Titanium(IV) chloride and quaternary ammonium salt promoted Baylis-Hillman reaction

The Baylis-Hillman Reactions of Aldehydes with Methyl Vinyl Ketone in the Presence of Imidazole, Binol and Silica Gel

In the Baylis–Hillman reaction of aldehydes with methyl vinyl ketone, we found that, in the presence of a stoichiometric amount of binol and silica gel (SiO2), a weak Lewis base such as imidazole can promote the reaction to give the normal Baylis–Hillman adduct under good yields under heterogeneous reaction conditions.

Manganese-catalyzed ring-opening chlorination of cyclobutanols: regiospecific synthesis of γ-chloroketones

An efficient, mild, and practical ring-opening chlorination of cyclobutanols is developed by means of manganese catalysis.

Insights into the Morita–Baylis–Hillman reaction of isomeric dibenzofuran carbaldehydes: a theoretical and mass spectral study

Systematic theoretical and mass spectral investigations on the faster Morita–Baylis–Hillman (MBH) reaction of dibenzofuran-4-carbaldehyde (2) compared to its isomer, dibenzofuran-2-carbaldehyde (1) are described.

Bifunctional Polymeric Organocatalysts and Their Application in the Cooperative Catalysis of Morita–Baylis–Hillman Reactions

A series of soluble, non-cross-linked polystyrene-supported triphenylphosphane and 4-dimethylaminopyridine reagents were prepared. Some of these polymeric reagents contained either alkyl alcohol or phenol groups on the polymer backbone. The use of these materials as organocatalysts in a range of Morita-Baylis-Hillman reactions indicated that hydroxyl groups could participate in the reactions and accelerate product formation. In the cases examined, phenol groups were more effective than alkyl alcohol groups for catalyzing the reactions. This article is one of the first reports of the synthesis and use of non-natural, bifunctional polymeric reagents for use in organic synthesis in which both functional groups can cooperatively participate in the catalysis of reactions.

Traditional Morita–Baylis–Hillman reaction of aldehydes with methyl vinyl ketone co-catalyzed by triphenylphosphine and nitrophenol

In the Morita-Baylis-Hillman reaction of aldehydes with methyl vinyl ketone (MVK), we found that in the presence of a catalytic amount of phenol, the Lewis base triphenylphosphine can effectively promote the reaction to give the corresponding normal Morita-Baylis-Hillman adducts in good yields. The mechanism has been investigated by 31P NMR spectroscopy. The solvent and substituent effects were also examined.

Catalytic, Asymmetric Aza-Baylis-Hillman Reaction ofN-Sulfonated Imines with Activated Olefins by Quinidine-Derived Chiral Amines

The chiral nitrogen Lewis base, tricyclic cinchona alkaloid derivative TQO, is an effective promoter in the catalytic, asymmetric aza-Baylis-Hillman reaction of N-sulfonated imines Ar-CH=NR' 1 (R' = Ts, Ms, Ns, SES) with various activated olefins such as methyl vinyl ketone (MVK), ethyl vinyl ketone (EVK), acrolein, methyl acrylate, phenyl acrylate, or alpha-naphthyl acrylate to give the corresponding adducts in moderate to good yields with good to high ee (up to 99 %) at -30 degrees C or 45 degrees C in various solvents, including DMF/MeCN (1:1, v/v). The first such reaction of 1 with the simplest Michael acceptor MVK and methyl acrylate has been achieved with excellent enantioselectivity. The adducts derived from MVK and EVK had the opposite absolute configuration to those from acrolein, methyl acrylate, phenyl acrylate, and alpha-naphthyl acrylate. A plausible mechanism has been proposed on the basis of previous reports and the authors' investigations. An effective bifunctional chiral nitrogen Lewis base-Brønsted acid system has been revealed in this type of aza-Baylis-Hillman reaction.

Efficient Baylis-Hillman reactions of cyclic enones in methanol as catalyzed by methoxide anion

The Baylis-Hillman reactions of cyclic enones with a variety of aldehydes were investigated. 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) was found to be a viable catalyst in promoting the reactions of sterically retarded substrates in methanol. The reactions showed clear solvent dependence and only occurred in hydroxylic solvents, especially in methanol. Further consideration on the steric character of DBU and its high basicity jointly with other experimental observations suggests that the methoxide anion should be the "true" Baylis-Hillman catalyst. This has been confirmed by the effectiveness of similar reactions directly employing methoxide as the catalyst. The reaction pathways of this type of catalysis are proposed to depend on the choice of substrates. Supporting experimental observations were demonstrated and discussed in relation to mechanistic considerations. This study also reveals that both DBU and sodium methoxide can be successfully applied as effective catalysts in methanol to promote the Baylis-Hillman reactions for a range of cyclic enones including cyclopent-2-enones, cyclohex-2-enones, gamma-pyrone, and 1-benzopyran-4(4H)-ones.

DABCO catalyzed addition of selenosulfonates to α,β-unsaturated ketones

In the presence of DABCO (30 mol%), the addition of various selenosulfonates to alpha,beta-unsaturated ketones proceeded smoothly to give the corresponding adducts in good yields under mild conditions.

Steric factors direct Baylis-Hillman and aldol reactions in titanium tetrachloride mediated coupling between alpha-keto esters and cyclohex-2-enone derivatives

The titanium tetrachloride mediated reaction of alpha-keto esters with 5,5-dimethylcyclohex-2-enone provides the corresponding Baylis-Hillman adducts exclusively whereas a similar reaction of alpha-keto esters with cyclohex-2-enone furnishes the corresponding aldol adducts (with high syn-diasteroeselectivity) as the major product (along with the Baylis-Hillman adducts as the minor product), thus clearly demonstrating the role of the steric factors in directing the reaction pathway.

An unexpected highly stereoselective double aza-Baylis-Hillman reaction of sulfonated imines with phenyl vinyl ketone

The aza-Baylis-Hillman reaction of N-sulfonated imine with phenyl vinyl ketone gave the double aza-Baylis-Hillman adduct in good yields with excellent stereoselectivities in the presence of Lewis base 1,4-diazabicyclo[2.2.2]octane.

A novel titanium tetrahalide-mediated carbon-carbon bond-forming reaction: regioselective synthesis of substituted (E,Z)-1,5-dihalo-1,4-dienes

Reactions of aldehydes with 2 equiv of alkyne in the presence of TiX(4) (X = Cl, Br) regioselectively generated 1,5-dihalo-1,4-dienes in moderate to good yields with high (E,Z)-stereoselectivity. [reaction: see text]

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.