- Carbon-13 NMR Spectra of 1,3-Dioxolanes. I-New Parameters for cis- and trans-4-Methyl Groups in 2,4-Disubstituted Derivatives
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The 13C NMR spectra of 24 1,3-dioxolane derivatives are reported in an attempt to propose parameters for the C-2, C-4 and C-5 shifts from the 2-Me and 4-Me substituents, based on the ring stereochemistry.These parameters are obtained from simultaneuos equations, and clearly agree with those calculated by the use of pattern molecules.The calculated parameter for the C-4 shift due to a 2-Me group differs notably from that proposed by other workers.KEY WORDS 1,3-dioxolane derivatives 13C NMR Shift parameters
- Espinosa, Antonio,Gallo, Miguel A.,Campos, Joaquin,Entrena, Antonio,Camacho, Encarnacion
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- Aminopolycarboxylic acids and derivatives thereof
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There are provided chelating agents particularly useful for the preparation of diagnostic and therapeutic agents for magnetic resonance imaging, scintigraphy, ultrasound imaging, radiotherapy and heavy metal detoxification, said agents being compounds of formula I wherein n and m are 2, 3 or 4; and A, X, R1 and Z are as defined in the specification.
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- Novel pesticides, preparation and use
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The specification describes and claims methods of controlling acarine pests by application of a compound of Formula (I), methods of controlling arthropod pests by application of a compound of Formula (IA), compounds of Formula (IA) per se, pesticidal compositions comprising a compound of Formula (IA), and processes for preparing a compound of Formula (IA).
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- Synthesis and Use of 7-Substituted Norbornadienes for the Preparation of Prostaglandins and Prostanoids
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Syntheses of 7-substituted norbornadienes from 7-t-butoxy- and 7-halogeno-norbornadienes are described.Rearrangement of the products in the presence of peracetic acid gives bicyclic aldehydes (2) in equilibrium with enol ethers (3) which are hydrolysed to hydroxycyclopentenylacetaldehydes (4), and converted into key intermediates for the synthesis of prostaglandins and their analogues.Syntheses of prostaglandin J analogues with n-hexyl and phenyl groups replacing the ο-side-chain are described.
- Baxter, Anthony D.,Binns, Falmai,Javed, Tariq,Roberts, Stanley M.,Sadler, Peter,et al.
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p. 889 - 900
(2007/10/02)
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- Derivatives of C-6 functionalized 4-heteroalkanals. IV. Cyclic modifications in 6-hydroxy-4-oxa-alkanals
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The synthesis of 6-hydroxy-4-oxa-hexanal, 6-hydroxy-4-oxa-heptanal and some derivatives of them are described.It is shown by combined spectroscopic and kinetic methods how these hydroxyaldehydes do not respond to equilibrium processes characteristic of simple 6-hydroxy-aldehydes, since a slow isomerization to the respective 2-(2-hydroxyethyl)-1,3-dioxolanes are observed on standing in CDCl3 solutions, whilst an equilibrium between the hydroxyaldehydes and their corresponding cyclohemiacetal forms are observed in dioxane-water 3/1.
- Espinosa, Antonio,Gallo, Miguel A.,Campos, Joaquin
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p. 269 - 273
(2007/10/02)
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- Hydroboration. 57. Hydroboration with 9-Borabicyclononane of Alkenes Containing Representative Functional Groups
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The hydroboration of alkenes containing representative functional groups was examined with 9-borabicyclononane (9-BBN) in order to extend the hydroboration reaction for the preparation of functionally substituted organoboranes.Terminal alkenes containing a remote functional group are hydroborated with a remarkable regioselectivity (>=98percent terminal), producing the corresponding stable organoboranes. 9-BBN hydroborates the allylic derivatives so as to place boron essentially on the terminal carbon atom (>=97percent).The directive effect is further enhanced (>=99percent) in the case of β-methylallyl derivatives.The hydroboration of crotyl derivatives attaches boron predominantly at the 2-position, followed by an elimination-rehydroboration sequence.However, crotyl alcohol can be protected against elimination as the tert-butyl or tetrahydropyranyl ethers.The hydroboration-oxidation of ethyl crotonate involves a series of elimination, hydroboration, and condensation processes.In the vinyl, crotyl, and isobutenyl systems, the mesomeric effect of the substituent favors the placement of boron at the β-position, while the inductive effect favors the α-position, with the former effect predominating in most cases.Acyclic β-substituted organoboranes undergo rapid elimination.Nonpolar solvents and lower reaction temperatures decrease the rate of elimination.However, those derived from cyclic vinyl derivatives are relatively stable under neutral conditions, undergoing facile elimination in the presence of a base.
- Brown, Herbert C.,Chen, Jackson C.
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p. 3978 - 3988
(2007/10/02)
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