failed to react, as did a,/J-unsaturated chromium carbene complexes. 

Some advances have been made in the Paal-Knorr synthesis of pyrroles by the condensation of primary amines with 1,4-dicarbonyl species. For instance, a new synthetic route to monosubstituted succinaldehydes allows for the facile preparation of 3-substituted pyrroles <96TL4099>. Additionally, a general method for the synthesis of 1-aminopyiroles has been devised by the condensation of commercially available 2,2,2-trichloroethyl- or 2-(tri-methylsilyl)ethylhydrazine with 1,4-dicarbonyl compounds <96JOCl 180>. A related route to such compounds involves the reaction of a-halohydrazones with p-dicarbonyl compounds <96H(43)1447>. Finally, hexamethyldisilazane (HMDS) can be utilized as the amine component in the Paal-Knorr synthesis in the presence of alumina, and this modification has been employed in the synthesis of tm azaprostacyclin analog <96S1336>. 

With a-monosubstituted ylides the oxidation results in the formation of alkenes (by subsequent Wittig reaction on the intermediate aldehyde). A recent example of such synthesis is found in the preparation of all-(Z)-cyclododecate-traene by oxidation of the appropriate bis-ylide [33]. It must be pointed out that an approach of the same macrocycle based on ring closing metathesis was found ineffective. 

The enzymatic polymerization of 12-hydroxydodecanoic acid in the presence of 11-methacryloylaminoundecanoic acid conveniently produced the methacrylamide-type polyester macromonomer. Lipases CA and CC were active for the macromonomer synthesis. Enzymatic selective monosubstitution of a hydroxy-functional dendrimer was demonstrated. Lipase CA-catalyzed polymerization of 8-CL in the presence of the first generation dendrimer gave the poly(8-CL)-monosubstituted dendrimer. 

In basic aqueous media, a kinetic study of the reaction between stannate(II) ions and alkyl halide shows that mono- and disubstituted organotin compounds are formed (Eq. 6.12a).27 The monosubstituted organotin compound is obtained after a nucleophilic substitution catalyzed by a complexation between the tin(II) and the halide atom. The disubstituted compound results from an electrophilic substitution coupled with a redox reaction on a complex between the monosubstituted organotin compound and the stannate(II) ion. Stannate(IV) ions prevent the synthesis of the disubstituted compound by complexation. Similarly, when allyl bromide and tin were stirred in D2O at 60° C, allyltin(II) bromide was formed first. This was followed by further reaction with another molecule of allyl bromide to give diallyltin(IV) dibromide (Eq. 6.12b).28... 

In addition to these monostannylene complexes, distannylene-metal complexes have also been prepared, either in competition with monosubstituted species (Eq. (21)) or by direct synthesis (Eq. (22)). 

Fig. 11. Enzymatic synthesis of poly( -CL) monosubstituted first generation dendrimer...

Hydrazones are also useful substrates in the preparation of pyrazoles. Reaction of N-monosubstituted hydrazones with nitroolefins led to a regioselective synthesis of substituted pyrazoles <060L3505>. lf/-3-Ferrocenyl-l-phenylpyrazole-4-carboxaldehyde was achieved by condensation of acetylferrocene with phenylhydrazine followed by intramolecular cyclization of the hydrazone obtained under Vilsmeier-Haack conditions <06SL2581>. A one-pot synthesis of oxime derivatives of l-phenyl-3-arylpyrazole-4-carboxaldehydes has been accomplished by the Vilsmeier-Haack reaction of acetophenone phenylhydrazones <06SC3479>. 

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