Ethoxycarbonyl Substituents Research Articles

Systemic Fungicides. The Synthesis of Pyrazolo[1,5-a]pyrimidine Analogues of Carboxin

The synthesis of a series of pyrazolo [1,5-a] pyrimidine derivatives, structural analogues of the systemic fungicide carboxin, is described. A common intermediate incorporating structural features desirable for fungicidal activity, N-phenyl-3(5)-amino-5(3)-methylpyrazole-4- carboxamide (6), was used to prepare pyrazolo [1,5-a] pyrimidines variously substituted in positions 5 and 7 of the ring system. Bromination of N-phenyl-2-methylpyrazolo[1,5-a]pyrimidine-3-carboxamide (8) occurred preferentially in the phenyl ring and the 6-bromo derivative was prepared by bromination of the corresponding 3-ethoxycarbonyl derivative (24). Attempted nitration of the ester (24) resulted in displacement of the ethoxycarbonyl substituent by a nitro group. The simplest pyrazolo [1,5-a] pyrimidine (8) showed a high level of fungicidal acitvity in fungal growth assays of Basidiomycete species, but compounds substituted in the pyrimidine ring were inactive.

Le cation méthylènecyclopropyle: Etude théorique. Solvolyse des halogénocyclopropènes et des halogénométhylenecyclopropanes

The solvolysis in acid solution of allylic halides and acetates of methylenecyclopropanes and cyclopropylmethanes does not lead to ring opening when there is an ethoxycarbonyl substituent on the ring methylene. Only the cyclopropenyl derivative is obtained. A study of the electronic structure and the geometry of the possible allylic cation intermediate has been carried out using the MNDO method. In addition, the influence of the substituents on the ring opening of this cation has beeen examined. It appears that the ring opening is disfavoured upon substitution of an alkyl group by alkoxymethyl on the ring methylene group.

Synthesis and fragmentation-condensation reaction of 1,3-diethoxycarbonylallylidenetriphenylphosphononium ylide

Alkylidenephosphonium ylides with ethoxycarbonyl substituents in the α-position fragment in a retro -Michael fashion during condensation with aldehydes.

Cis- and trans-Azetidin-2-ones from nitrones and copper acetylide

The reaction between nitrones and copper acetylides in pyridine yields cis- and trans-azetidinones. Deuteriation and isomerisation studies indicate that the trans-compound is produced from the initially formed cis-isomer and that the amount of cis-product may be increased by using non-basic solvents. Lactams with aromatic, aliphatic, and ethoxycarbonyl substituents may be obtained from appropriately substituted acetylenes, and the use of cyclic nitrones leads to bicyclic compounds.

Mass spectra of porphyrins with ethoxycarbonyl substituents

The mass spectra of porphyrins with ethoxycarbonyl substituents in the Β positions were obtained. It was observed that the chief paths for fragmentation of the porphyrins are common to all of them, regardless of the number of ethoxycarbonyl groups.

Electronic spectra of copper and zinc complexes of porphyrins containing ethoxycarbonyl substituents

Copper and zinc complexes of porphyrins containing ethoxycarbonyl substituents have been synthesized and their absorption spectra in the visible region have been studied. A connection has been shown between the α/β ratio of the absorption bands and the order of substitution of electronegative groups in the porphyrins.

Electronic structure of porphyrins with electronegative substituents

Using the MO LCAO method in Huckel's approximation, the π-electronic charges and the bond orders of porphyrins containing ethoxycarbonyl and methyl substituents in the β-positions have been calculated. A correlation has been observed between the frequencies of stretching vibrations of the C=O groups in the IR spectra and the orders of their bonds. Changes in the chemical shifts of the protons of the methyl groups with the introduction of ethoxycarbonyl substituents agree with the changes in the π-electron charges.

Influence of ?-electronic charges on the chemical shifts of the meso-protons in ?-ethoxycarbonyl-substituted porphyrins

A calculation has been made of the influence of the electric field of π-electronic charges on the chemical shifts of the meso-protons in β-ethoxycarbonyl-substituted porphyrins. A comparison of the calculated and experimental figures shows that the change in the chemical shifts taking place with the introduction of ethoxycarbonyl substituents into the β-position is due mainly to the changes in the π-electronic charges.

Influence of electronegative substituents on the electronic spectra of the porphyrins in the form of dications

The positions of the electronic absorption bands and also the intensities of the Soret bands of the porphyrins with ethoxycarbonyl substituents in the form of dications have been calculated by the LCAO MO method in Huckel's approximation. Comparison with the experimental results shows good agreement.

Studies of the relationship between chemical structure and porphyria-inducing activity—III

A series of analogues of 3,5-diethoxycarbonyl-2,4,6-trimethylpyridine has been prepared and tested for porphyria-inducing activity in chick embryo liver cells. These studies show that the critical feature for activity in these compounds is an ethoxycarbonyl substituent in a pyridine, dihydropyridine, or benzene ring with two ortho-alkyl substitueras. The porphyria-inducing activity detected in 2,4,6-trimethylbenzamide suggests a relationship between this group of compounds and those of the allylisopropylacetamide group.

Studies of the relationship between chemical structure and porphyria-inducing activity

A porphyria, induced in guinea pigs by means of 3,5-diethoxycarbonyl-l,4-dihydro-2,4,6-trimethylpyridine (DDC) is known to be the result of an enhanced synthesis of the enzyme, δ-aminolaevulic acid synthetase in liver cells. To further examine this phenomenon several analogues of DDC (Ib) and the corresponding pyridine (lIb) have been prepared and tested for porphyria-inducing activity. A study of the Fisher-Hirsch-felder-Taylor models and the u.v. absorption spectra of these analogues indicated that the 2-, 4-, and 6-methyl substituents cause a twisting of the 3- and 5-ethoxycarbonyl substituents out of the plane of the ring. The nonplanar relationship between the ethoxycarbonyl substituents and the ring appears to be necessary for optimal porphyriainducing activity

904. Terpene synthesis. Part II. A stereoselective alkylation induced by an ethoxycarbonyl substituent

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