Indium-mediated alkynylation of Baylis-Hillman acetates: a novel route to 1,4-enynes

Baylis-Hillman acetates undergo smooth alkynylation with aryl-susbstituted iodoalkynes in the presence of indium metal in refluxing dichloromethane to furnish 1,4-enynes in high yields with (E)-stereoselectivity. In the absence of Lewis acid, the reaction follows both S_N2 and S_N2′ pathways affording 1:1 mixtures of 1,4-enynes. Upon addition of 10 mol % of InBr₃, the reaction proceeds preferably in the S_N2′ manner. In the case of adducts derived from acrylonitrile, the corresponding products are obtained in fairly good yields and with (Z)-stereoselectivity.     

A highly alpha-regioselective AgOTf-catalyzed nucleophilic substitution of the Baylis-Hillman acetates with indoles

An efficient method for highly alpha-regioselective nucleophilic substitution of the Baylis-Hillman acetates with indoles catalyzed by AgOTf in high yields (72-99%) has been developed. Reductive cyclization of the substitution products furnished the azepinoindole derivatives in good yields (up to 93%).     

Indium-mediated dehalogenation of haloheteroaromatics in water

It turned out that indium metal was applicable to the dehalogenation of aromatic halides in water. This method is facile and safe compared with the conventional methods such as Pd-C, Raney Ni, or halogen-metal exchange.     

Montmorillonite clay catalyzed alkylation of pyrroles and indoles with cyclic hemi-acetals

Cyclic hemiacetals such as 2-deoxy-d-ribose and 2-deoxy-d-glucose react smoothly with pyrroles and indoles on the surface of montmorillonite KSF clay under extremely mild reaction conditions to afford optically active di-pyrrolyl and bis-indolyl alkanols in good yields with high selectivity.     

Zinc mediated propenylation of Baylis-Hillman acetates

Allyl bromide efficiently reacts with Baylis-Hillman acetates in the presence of zinc and copper iodide resulting in substituted 1,5-dienes.     

Novel synthesis of indolylquinoline derivatives via the C-alkylation of Baylis-Hillman adducts

A new and simple method for the C-alkylation of indoles by various Baylis-Hillman adducts and the one-pot reductive cyclization of C-alkylated indole derivatives generated from 2-nitro-Baylis-Hillman adduct to form indolylquinoline derivatives is described.     

Fast diastereoselective Baylis-Hillman reaction by nitroalkenes: synthesis of di- and triene derivatives

The Baylis-Hillman reaction is performed using nitroalkenes as activated alkenes, ethyl-2-bromomethylacrylate as electrophilic acceptor and DBU as catalyst base. Nitro dienes are obtained in good yields and very short reaction times. Moreover, starting from appropriate nitroalkenes it is possible to realize one pot the synthesis of trienic systems.     

Platinum-catalyzed allylation of aminonaphthalenes with allylic acetates in water

The activation of C-O bonds in allylic acetates in water as a suspension medium has been accelerated by carrying out the reactions in the presence of platinum complexes associated with ligands. The platinum-catalyzed allylation of aminonaphthalenes using allylic acetates gave the corresponding N-allylic aminonaphthalenes in good yields.     

Reaction of indium ate complexes with allylic compounds. Controlling SN2/SN2′ selectivity by solvents

Vinyl and methylindium ate complexes (indates) were prepared and both the tendency of immigration and regioselectivity toward cinnamyl bromide were investigated. The vinyl group was more preferably transferred than the Me group, giving a regioisomeric mixture of S_N2 and S_N2′ products. The ratio of S_N2/S_N2′ selectivity can be controlled by solvents; in the presence of polar solvents, such as N-butylpyrrolidone (NBP) and THF, the S_N2′ product was mainly obtained, whereas the S_N2 product was selectively prepared in solutions containing hexane. The vinylindium compound, generated by the reaction of allylic-type diindium reagents with imine, was also converted to the corresponding vinyl indate, which was allowed to react with allyl chloride to give a three-component coupling product.     

First example of the Mislow-Braverman-Evans rearrangement retaining the sulfur atom on the original carbon

Treatment of 1-chloro-2-methylalkenyl p-tolyl sulfoxides with N-lithio 2-piperidone in THF at room temperature resulted in the formation of 1-chloro-2-(hydroxymethyl)alkenyl p-tolyl sulfides in good yields. This reaction is the first example of the Mislow-Braverman-Evans rearrangement retaining the sulfur atom on the original carbon.     

A tandem Finkelstein-rearrangement-elimination reaction: a straightforward synthetic route to allyl esters

Allyl esters can be obtained by a Finkelstein-rearrangement-elimination reaction of 2-chloro-1-(chloromethyl)ethyl esters induced by NaI. Sodium iodide can be used below equivalence using a reductive agent as sodium thiosulfate. High yields are obtained with most of the diverse esters studied. The method described avoids the use of allyl alcohol as a reagent. 2-Chloro-1-(chloromethyl)ethyl esters are prepared from glycerol, the main by-product of biodiesel industry. The effectiveness of iodine as reagent to hydrolyze allyl esters is also confirmed.     

First example of FeCl3-catalyzed alkylation of indoles with pinenes

Indoles undergo smooth alkylation with α- and β-pinenes in the presence of 20 mol % of anhydrous FeCl₃ under mild reaction conditions to produce a wide range of the corresponding 3-alkylated indoles in excellent yields with high trans-selectivity. This is the first example of alkylation of indoles with mono-terpenes.     

Synthesis of 4-arylidenecyclohexane-1,3-diones from the Baylis-Hillman acetates

Synthesis of 4-arylidenecyclohexane-1,3-dione derivatives was carried out from the Baylis-Hillman acetates. The potential utility of the prepared compounds for the synthesis of cyclohexanedione oxime ether herbicides was examined.     

Direct palladium-catalyzed allylic alkylations of alcohols with enamines: Synthesis of homoallyl ketones

An efficient, direct nucleophilic allylic substitution of α-, β- and γ-substituted alcohols with enamines, using the Pd(OAc)_2/PPh₃ catalyst system and ZnBr₂ as a promoter in CH₂Cl₂ at reflux, is reported. The reaction course was dependent on the steric hindrance at the α- or γ-positions with respect to the functionalized α-carbon, selectively affording in moderate to good yields, α- or γ-homoallyl ketones, the so-called “linear” and “branched” products, respectively.     

Ruthenium-catalyzed linear selective allylic aminations of monosubstituted allyl acetates

The ruthenium-catalyzed highly linear selective allylic amination of monosubstituted allylic acetates with secondary amines was developed. The regioselectivity was controlled by the Ru₃(CO)₁₂/2-DPPBA catalyst, and a linear-type aminated product was obtained as a single regioisomer.     

Arylations of allylic acetates with triarylbismuths as atom-efficient multi-coupling reagents under palladium catalysis

Arylation of allylic acetates employing triarylbismuths as multi-coupling reagents under palladium-catalyzed conditions was reported. Triarylbismuths as nucleophilic coupling partners were used in sub-stoichiometric amounts with respect to allylic acetates and thus served as atom-efficient multi-coupling reagents. A variety of allylic acetates were cross-coupled with triarylbismuths to furnish the corresponding functionalized 1,3-disubstituted propenes in good to excellent yields in short reaction times. The reported palladium protocol also yielded chemo-selective allylic arylations in high yields.     

First example of molecular iodine-catalyzed allylation and alkynylation of cyclic allylic acetates

Cyclic allylic acetates undergo smooth allylation and alkynylation with allyltrimethylsilane and alkynyl silanes in the presence of molecular iodine under mild conditions to afford the corresponding allylated and alkynylated cyclohexene derivatives in good yields with high selectivity.