Benzocyclobutenone enolate: an anion with an antiaromatic resonance structure †

Broadus, Katherine M.; Kass, Steven R.

doi:10.1039/a905868k

Cited by 13 publications

(12 citation statements)

References 39 publications

(51 reference statements)

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“…During formation of carboxylated abamectin, 2 g pure abamectin was put into 100 ml of toluene, with the addition of 2 g NaH. The complexes were activated immediately by heating to 35 °C for 10 min, followed by filtering off the residue of the non‐reacted NaH in the system to gain the pure reactant (expected abamectin natrium salt) by vaporizing the residual toluene ( Broadus and Kass , 1999). Then, 1 g butyric anhydride was added to the system and fresh toluene was added again to a total volume of 100 ml for carboxylation.…”

Section: Methodsmentioning

confidence: 99%

Conjugation of δ‐endotoxin from Bacillus thuringiensis with abamectin of Streptomyces avermitilis as a new type of biocide, GCSC‐BtA, for control of agricultural insect pests

Liu

Şengonça

2003

Anz Schadlingskd

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Conjugation of d-endotoxin from Bacillus thuringiensis with abamectin, a toxin of Streptomyces avermitilis, was carried out to form a new type of biocide, GCSC-BtA based on ''Germany-China Scientific Cooperation'' research, for the control of agricultural insect pests. The strategy for biochemical linkage was designed by conjugating an amino group in B.t. protoxin with a carboxyl group in carboxylated abamectin under the treatment of conjugator EDC [1-Ethyl-3-(3-dimethylaminopropyl carbodiimide Hydrochloride)]. The formation of B.t. protoxin was processed by solubilizing B.t. crystal in 25 mM dithiothreitol (DTT) at 37°C for 2 h. The carboxylated abamectin was formed by carboxylating the NaH-activated abamectin with 10 mg/ml butyric anhydride at 111°C in a water-circumfluent condensation device for 2 h. The conjugating reaction, consisting of 5 mg/ml B.t. protoxin, 10 mg/ml carboxylated abamectin and 19.17 mg/ml EDC, was successfully conducted at room temperature for 24 h. Significant differences were found between pure abamectin, carboxylated abamectin and the conjugated BtA by means of UV-photo absorptions recorded at wavelengths 354, 438, 518, 600 nm (P < 0.01). LT 50 of the conjugated GCSC-BtA to the 3 rd instar larvae of Plutella xylostella (L.) (Lep., Plutellidae) was 35.27 lg a.i./ml, about 62 % and 76 % of that caused by the B.t. protoxin and the caxboxylated abamectin, respectively. The conjugated GCSC-BtA caused 87.14 % mortalities in larvae of P. xylostella, 93.75 % in adult Myzus persicae (Sulzer) (Hom., Aphididae) and 89.33 % in adult Phyllotreta vittata Fabricius (Col., Chrysomelidae) as compared to 48.33 % by the B.t. crystal only in P. xylostella. The symptoms caused by conjugated GCSC-BtA in the 3 rd instar of P. xylostella were black color in the head part and whiteyellow in the abdomen of dead larvae, which differed from the black color or the white-yellow all along the body caused by either the B.t. crystal or the abamectin, respectively. It was concluded that the conjugated GCSC-BtA biocide had a broader host spectrum and a faster killing speed than either the B.t. crystal or abamectin alone for the control of agricultural pests.B. Liu and C. Sengonca: Conjugation of Bacillus thuringiensis d-endotoxin with abamectin Anz. Schädlingskunde ⁄

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Section: Methodsmentioning

confidence: 99%

Conjugation of δ‐endotoxin from Bacillus thuringiensis with abamectin of Streptomyces avermitilis as a new type of biocide, GCSC‐BtA, for control of agricultural insect pests

Liu

Şengonça

2003

Anz Schadlingskd

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“…Our interest in the effects of ring strain on the reactivity of the α-protons in cyclic carbonyl systems stems from studies involving benzocyclobutenone ( 2 ). The α-protons of 2 were found , to be much less reactive than compounds with similar structure 5c. The lack of reactivity observed in 2 was rationalized on the basis of the generation of a carbanion wherein formation of the enolate increases the ring strain in the carbocycle and creates an antiaromatic π-system 5c.…”

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confidence: 98%

Ring Strain and Its Effect on the Rate of the General-Base Catalyzed Enolization of Cyclobutanone

2002

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[reaction: see text] The 3-quinuclidinone-catalyzed (pK(BH) = 7.5) enolization of cyclobutanone (1) in D(2)O at 25 degrees C, I = 1.0 (KCl) was followed by deuterium incorporation, which was determined by (1)H NMR. The second-order rate constant for the buffer-catalyzed deprotonation of 1 was found to be k(B) = 3.3 x 10(-4) M(-1) s(-1), which is compared to rates for acetone and 2-(2'-oxopropyl)benzaldehyde under similar conditions. The data shows that ring strain has very little effect on the energy barrier to deprotonation of 1 vs the unstrained systems.

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“…Evidence for the generation of the enolate of benzocyclobutenone has come about through the generation of dimer 2 (Scheme ) which was rationalized on the basis of initial enolate addition to another benzocyclobutenone molecule and subsequent rearrangement of the initially formed aldol product 4b. Direct evidence for the formation of the enolate has been reported for the reaction of 2-methylbenzocyclobutenone, where the aldol product has been isolated, and for the reaction of benzocyclobutenone, where the enolate was trapped with chlorotrimethylsilane . In both cases, the carbanion was generated in THF at −78 °C, using lithium tetramethylpiperidide.…”

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confidence: 99%

The Reversible Formation of the Enolate of Benzocyclobutenone under Aqueous Conditions

2001

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Benzocyclobutenone enolate: an anion with an antiaromatic resonance structure †

Cited by 13 publications

References 39 publications

Conjugation of δ‐endotoxin from Bacillus thuringiensis with abamectin of Streptomyces avermitilis as a new type of biocide, GCSC‐BtA, for control of agricultural insect pests

Conjugation of δ‐endotoxin from Bacillus thuringiensis with abamectin of Streptomyces avermitilis as a new type of biocide, GCSC‐BtA, for control of agricultural insect pests

Ring Strain and Its Effect on the Rate of the General-Base Catalyzed Enolization of Cyclobutanone

The Reversible Formation of the Enolate of Benzocyclobutenone under Aqueous Conditions

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