Amination of the Baylis–Hillman Acetates in Ethanol

Baylis–Hillman acetates in EtOH were substituted by various nitrogen nucleophiles to give the corresponding trisubstituted alkenes in high yields.     

Accelerated Amination of Baylis–Hillman Acetates Under Ultrasound Irradiation

The amination of the Baylis–Hillman acetates with primary amines can be dramatically promoted with improved yields and shortened reaction time under ultrasound irradiation. The selected aromatic, heteroaromatic, and aliphatic amines were investigated as the effective candidates for the sonochemical transformation.     

Sm/HOAc/EtOH System–Mediated Reduction of Baylis–Hillman Acetates

Selective formation of (2E)‐2‐methylalk‐2‐enoates or 2‐methyl alkanoates could be achieved in moderate to good yields under mild conditions via Sm/HOAc/EtOH system–mediated reduction of Baylis–Hillman acetates depending on the amount of samarium consumed in the reactions.     

Morita–Baylis–Hillman reactions of isatins with allenoates

4-(N,N-dimethylamino)pyridine (DMAP) was found to be a fairly efficient catalyst for the Morita–Baylis–Hillman reactions of isatins with α-substituted allenoates to give the corresponding products in good to high yields with moderate diastereoselectivities under mild conditions.     

Efficient Synthesis of a New Type of Baylis–Hillman Adducts and Their Stereoselective Bromination

A new type of Baylis–Hillman adducts derived from chlorovinyl aldehydes were prepared via Vilsmeier reaction of ketones with a bis(trichloromethyl) carbonate (BTC)/DMF system to construct chlorovinyl aldehydes, followed by sonochemical Baylis–Hillman reaction under solvent-free conditions. The stereoselective bromination of these new compounds with a Br₂-Ph₃P system has been achieved efficiently with good to excellent yields under mild conditions.     

l-proline and l-histidine co-catalyzed Baylis–Hillman reaction

Baylis–Hillman reaction between an aldehyde and an activated alkene, such as alkyl vinyl ketones, acrylates, acrylonitrile, and vinylsulfones, giving the β-hydroxy-α-methylene carbonyl compounds, is a versatile and atom-economical carbon–carbon bond-forming reaction. This reaction usually is catalyzed by strong Lewis bases such as tertiary amines and suffers from slow reaction rate. In this paper the Baylis–Hillman reaction between arylaldehydes and methyl vinyl ketone was successfully realized by a catalytic amount of l-proline and l-histidine system to give the corresponding normal Baylis–Hillman adducts in moderate to high yields for the first time. The effects of solvent and reagent electro property on the yields of this reaction were also investigated. Proline and histidine are naturally widely present amino acids in food system; furthermore, aldehydes and activated alkenes can also be easily produced in food processing, so proline and histidine co-catalyzed Baylis–Hillman reaction may find application in explaining some phenomena in food processing.     

Simple and Advantageneous Stereoselective Synthesis of (Z)-Allyl Phosphonates Starting from Baylis–Hillman Adducts

Baylis–Hillman adducts 3-hydroxyl-2-methylene alkanoates have been converted in one pot into the corresponding (Z)-allyl phosphonates by treatment with FeCl₃ and trialkyl phosphites in toluene under reflux. The products are formed in excellent yields (88–98%) within 1–1.5 h. The process is highly convenient and efficient, cost-effective, and remarkably stereoselective.     

Stereoselective Michael Addition and Michael-aldol Tandem Reaction of Diorganyl Diselenides or Disulfides with Conjugated Alkynones Mediated by Samarium Diiodide

Stereoselective Michael addition and Michael-aldol tandem reaction of diorganyl diselenides and disulfides with conjugated alkynones mediated by samarium diiodide were studied. The reaction temperature was critical for the stereoselectivity, β-Organylselenoalkenones or β-organylthioalkenones and γ-organylselenoallylic alcohols or γ-organylthioallylic alcohols were prepared in good yields.     

Lipase-catalyzed kinetic resolution of Baylis–Hillman products

Lipase-catalyzed kinetic resolution of the various Baylis–Hillman products, α-methylene-β-hydroxy compounds, were examined. When lipase PS was used as a biocatalyst in acetonitrile, transesterification of racemic ethyl 3-hydroxy-2-methylenebutanoate or 3-hydroxy-2-methylenepentanoate proceeded in a practical enantiomeric excess. The resolution by hydrolysis of the acetate derivatives was also tried. In contrast, in case of racemic ethyl 3-acetoxy-2-methylenepentanoate, under the conditions using lipase AK, the E value of the resolution was >321.     

Diastereoselective peroxidation of derivatives of Baylis–Hillman adducts

Cyclic derivatives of Baylis–Hillman adducts were synthesized. Cobalt-catalyzed peroxidation of these cyclic lactones afforded silyl peroxides in diastereomeric ratios ranging from 91:9 to 97:3.     

Transition-metal-free nucleophilic allylic substitutions of Morita–Baylis–Hillman bromides with aliphatic and aromatic amines

A simple protocol for the preparation of functionalized allylic amines under mild, transition-metal-free conditions from the reaction of Morita–Baylis–Hillman (MBH) bromides with amines is described herein. The treatment of the MBH bromides with various amines in the presence of NaI and Et₃N in aqueous acetone solution and at room temperature affords the corresponding functionalized allyl amines in moderate to good yields (45–87%). The reaction is rapid and carried out at room temperature.     

Aza-Morita–Baylis–Hillman reaction with ion-supported Ph3P

Various N-tosyl arylimines reacted with methyl vinyl ketone and ethyl vinyl ketone in the presence of ion-supported Ph₃P A and B to give adducts, N-(2′-methylene-3′-oxo-1′-arylbutyl)-4-methylbenzenesulfonamides and N-(2′-methylene-3′-oxo-1′-arylpentyl)-4-methylbenzenesulfonamides, respectively, in good yields with high purity by simple diethyl ether extraction of the reaction mixture. Moreover, ion-supported Ph₃P A and B could be repeatedly used for the same reaction to provide the corresponding adducts while maintaining good yields with high purity.     

Asymmetric Morita–Baylis–Hillman reaction of chiral glyoxylates

The first Morita–Baylis–Hillman reaction of chiral glyoxylic acid derivatives, i.e. N-glyoxyloyl-(2R)-bornane-10,2-sultam and (−)-8-phenylmenthyl glyoxylate is described. The reaction with cyclic α,β-unsaturated ketones proceeded under the catalytic influence of dimethyl sulfide in the presence of titanium tetrachloride. The adducts were obtained with very high diastereoisomeric excess (over 95% d.e.) and typical yields of 78%. The absolute configuration of the newly created stereogenic center was established by X-ray crystallographic analysis.     

Transition metal-free direct nucleophilic α-substitution of Morita–Baylis–Hillman alcohols with amines and thiols

An efficient transition metal-free allylic nucleophilic α-substitution of Morita–Baylis–Hillman alcohols with both aliphatic and aromatic amines in refluxing toluene, using activated molecular sieves as additives, is described herein. The reaction proceeded with exclusive α-regioselectivity in moderate to excellent yields with the formation of water as the sole by-product. Under the same conditions, upon treatment of some thiols with the title substrates, allylic sulfides were obtained in excellent yields and high regioselectivity.     

Stereoselective synthesis of benzofulvenes via a palladium-catalyzed cyclization of 1,3-dienes derived from Morita–Baylis–Hillman adducts

A facile synthesis of benzofulvenes was carried out starting from the Morita–Baylis–Hillman adducts of 2-bromobenzaldehyde. The synthesis was carried out via the sequential bromination, Wittig reaction with aldehyde, and Pd-catalyzed intramolecular Mizoroki–Heck reaction. The stereochemistry of benzofulvenes was dependent on the reaction condition, especially on the kinds of base and reaction time, and the substituent of starting materials.     

Catalytic Effects in Baylis–Hillman Reactions of Chromone-3-carbaldehydes with Acrylonitrile and Methyl Acrylate

The effects of various catalysts, the solvent system, and the temperature on the efficiency and chemoselectivity of reactions of a series of chromone-3-carbaldehydes with acrylonitrile and methyl acrylate are discussed.     

Directed C−H Activation and Tandem Cross-Coupling Reactions Using Palladium Nanocatalysts with Controlled Oxidation

Controlled oxidation of palladium nanoparticles provided high-valent Pd^IV oxo-clusters which efficiently promote directed C−H halogenation reactions. In addition, palladium nanoparticles can undergo changes in oxidation states to provide both high-valent Pd^IV and low-valent Pd⁰ species within one system, and thus a tandem reaction of C−H halogenation and cross-coupling (C−N, C−C, and C−S bond formation) was successfully established.     

The coupling of potassium organotrifluoroborates with Baylis–Hillman derivatives via visible-light photoredox catalysis

Catalyzed by Ir[dF(CF₃)ppy]₂(dtbbpy)PF₆, the coupling of potassium organotrifluoroborates with Baylis–Hillman derivatives under visible light irradiation has been developed. Based on the mechanism of reductive quenching cycle, it provides an easy, mild, efficient method for the synthesis of a variety of α,β-unsaturated carboxylic esters derivatives in a broad scope of the substrates.     

Synthesis of functionalized and fused furans and pyrans from the Morita–Baylis–Hillman acetates of nitroalkenes

The Morita–Baylis–Hillman (MBH) acetates derived from nitroalkenes and ethyl glyoxylate have been transformed in one pot at room temperature to highly fused and functionalized furans and pyrans in good to excellent yield. The reaction involves a cascade Michael–oxa-Michael addition of β-dicarbonyl compounds to the MBH acetates in the presence of an amine base such as DABCO. An unusual switching of selectivity in the oxa-Michael addition from 5-exo-trig to 6-endo-trig was observed when the β-dicarbonyl compound was changed from acyclic or six-membered ring cyclic to five-membered ring cyclic system.