Morita Baylis Hillman Acetates Research Articles

Visible-Light-Promoted Iron(II)/Lewis Base Catalysis for the Alkylation of Morita-Baylis-Hillman Acetates Using Carboxylic Acids.

A novel photoinduced Fe(OTf)2/2,4,6-collidine-catalyzed alkylation of Morita-Baylis-Hillman (MBH) acetates using carboxylic acids in a regio- and stereoselective manner is reported. This method demonstrates a broad scope, encompassing various carboxylic acids and MBH acetates, including drugs and bioactive molecules, to synthesize densely functionalized cinnamates and acrylates. The reactions are performed in the green solvent dimethyl carbonate under oxidant-free conditions. Based on control experiments, a plausible mechanism involving an Fe(II)-Fe(III)-Fe(II) cycle is proposed.

Iodine‐Mediated One‐Pot Synthesis of 1,4,5‐Substituted Pyrazoles from MBH Acetates via Allyl Hydrazone Intermediate

AbstractHerein, we report the regioselective one‐pot synthesis of 1,4,5‐trisubstituted pyrazoles by reacting Morita‐Baylis‐Hillman (MBH) acetates derived from aryl aldehydes with alkyl or aryl hydrazines in the presence of iodine under aerobic conditions. The reaction proceeds through sequential SN2′ nucleophilic substitution of substituted hydrazine onto the MBH acetate, I2‐catalyzed oxidation of the allylic hydrazine to allylic hydrazone, heating‐induced intramolecular aza‐Michael reaction and cyclization, and oxidative aromatization. The key intermediate, thes‐transallyl hydrazones were isolated in good yields by performing the reactions at room temperature. However, the allyl hydrazones prepared from the MBH acetates of aliphatic aldehydes did not furnish the pyrazole owing to the absence of an activated methylene group in the substrate. The synthetic applications of the pyrazoles in Ugi reactions, decarboxylative halogenation, Pd‐catalyzed benzoylation of the N‐aryl ring, and metal‐free tetrazole synthesis has been demonstrated.

Vitamin B6-Based Biomimetic Asymmetric Catalysis

One of the fundamental goals of chemists is to develop highly efficient methods for producing optically active compounds, given their wide range of applications in chemistry, pharmaceutical industry, chemical biology, and material science. Biomimetic asymmetric catalysis, which imitates the structures and functions of enzymes, has emerged as an extremely attractive strategy for producing chiral compounds. This field has drawn tremendous research interest and has led to various protocols for constructing complex molecular scaffolds. The Vitamin B6 family, including pyridoxal, pyridoxamine, pyridoxine, and the corresponding phosphorylated derivatives, serves as the cofactors to catalyze more than 200 enzymatic functions, accounting for ∼4% of all enzyme activities. Although significant progress has been made in simulating the biological roles of vitamin B6 during the past several decades, its extraordinary catalytic power has not yet been successfully applied into asymmetric synthesis. In recent years, our group has been devoted to developing vitamin B6-based biomimetic asymmetric catalysis using chiral pyridoxals/pyridoxamines as catalysts. We are particularly interested in mimicking the processes of enzymatic transamination and biological aldol reaction of glycine, respectively, developing asymmetric biomimetic transamination and carbonyl catalysis enabled α-C-H transformation of primary amines. Using a chiral α,α-diarylprolinol-derived pyridoxal as the catalyst, we reported the first chiral pyridoxal catalyzed asymmetric transamination of α-keto acids in 2015. A significant breakthrough in biomimetic transamination was achieved by using an axially chiral biaryl pyridoxamine catalyst that bears a lateral amine side arm. The amine side arm acts as an intramolecular base, accelerating the transamination and proving highly effective for transamination of α-keto acids and α-keto amides. In addition, we discovered the catalytic power of chiral pyridoxals as carbonyl catalysts for asymmetric biomimetic Mannich/aldol reactions of glycinates. These chiral pyridoxals also enabled more α-C-H conversions of glycinates, such as asymmetric 1,4-addition toward α,β-unsaturated esters and asymmetric α-allylation with Morita-Baylis-Hillman acetates. Moreover, carbonyl catalysis can be further applied to highly challenging primary amines with inert α-C-H bonds, such as propargylamines and benzylamines, which represents a powerful strategy for direct asymmetric α-C-H functionalization of various primary amines without protection of the NH2 group. These biomimetic/bioinspired transformations provide efficient new protocols for the synthesis of chiral amines. Herein, we summarize our recent efforts on the development of the vitamin B6-based biomimetic asymmetric catalysis.

Synthesis and Elimination Pathways of 1-Methanesulfonyl-1,2-dihydroquinoline Sulfonamides

A series of new Morita-Baylis-Hillman acetates were prepared and reacted with methanesulfonamide (K2CO3, DMF, 23 °C) to produce tertiary dihydroquinoline sulfonamides in high yields. Subsequent efforts to eliminate the methylsulfonyl group from these derivatives (K2CO3, DMF, 90 °C) as a route to quinolines were met with mixed results. Although dihydroquinoline sulfonamides prepared from ethyl acrylate and acrylonitrile generally underwent elimination to give excellent yields of quinolines, those generated from 3-buten-2-one failed to undergo elimination and instead decomposed. The failure of these ketone substrates to aromatize presumably derives from the enolizable methyl ketone at C-3. Finally, the attempted aromatization of the acrylate-derived 6,7-difluoro-1,2-dihydroquinoline sulfonamide demonstrated that other interesting processes could occur in preference to the desired elimination.

Catalyst- and Additive-Free Electrochemical CO2 Fixation into Morita–Baylis–Hillman Acetates

AbstractThe electrochemical carboxylation of Morita–Baylis–Hillman (MBH) acetates with CO2 is presented. The process proceeds in the absence of transition-metal catalysts and relies on the cathodic reduction of MBH acetates to generate nucleophilic anions that are able to trap low-pressure CO2. Valuable succinate derivatives are obtained (20 examples) in high yields (up to 90%) and with excellent functional group tolerance. A remarkable substrate-controlled (electronic nature) regioselectivity of the transformation is documented along with a mechanistic rationale based on control experiments.

Recent advances in the synthetic applications of Morita-Baylis-Hillman and Rauhut-Currier adducts of nitroalkenes.

The Morita-Baylis-Hillman (MBH) and Rauhut-Currier (RC) adducts of nitroalkenes are important synthetic intermediates in organic synthesis. This review discusses the applications of different MBH and RC adducts of nitroalkenes such as MBH alcohols, acetates, bromides and hydrazinonitroalkenes as well as ketoalkylnitroalkenes in the synthesis of complex molecules including carbocycles and heterocycles. It also covers the mechanistic aspects, including the key intermediates and the reaction pathways. Early reports on MBH and RC reactions of nitroalkenes and applications of the products were covered in previous reviews. The present review covers the reports that appeared in the timeline of 2015-2023.

Synthesis of differentiated sulfur-containing polymers by regiodivergent polymerization of Morita–Baylis–Hillman acetates and thiols

Regiodivergent polymerization of Morita–Baylis–Hillman acetates and thiols afforded two differentiated sulfur-containing polymers, and the γ-polymers could be transformed into the corresponding α-polymers under radical conditions.

3+2]-Annulation of oxindolinyl-malononitriles with Morita–Baylis–Hillman acetates of nitroalkenes for the regio- and diastereoselective synthesis of spirocyclopentane-indolinones

3-Oxindolinyl-malononitrile participates as a 1,2-binucleophile in a highly regio- and stereoselective [3 + 2] annulation with 1,3-bielectrophilic nitroallylic acetates leading to spirocyclopentane-indolinones. The reaction takes place in the presence of DABCO in THF at room temperature and affords the multi-functional spirocyclic compounds possessing three chiral centers, including a spiro-chiral center in good to excellent yields and short reaction time. The key role of the malononitrile moiety in controlling the reactivity and selectivity has also been demonstrated. An SN2′-intramolecular Michael addition pathway is proposed for the [3 + 2] annulation based on DFT calculation results.

Synergistic photoredox and tertiary amine catalysis: generation of allylic sulfones from Morita–Baylis–Hillman acetates and sulfur dioxide

The first example of the synthesis of allylic sulfones through synergistic photoredox and tertiary amine catalysis, starting from MBH acetates, DABCO·(SO2)2 and 4-substituted Hantzsch esters or potassium alkyltrifluoroborates via a radical pathway, is reported.

Phosphinic Dehydrodipeptides: Diversification of the P1′ Residue with the Morita–Baylis–Hillman Acetates and Inhibition of Alanyl Aminopeptidases

Activated allyl acetates (the Morita–Baylis–Hillman acetates) were confirmed as convenient electrophilic precursors of the P1′ fragment of phosphinic dehydrodipeptides, and then, their selected saturated analogs were obtained in the subsequent reduction. This approach is particularly appropriate for structurally complex side chains and thus is an alternative to the addition of α-substituted acrylates with aminoalkylphosphinic acids. While phosphinic dehydrodipeptides were found to be good inhibitors of two mammalian alanyl metalloaminopeptidases, the saturated compounds showed higher activities than their structurally constrained counterparts. Docking calculations and molecular modeling showed that conformational freedom allowed for the favorable binding of distinct stereoisomers of phosphinates, while the presence of the double bond was more restrictive.

Synthetic Approaches to Nitro-Substituted Isoxazoles

Nitro-substituted isoxazoles are of utmost interest both as versatile intermediates for targeted organic synthesis and as perspective bioactive compounds for drug development. Nevertheless, the existing approaches to them usually lack generality and strongly depend on the position of the nitro group and on the presence of other substituents in the isoxazole ring. This review provides the first systematization of all available data concerning synthetic approaches to 3-, 4-, and 5-nitroisoxazoles. There are a number of preparative approaches to 4-nitroisoxazoles based on classical heterocyclization reactions of nitro-substituted compounds and the nitration of isoxazoles. 3-Nitro- and, especially, 5-nitroisoxazoles are much less readily available. A few methods affording 3-nitroisoxazoles have been reported, often employing the heterocyclization of unsaturated compounds by treatment with sodium nitrite. The sole general preparative method for 5-nitroisoxazoles, containing a variety of functional groups, employs the heterocyclization of electrophilic alkenes by treatment with tetranitromethane activated with triethylamine.1 Introduction2 Synthesis of 4-Nitroisoxazoles2.1 Nitration of Isoxazoles2.2 Condensations of α-Nitro Ketones or Their Oximes2.3 1,3-Dipolar Cycloaddition of Nitrile Oxides to Acetylenes and Their Synthetic Equivalents2.4 Heterocyclization of Acetylene Derivatives by Treatment with Sodium Nitrite2.5 Heterocyclization of Nitro Derivatives of 1,3-Diketones and Their Synthetic Equivalents2.6 Miscellaneous Methods3 Synthesis of 3-Nitroisoxazoles3.1 Heterocyclization of Acetylene Derivatives or 1,3-Dihalogenoalkenes by Treatment with Sodium Nitrite3.2 Heterocyclization of Morita–Baylis–Hillman Acetates by Treatment with Sodium Nitrite3.3 1,3-Dipolar Cycloadditions4 Synthesis of 5-Nitroisoxazoles4.1 1,3-Dipolar Cycloadditions4.2 Synthesis Using Polynitro Compounds5 Conclusion

Palladium‐Catalyzed Reaction of MBH Acetates and Terminal Alkynes: Cascade Synthesis of Phenanthridine and 6‐Arylethynylphenanthridine

We have described the palladium‐catalyzed regioselective cascade synthesis of phenanthridines and 6‐arylethynylphenanthridines in good to excellent yields from a reaction between Morita–Baylis–Hillman (MBH) acetates and terminal alkynes. These cascade reactions are temperature controlled and favor the formation of phenanthridines when conducted at 50 °C and of 6‐arylethynylphenanthridines when performed at 80 °C.

Amine‐Catalyzed Tandem Reactions of Morita–Baylis–Hillman Acetates with Isatins: Facile Synthesis of 3‐Hydroxyoxindoles

An amine‐catalyzed reaction between Morita–Baylis–Hillman (MBH) acetates and isatins to provide facile access to structurally interesting 3‐hydroxyoxindoles in moderate to good yields with diastereomeric ratios of 1:1 has been developed. A wide variety of isatin derivatives were tolerated under the conditions of this tandem reaction. Notably, the inert homoallylic methyl group of MBH acetate 1 was directly involved in the bond formation step, which was followed by a [4+2] annulation under mild conditions to lead to the desired products.

Development of Imidazole-Reactive Molecules Leading to a New Aggregation-Induced Emission Fluorophore Based on the Cinnamic Scaffold.

In order to obtain new fluorophores potentially useful in imidazole labeling and subsequent conjugation, a small series of Morita–Baylis–Hillman acetates (3a–c) was designed, synthesized, and reacted with imidazole. The optical properties of the corresponding imidazole derivatives 4a–c were analyzed both in solution and in the solid state. Although the solutions display a very weak emission, the powders show a blue emission, particularly enhanced in the case of compound 4c possessing two methoxy groups in the cinnamic scaffold. The photophysical study confirmed the hypothesis that the molecular rigidity of the solid state enhances the emission properties of these compounds by triggering the restriction of intramolecular motions, paving the way for their applications in fluorogenic labeling.

Stereoselectivity-Tailored, Metal-Free Hydrolytic Dynamic Kinetic Resolution of Morita–Baylis–Hillman Acetates Using an Engineered Lipase–Organic Base Cocatalyst

Metal-free enantiocomplementary hydrolytic dynamic kinetic resolution of Morita–Baylis–Hillman (MBH) acetates was developed using triethylamine (TEA) as a racemization catalyst and wild-type or engineered lipase B from Candida antarctica (CALB) as stereoselectivity-determining catalyst, leading to chiral MBH alcohols with tailor-made R or S configurations on an optional basis. In the TEA-WT CALB catalysis system, WT CALB displays excellent S enantioselectivity for a series of MBH acetates tested (up to 96% ee and 98% conversion). Reversal of enantioselectivity in favor of (R)-MBH alcohols (95% ee; 95% conversion) was achieved by generating a focused site-specific mutagenesis library composed of less than 20 variants. Molecular modeling explains the origin of stereoselectivity.

ChemInform Abstract: Asymmetric Synthesis of Pyrano[2,3‐c]pyrazoles via a Cascade Reaction Between Morita—Baylis—Hillman Acetates of Nitroalkenes and Pyrazolones.

AbstractOptimized conditions A) allow the preparation of the pharmaceutically important scaffold with excellent enantio‐ and diastereoselectivity.

Cascade SN2′–SNAr, Elimination, and 1,5‐Hydride Shift Reactions by Acetylacetone/Acetoacetic Esters: Synthesis of 9,10‐Dihydroacridines

A reaction involving the use of acetylacetone/methyl acetoacetate and Morita–Baylis–Hillman acetates for the efficient, one‐pot, metal‐free synthesis of 9,10‐dihydroacridines at room temperature was developed. The cascade of reactions involved sequential SN2′–SNAr reactions, elimination, and reduction through ketene generation and hydride transfer. Evidence for hydride shift via a ketene intermediate was also discussed.

ChemInform Abstract: Access to 4,6‐Diarylpicolinates via a Domino Reaction of Cyclic Sulfamidate Imines with Morita—Baylis—Hillman Acetates of Nitroolefins/Nitrodienes.

AbstractThe title process is advantageous with regards to operational simplicity, high yields and good functional group tolerance.

ChemInform Abstract: Synthesis of a Series of γ‐Keto Allyl Phosphonates.

AbstractCyclic Morita—Baylis—Hillman acetates are rapidly transformed into the corresponding γ‐keto allyl phosphonates by allylic nucleophilic substitution.

One‐Pot Synthesis of Nitronaphthalenes from Morita–Baylis–Hillman Acetates and Primary Nitroalkanes via Sequential SN2′‐Intramolecular Oxidative Nucleophilic Substitution of Hydrogen‐E2 Elimination

One‐Pot Synthesis of Nitronaphthalenes from Morita–Baylis–Hillman Acetates and Primary Nitroalkanes via Sequential S_N2′‐Intramolecular Oxidative Nucleophilic Substitution of Hydrogen‐E2 Elimination