Zinc-mediated ring-expansion and chain-extension reactions of beta-keto esters

[Chemical reaction: see text] The reaction of cyclic beta-keto esters with CF3CO2ZnCH2I provided the corresponding ring-expanded products in moderate to good yields. Although alpha-substituted acyclic beta-keto esters reacted with much less efficient, chain-extension reaction of simple beta-keto esters also proceeded effectively to generate gamma-keto esters in high yields.     

Enantioselective chlorination and fluorination of beta-keto phosphonates catalyzed by chiral Lewis acids

The direct chiral Lewis acidic enantioselective chlorination and fluorination of beta-keto phosphonates is presented; the chlorination proceeds in high yields and with up to 94% ee using NCS as the chloro source, while the fluorination with (PhSO2)2NF (NFSI) gives the optically active alpha-fluoro-beta-keto phosphonates in moderate to good yields and with up to 91% ee.     

Zinc-mediated chain extension reaction of 1,3-diketones to 1,4-diketones and diastereoselective synthesis of trans-1,2-disubstituted cyclopropanols

[reaction: see text] A variety of 1,3-diketones can be efficiently converted into the corresponding 1,4-diketones and trans-1,2-disubstituted cyclopropanols by using organozinc species in one-pot reactions. It was found that 2.3 equiv of CF3CO2ZnCH2I was effective to give the corresponding chain-extended products in 44-85% yields, while a mixture of organozinc species formed from 4.0 equiv of Et2Zn, 2.0 equiv of CF3CO2H, and 4.0 equiv of CH2I2 resulted in the formation of trans-1,2-disubstituted cyclopropanols with quite good yields and diastereoselectivity.     

Catalytic enantioselective fluorination and amination of beta-keto phosphonates catalyzed by chiral palladium complexes

[reaction: see text] The catalytic enantioselective fluorination and amination of beta-keto phosphonates catalyzed by chiral palladium complexes is described. Treatment of beta-keto phosphonates with N-fluorobenzenesulfonimide (NFSI) as electrophilic fluorinating reagent and diethyl azodicarboxylate (DEAD) as electrophilic amination reagent under mild reaction conditions afforded the corresponding alpha-substituted beta-keto phosphonates in moderate to excellent yields with excellent enantiomeric excesses.     

Catalytic asymmetric addition of beta-keto phosphonates to an activated imine--formation of optically active functionalized phosphonate alpha-amino acid derivatives

The direct stereoselective addition of an activated imine to beta-keto phosphonates in the presence of chiral Lewis acid complexes is developed. The evaluation of different activated imines shows that an N-tosyl-alpha-imino ester adds in a diastereo- and enantioselective fashion to beta-keto phosphonates activated by especially chiral copper(II)-bisoxazoline complexes. An evaluation of Lewis acids, chiral ligands and reaction conditions, such as solvent, bases and other additives, shows that high yields, moderate diastereoselectivity and good enantioselectivity are obtained. The scope of the reaction is demonstrated for the reaction of beta-keto phosphonates and finally, the mechanism for the catalytic stereoselective step is presented.     

Zinc-mediated allylation of aldoxime esters

A facile zinc-mediated Barbier-type allylation of aromatic aldoxime esters, producing the corresponding protected homoallylic hydroxylamines, which are readily converted into homoallylic hydroxamic acids, is described.     

Facile and efficient one-pot synthesis of highly functionalized thieno[2,3-b]thiopyran-4-ones from beta-keto epsilon-xanthyl phosphonates

The one-pot synthesis of various functionalized thieno[2,3- b]thiopyran-4-ones from readily available beta-keto epsilon-xanthyl phosphonates has been accomplished by combining a Horner-Wadsworth-Emmons olefination with a base-induced intramolecular domino cyclization/thio-Michael addition. The use of cyclic ketones in this transformation allowed a facile access to novel spiro-type thieno[2,3- b]thiopyran structures.     

Diels-Alder chemistry of 2-diethoxyphosphinylcyclohex-2-enones. A new approach to complex phosphonates and synthetic applications of the beta-keto phosphonate system

Enone phosphonates 1 and 2 were found to be excellent dienophiles for the Diels-Alder reaction, giving phosphonate-containing polycycles, and the phosphonate group of the resulting adducts facilitated both the installation of an angular alkyl group via a reductive alkylation process and the regioselective generation of a ring junction double bond via an intramolecular Wadsworth-Horner-Emmons reaction.     

Asymmetric synthesis of ring functionalized trans-2,6-disubstituted piperidines from N-sulfinyl delta-amino beta-keto phosphonates. total synthesis of (-)-myrtine

Sulfinimine-derived N-sulfinyl delta-amino beta-ketophosphonates are transformed via the enaminones to the phosphoryl dihydropyridones that selectively give trans-2,6-disubstituted 1,2,5,6-tetrahydropyridines on organocuprate addition and dephosphorylation.     

Zinc-mediated asymmetric epoxidation of nitro alkenes with oxygen

The asymmetric epoxidation of nitro alkenes using oxygen in the presence of diethylzinc and N-methyl pseudo-ephedrine as a chiral additive is reported. This method provides an access to 3-substituted trans-2-nitro oxiranes of excellent diastereomeric purity (de≥98%) and with medium to good enantiomeric excesses (ee=36–82%).     

Europium phosphonates

Conditions for the preparation and pyrolysis of europium nitrilotrimethylphosphonate and ethylenediaminetetramethylphosphonates were studied.     

Furoyl phosphonates

A series of furoyl phosphonates bearing methyl, methoxymethyl, and diethoxyphosphorylmethyl groups in the furan ring have been synthesized via the Arbuzov reaction from the corresponding acid chlorides. NMR spectral parameters of the prepared compounds were studied. The values of coupling constants between the phosphorus nuclei and the carbon nuclei of the furan ring have been examined with relation to the location of the acylphosphoryl group in the furan ring, the nature of second substituent, and location of the latter with respect to the phosphorus-containing substituent in the furan ring. The substitution in position 4 of the furan ring of 3-furoyl phosphonates has been shown to strongly decrease the value of the coupling constant between the phosphorus nucleus and the C² atom of the heterocycle. The interaction between the phosphorus nuclei has not been detected in the spectra of the compounds containing both diethoxyphosphorylmethyl and acylphosphonate fragments.     

Molecular transition-metal phosphonates

Molecular transition-metal phosphonates are of relatively recent origin and can be assembled by several synthetic strategies. The nuclearity and the structure of the metal aggregates can be modulated by several factors including the stoichiometry of the reactants, nature of the metal precursor and the type of phosphonic acid used. This perspective summarizes some of the recent work carried out on copper(II)-, zinc(II)- and cadmium(II) phosphonates with particular emphasis on their synthesis and structure.     

Hetero Diels-Alder reactions of acyl phosphonates: synthesis of glycosyl type phosphonates

We have prepared glycosyl type phosphonates via hetero Diels-Alder (HDA) reactions of acyl phosphonates with electron rich dienes. HDA reactions of acyl phosphonates with Danishefsky’s diene required thermal activation to yield the desired dihydropyranones in good yield (70-91%). The reactions with Brassard’s diene involved Lewis acid promotion to yield the corresponding lactones, though in moderate yield (33-69%).     

Free radical ring expansion and chain extension of 1,3-diketones

Free radical-promoted one carbon ring expansion and chain extension of 1,3-diketones including 1,3-diarylpropane-1,3-diones and 2-aroyl-3,4-dihydro-2H-naphalen-1-one to generate corresponding 1,4-diketones are described.     

Zinc-mediated reactions on salicylaldehyde for Botrytis cinerea control

Botrytis cinerea is a necrotrophic fungusth at a ffects various plant species.Chemical control is an ecessity and as much as possible,eco-friendly conditions and bioresources to obtain these chemicals should be used.In this context,a series of products w as obtained from salicylaldehyde using zinc as a powerful reagent and tested for antifungal activity against Botrytis cinerea.     

Stereocontrolled formation of ketomethylene isosteres through tandem chain extension reactions

A zinc-mediated chain extension reaction is the key step in the preparation of gamma-keto amides derived from amino acids. The use of tandem reaction sequences, in which the intermediate zinc enolate is trapped with electrophilic reagents, results in the incorporation of alpha-substituents, which mimic the side chains found in natural amino acid systems. Use of the chiral amino acid L-proline as a stereo-directing element provides a diastereoselective route to various ketomethylene isosteres.     

Aminobromination of unsaturated phosphonates

Unexpected syn beta-amino-alpha-bromination of unsaturated phosphonates was observed under typical Sharpless AA reaction conditions with excess N-bromoacetamide.