Zinc-Mediated Allylation Research Articles

One-Pot Synthesis of Aza-Morita-Baylis-Hillman Adducts via Zinc-Mediated Allylation of 4-Bromocrotonates and Imines.

An approach to the synthetically valuable β-substituted aza-Morita-Baylis-Hillman (MBH) type products, through zinc-mediated allylation of imines with 4-bromocrotonates followed by subsequent isomerization of the double bond, was developed. Complementary to classical MBH reaction, this reaction utilizes easily available 4-bromocrotonates as the reaction partners, providing a rapid alternative to the traditional use of α,β-unsaturated carbonyl compounds. The short reaction time, one-pot operation, broad substrate scopes, gram-scale synthesis, and synthetic application exemplified the utility and practicability of this method.

Aqueous single step synthesis and structural characterization of allylated, propargylated, and benzylated 3-substituted 3-aminooxindoles

ABSTRACTEfficient zinc-mediated allylation, propargylation, and benzylation of isatin-derived imines were undertaken for the synthesis of 3-substituted 3-aminooxindoles with ≈80% yield. Such alternative approach has efficiently avoided the use of catalysts, severe reaction conditions, multistep procedures, and reaction additives. For exploring and materializing the synthetic utility, different allyl, propargyl, and benzyl bromides were used for generalizing the synthetic route. The structure of the synthesized compounds was established and confirmed by 1H NMR, 13C NMR, FTIR, and mass spectroscopic techniques.

ChemInform Abstract: Zinc‐Mediated Allylation Followed by Lactonization of Dialkyl 2‐(3‐Oxo‐1,3‐diarylpropyl)malonates: Construction of δ‐Lactones with Multiple Stereocenters.

A variety of polysubstituted δ-lactones containing three or four stereocenters were prepared from various dialkyl 2-(3-oxo-1,3-diarylpropyl)malonates by a Barbier-type zinc-mediated allylation or cyclohexenylation of the keto group, followed by intramolecular lactonization/transesterification. The stereochemistry of the major isomers was confirmed by X-ray crystal structure analysis of representative compounds.

Zinc-Mediated Allylation and Benzylation of Phenylazocarboxylic Esters.

Allylation and benzylation of phenylazocarboxylic tert-butyl esters have been achieved under Barbier-type reaction conditions and in very short reactions times using the corresponding allyl and benzyl bromides or iodides in combination with zinc powder. Whereas all reactions occurred exclusively at the β-nitrogen atom of the azocarboxylic esters, the linkage of allyl units was shown to depend on the substitution pattern at the double bond of the allyl halide. The hydrazines obtained are useful precursors for indoles and indazoles.

Zinc-Mediated Allylation Followed by Lactonization of Dialkyl 2-(3-Oxo-1,3-diarylpropyl)malonates: Construction of δ-Lactones with Multiple Stereocenters

A variety of polysubstituted δ-lactones containing three or four stereocenters were prepared from various dialkyl 2-(3-oxo-1,3-diarylpropyl)malonates by a Barbier-type zinc-mediated allylation or cyclohexenylation of the keto group, followed by intramolecular lactonization/transesterification. The stereochemistry of the major isomers was confirmed by X-ray crystal structure analysis of representative compounds.

Zinc-mediated allylation of carbon dioxide—the LiOAc effect

A direct carboxylation reaction of allylic bromides mediated by zinc powder with 1 atm of CO2 provided by a balloon has been developed. The reaction occurred smoothly at room temperature in the presence of LiOAc with an excellent branched regioselectivity.

Zinc-Mediated Asymmetric Allylation of Chiral N-tert-Butanesulfinyl Aldimines with 3-Bromomethyl-5H-furan-2-one

The zinc-mediated asymmetric allylation of chiral N-tert-butanesulfinyl aldimines with 3-bromomethyl-5H-furan-2-one proceeded in good anti/syn selectivities, providing optically pure substituted alpha-methylene-gamma-butyrolactones bearing chiral amine wi

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.

Stereoselective total synthesis of cytotoxic sporiolide A

A simple and highly efficient stereoselective total synthesis of cytotoxic agent sporiolide A has been achieved starting from d-mannitol; the strategy of synthesis utilizes stereoselective zinc-mediated allylation, aldol coupling and ring-closing metathesis as key steps.

Stereoselective Total Synthesis of Cladospolide A

A simple and highly efficient stereoselective total synthesis of cladospolide A, a polyketide natural product, has been achieved. The synthesis involves stereoselective zinc-mediated allylation, pivotal aldol coupling, and ring-closing metathesis. The pivotal aldol coupling is used for the first time for macrolide construction and provides an effective alternative to Yamaguchi macrolactonization.

Zinc-Mediated Allylation and Alkylation of Aminals in the Presence of TMSCl and Diisopropylamine

An alkylation of aminals with organozinc reagents derived from allyl bromide, benzyl bromide, alpha-bromoacetate, and alpha-bromonitrile proceeded efficiently in the presence of TMSCl and diisopropylamine. This reaction system was applied to the synthesis of an antispasmodic: butaverine.

Zinc-mediated Allylation of Aryl 2-Propynyl Acetates: A Facile Synthesis of 1,5-Enynes

Abstract Aryl 2-propynyl acetates undergo smooth allylation with allylzinc bromide (generated in situ from allyl bromide and zinc metal) in THF at room temperature under mild conditions to furnish the corresponding 1,5-enynes in good to excellent yields and with high selectivity. Indium metal is also found to accomplish the nucleophilic substitution of aryl 2-propynylic acetates with allyl bromide.

Diastereoselective Allylation of Planar Chiral Substituted Ferrocenecarboxaldehyde: An Efficient Entry to Chiral Ferrocenyl Ligands.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Diastereoselective allylation of planar chiral substituted ferrocenecarboxaldehyde: an efficient entry to chiral ferrocenyl ligands

2,2′-Disubstituted ferrocenecarboxaldehydes are subjected to zinc-mediated allylation to form homoallylic ferrocenyl alcohols. The effects of ortho-substituted functional groups on facial selectivities of planar chiral aldehydes were studied and it was found that the corresponding homoallylic alcohols were obtained as single diastereomers in excellent yields.

The first total synthesis of ( S)-clavulazine from d-mannitol

The first total synthesis of the marine natural product, ( S)-clavulazine has been accomplished. d-Mannitol was used as a chiral starting material. Enantioselective zinc-mediated allylation, and ring-closing metathesis are the key steps in the synthesis. Subsequent condensation followed by dehydrogenation yielded the natural product, ( S)-clavulazine.

A Synthesis of Novel N‐Sulfonylated β‐Amino Acids.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

A synthesis of novel N-sulfonylated β-amino acids

Novel N-sulfonyl β-amino acids were efficiently prepared in a seven-step synthesis starting from Boc protected methanesulfonamide and terminal epoxides. A zinc-mediated allylation of cyclic N-sulfonyl imines readily derived from these building blocks served as a key operation of this sequence.

Indium- and zinc-mediated allylation of difluoroacetyltrialkylsilanes in aqueous media

Metal-mediated allylations of difluoroacetyltriakylsilanes with various allyl bromides in aqueous media form homoallylic alcohols exclusively. The common Brook rearrangement, carbon to oxygen-silyl migration, is totally suppressed with no detectable formation of silyl enol ether. Influence of solvents on reaction is studied. Reactivity differences between indium and zinc are also described.

New Organometallic Approach to Derivatives of α‐Substituted Statines from N,N‐Dibenzylaminoaldehydes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

New organometallic approach to derivatives of α-substituted statines from N, N-dibenzylaminoaldehydes

α-Substituted statines derivatives were synthesized via the zinc-mediated allylation of N, N-dibenzyl α-aminoaldehydes followed by ozonolysis of the intermediate homoallylic alcohols.