Rhodium-catalyzed asymmetric coupling reaction of allylic ethers with arylboronic acids

An asymmetric allylic substitution of simple allylic ethers with arylboronic acids in the presence of a rhodium(I)/(R)-DTBM-SEGPHOS catalyst has been developed. The reactions proceeded smoothly at room temperature to give the corresponding branch products with excellent regioselectivities and good to excellent enantioselectivities.     

Regioselective cyclocondensation of ethyl 2-ethoxymethylidene-3-oxo-3-polyfluoroalkylpropionates with thiazolylhydrazines

Ethyl 2-ethoxymethylidene-3-oxo-3-polyfluoroalkylpropionates reacted in a regioselective fashion with thiazolylhydrazines to give the corresponding ethyl 1-thiazolyl-5-fluoroalkyl-1H-pyrazole-4-carboxylates. The product structure was determined on the basis of NMR and X-ray diffraction data.     

Regioselective reductive coupling of alkynes and aldehydes leading to allylic alcohols

Treatment of a mixture of a terminal alkyne and an aldehyde with CrCl(2) and a catalytic amount of NiCl(2) and triphenylphosphine in the presence of water in DMF at 25 degrees C gives a 1,2-disubstituted allylic alcohol regioselectively.     

Regioselective dehydroxytrifluoromethylthiolation of allylic and propargylic alcohols with AgSCF3

The reaction of easily available Morita–Baylis–Hillman (MBH) alcohols with AgSCF₃ in the presence of n-Bu₄NI and KI affords primary allylic SCF₃ products in high yields and excellent regioselectivities. This regioselective dehydroxytrifluoromethylthiolation protocol could also be extended to propargylic alcohols for the preparation of the primary propargylic SCF₃ products.     

Asymmetric allylic alkylation of acyclic allylic ethers with organolithium reagents

A highly efficient, regio- and enantioselective Cu(I) /phosphoramidite-catalyzed asymmetric allylic alkylation of allyl ethers with organolithium reagents is reported. The use of organolithium reagents is essential for this catalytic C?C bond formation due to their compatibility with different Lewis acids. The versatility of allylic ethers under the copper-catalyzed reaction conditions with organolithium reagents is demonstrated in the shortest synthesis of (S)-Arundic acid.     

Regioselective hydroformylation of allylic alcohols

A highly regioselective hydroformylation of allylic alcohols is reported toward the synthesis of β-hydroxy-acid and aldehyde products. The selectivity is achieved through the use of a ligand that reversibly binds to alcohols in situ, allowing for a directed hydroformylation to occur. The application to trisubstituted olefins was also demonstrated, which yields a single diastereomer product consistent with a stereospecific addition of CO and hydrogen.     

Nitriles in heterocyclic synthesis: Studies on ethyl 3-amino-4,4-dicyano-3-butenoate

New polyfunctionally substituted heterocyclic compounds were synthesized from ethyl 3-amino-4,4-dicyano-3-butenoate (1) as a starting material.     

Regioselective oxidative coupling reactions of 3-substituted thiophenes with arylboronic acids

Under optimized conditions, 3-substituted thiophenes (EWG = COOEt, PO(OEt)(2)) undergo a facile and regioselective oxidative coupling reaction at carbon atom C4. The reactions were performed with various aryl boronic acids as nucleophiles in the presence of silver oxide (2.0 equiv), cesium trifluoroacetate (tfa) (1.0 equiv), benzoquinone (BQ) (0.5 equiv), and catalytic amounts of Pd(tfa)(2) (10 mol %) employing trifluoroacetic acid (TFA) as the solvent.     

Regioselective synthesis of allylic sulfones by palladium-catalyzed denitro-sulfonylation of allylic nitro compounds

Allylic nitro compounds undergo denitro-sulfonylation catalyzed by Pd(PPh₃)₄ or Pd(PPh₃)₄ +NaNO₂ with PhSO₂Na·2H₂O to afford allylic sulfones regioselectively.     

Regioselective synthesis of trifluoromethyl group substituted allylic amines via palladium-catalyzed allylic amination

The palladium-catalyzed regioselective allylic amination of α-trifluoromethylated allyl acetate occurred using Pd(OAc)₂/DPPE and [Pd(π-allyl)(cod)]BF₄/DPPF. The selective formation of the γ-product was attained by Pd(OAc)₂/DPPE, while the α-product was obtained using [Pd(π-allyl)(cod)]BF₄/DPPF.     

Regioselective lithiation of aryl benzyl ethers

The lithiation of a series of aryl benzyl ethers containing -F and -OMe groups has been studied. It was found that the presence of one or two fluorine atoms in the meta position relative to the oxygen atom prevents the lithiation at the benzyl carbon atom. 3-(3′,5′-Dimethoxybenzyloxy)fluorobenzene was lithiated and next reacted with DMF to give 2-(3′,5′-dimethoxybenzyloxy)-6-fluorobenzaldehyde. A three-step procedure was applied to remove three hydrogen atoms from 1,3-difluoro-5-(3′,5′-dimethoxybenzyloxy)benzene and replace them with methyl groups by reactions of the lithiated compounds with MeI.     

Lewis acid-catalyzed nucleophilic substitutions of propargylic and allylic silyl ethers with enol silyl ethers

Nucleophilic reactions of various enol silyl ethers with carbocation species generated from propargyl silyl ethers by the action of a Lewis acid have been developed. The present method is highly useful for the introduction of allenic or enyne functionalities into the alpha-position of substituted ketones. [reaction--see text]     

Regioselective palladium-catalyzed formate reduction of N-heterocyclic allylic acetates

The regioselective palladium-catalyzed formate reduction of allylic acetates in five- to eight-membered heterocycles is reported. Reduction of allylic acetates under mild conditions using allylpalladium chloride dimer, phosphines, and formic acid/triethylamine in DMF gives the exo-cyclic olefins in good regioselectivities and high yields. Synthetic application in preparing N-tosyl-3-oxo-piperidine is also reported.     

Zirconium-mediated SN2' substitution of allylic ethers: regio- and stereospecific formation of protected allylic amines

A new zirconium-mediated, regio- and stereospecific SN2' substitution of allylic ethers with a nitrogen nucleophile has been developed. Cbz-protected amine products were isolated in high yield from reactions with a wide range of Z allylic ethers. A mechanism of the allylic substitution consistent with the results of the kinetics and kinetic isotope effect studies was proposed.     

Catalytic asymmetric synthesis of allylic aryl ethers

[reaction: see text] The reaction of trichloroacetimidate derivatives of (Z)-2-alken-1-ols with phenol nucleophiles in the presence of the palladium(II) catalyst [COP-OAc]2 provides 3-aryloxy-1-alkenes in high yields and high enantiomeric purity (typically 63-90% yield and 90-97% ee). The reaction is exemplified by 20 examples. The method employs 1 mol % of the commercially available catalysts (S)- or (R)-[COPOAc]2, produces the branched isomer with unprecedented regioselectivity, and is compatible with the presence of base-labile functionality in either reactant.     

Regioselective Synthesis of 3-[2-(Alkylsulfanyl)ethyl]pyrazoles by Reaction of Alkanethiols with 3-Alkenylpyrazoles

3-Alkenyl-5-chloropyrazoles reacted with alkanethiols on heating to 60°C to afford in good yields 3-[2-(alkylsulfanyl)ethyl]-5-chloropyrazoles as a result of anti-Markovnikov addition to the alkenyl group.     

Chain transfer and living functionalization of polymethacrylates by group transfer polymerization using ethyl 2-Phenyl-2-butenoate

A living functionalization method has been investigated for group transfer polymerization (GTP) of poly(alkyl methacrylates) using ethyl 2-phenyl-2-butenoate (EPB). The end-capping reactions of EPB to living trimethylsilyl ketene acetal-ended poly(methyl methacrylate) (PMMA) chain ends have been systematically studied and characterized by SEC, VPO, UV-visible spectrosocopy, ¹H and ¹³c NMR spectroscopy. The results of sequential monomer addition, varying stoichiometry and copolymerization indicate that EPB effects efficient chain end functionalization only at stoichiometric concentrations; chain transfer reactions (chain transfer constant = 0.4) occur with excess EPB and during copolymerization with MMA. Chain transfer reactions (chain transfer constant = 0.1) also occur when copolymerizing ethyl 2-methyl-2-butenoate with MMA.     

Asymmetric coupling of arylmagnesium bromides with allylic esters

Arylmagnesium bromides were allowed to react with 3-penten-2-yl (or 2-buten-1-yl) acetate (pivaloate, carbonate or methyl ether) in the presence of NiCl₂[(S, S)-Chiraphos] catalyst to afford (R)-4-aryl-2-pentene (or 3-aryl-1-butene) in high chemical and optical yields.