Efficient Baylis--Hillman reaction using stoichiometric base catalyst and an aqueous medium

Ionic Liquid-Immobilized Quinuclidine-Catalyzed Morita−Baylis−Hillman Reactions

[reaction: see text] The ionic liquid-bound quinuclidine catalyzed Baylis-Hillman reactions were investigated. The IL-supported catalyst showed equally good catalytic activity as compared with its nonimmobilized counterpart. The corresponding Baylis-Hillman adducts were obtained in moderate to high yields in all the cases tested. The IL-supported quinuclidine can be readily recovered and reused six times without significant loss of catalytic activity.

Remarkable rate acceleration of imidazole-promoted Baylis-Hillman reaction involving cyclic enones in basic water solution

The Baylis-Hillman reaction of cyclic enones was greatly accelerated in basic water solution with imidazoles as catalysts, which resulted in short reaction time, high yields, and expanding substrate scopes. Bicarbonate solution was shown to be the optimal reaction medium for the reaction in this study. The apparent "enhanced basicity" of imidazoles accounted for the rate increase in alkaline solution.

‘Double asymmetric induction’ as a novel tool for high stereocontrol in Baylis–Hillman reaction

The strategy of double asymmetric induction was utilized in Baylis-Hillman reaction for the first time by the coupling of chiral aldehydes with chiral acrylate (1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose-3-acrylate) to obtain corresponding adducts with high syn diastereoselectivities (de >90%) in moderate to good yields.

Synthetic Studies toward FR182877. Remarkable Solvent Effect in the Vinylogous Morita−Baylis−Hillman Cyclization

[reaction: see text]. The intramolecular vinylogous Morita-Baylis-Hillman reaction was explored to access the central cyclopentane ring of FR182877. The reaction manifold and product distribution is strikingly solvent and substrate dependent.

Dual nucleophilic catalysis with DABCO for the N-methylation of indoles

DABCO is an extremely active catalyst for the methylation of indoles in conjunction with dimethyl carbonate (DMC). This green chemistry is highly effective and produces N-methylindoles in nearly quantitative yields. The reaction sequence consists of competing alkylation and acylation pathways and involves 1,4-diazabicyclo[2.2.2]octane (DABCO) dually as a nucleophilic catalyst, ultimately resulting in a single product: the N-methylated indole.

First asymmetric synthesis of chiral beta-iodo Baylis-Hillman esters via tandem 1,4-conjugate addition/carbonyl coupling reactions

A new asymmetric approach to chiral beta-iodo Baylis-Hillman hydroxy esters was developed via a tandem asymmetric I-C/C-C formation reaction. The reaction was conveniently carried out by slow addition of diethylaluminum iodide into a mixture of aldehyde and alpha,beta-acetylenic menthyl ester in dichloromethane at -23 degrees C. Excellent geometric selectivity, promising diastereoselectivity and modest to high yields (up to 91%) were obtained.

A novel modified baylis-hillman reaction of propiolate

A new reaction of propiolates and aldehydes mediated by DABCO analogous to the Baylis-Hillman reaction is described. This reaction provided novel beta-functionalized Baylis-Hillman products and a new methodology for the generation of alkylidene carbene species.

Dramatic rate acceleration of the Baylis-Hillman reaction in homogeneous medium in the presence of water

[reaction: see text] In homogeneous H(2)O/solvent medium, the reaction rate of aromatic aldehydes and acrylonitrile or acrylate was greatly accelerated, which led to shorter reaction time, lower reaction temperature, and higher yield. In this reaction, Me(3)N, DMAP, DABCO, and urotropine were good catalysts. Except for low-carbon alcohols, tetrahydrofuran, 1,4-dioxane, and acetonitrile could be chosen as the solvent. Under this condition, the diastereoselective reaction of nitrobenzaldehyde and L-menthyl acrylate was realized with 88-99% de.

The Baylis-Hillman condensation of alpha,beta-conjugate cycloketones with aldehydes using diethylaluminum iodide alone as the promoter

The Baylis-Hillman condensation of three types of alpha,beta-conjugate cycloketones with aldehydes was successfully performed by using diethylaluminum iodide as the Lewis acid promoter alone without the direct use of a Lewis base. The reaction proceeded to completion at 0 degree C in CH2Cl2 within 24 h to give modest to good yields (53-72%).

TiCl4-Promoted Baylis−Hillman Reactions of Substituted 5-Isoxazolecarboxaldehydes with Cycloalkenones1

The Baylis-Hillman (BH) reaction of substituted 5-isoxazolecarboxaldehydes with cyclohexenone in the presence of TiCl(4) invariably lead to the formation of hemiacetals beside the BH adducts. A similar reaction in the presence of DABCO, DBU, or 3-HQN yielded minor quantities of phenols in addition to the usual BH adducts. Similar to 5-isoxazolecarboxaldehydes, the TiCl(4)-mediated BH reaction of cyclohexenone with various benzaldehydes also furnishes hemiacetals in considerable yields. The reaction mechanism involving the formation of alpha-chloromethyl enone as an intermediate has been proposed. The synthesis of hemiacetals 5 and 14 from compound 4 in the presence of cyclohexenone and cyclopentenone, respectively, under acidic conditions indicates that enolization and aromatization of the cyclohexene ring are the key steps in the reaction mechanism.

Lewis acid-promoted Baylis–Hillman-type reaction of α,β-unsaturated ethyl thioester with aldehydes without the use of a Lewis base

The Baylis-Hillman-type reaction of alpha,Beta-ethyl thioacrylate with aldehydes has been achieved using diethylaluminium iodide as the promoter without the direct use of any Lewis bases. The reaction provides an effective access to various alpha-methylene-Beta-hydroxy thioesters.