Development of a Mild Procedure for the Addition of Bisulfite to Electrophilic Olefins

Vinylogous Nitro-Haloform Reaction Enables Aromatic Amination

The first example of an aromatic haloform reaction is reported, defining a conceptually new haloform-type approach to the metal-free functionalization of arenes. We demonstrated that heteroarenes bearing a vinylogous nitromethane system, via the stage of a trichloromethane derivative, could undergo aromatic amination to produce N-functionalized arenes in quantitative yields and without the need for transition-metal catalysis. The haloform-type amination was implemented in the development of effective orthogonal N-protection strategies, establishing a new promising N-protecting reagent.

Asymmetric Phase Transfer Catalysed Michael Addition of γ-Butenolide and N-Boc-Pyrrolidone to 4-Nitro-5-styrylisoxazoles

Herein we report the addition of acidic γ-butenolide and N-Boc-pyrrolidone to 4-nitro-5-styrylisoxazoles, a popular class of cinnamic ester synthetic equivalent. The reactions proceeded under the catalysis of Cinchona-based phase-transfer catalysts. Functionalised γ-butenolides were obtained in good isolated yields and moderate enantioselectivity (up to 74% ee).

Organocatalytic enantioselective synthesis of β-amino sulfonic acid derivatives

An unprecedented enantioselective conjugate addition reaction of sodium bisulfite to various nitrostyrenes occurred upon the influence of a bifunctional amino-thiourea organocatalyst; a strategy that opens a straightforward route to unprotected chiral taurine derivatives thanks to the reduction of the obtained β-nitroethanesulfonic acids into the corresponding amino derivatives.

First enantioselective synthesis of gingesulfonic acids and unequivocal determination of their absolute stereochemistry

Herein we report the first organocatalysed enantioselective synthesis of gingesulfonic acids and shogasulfonic acids via a mild and convenient aminothiourea-catalysed conjugate addition of bisulfite to the olefin moiety of α,β-unsaturated carbonyls-a technology previously reported by us. A series of optically active naturally occurring sulfonic acids are prepared in their natural and unnatural configurations, and their absolute configurations are unequivocally confirmed by single crystal X-ray diffractometry.

One-Pot Synthesis of 4-Carboalkoxy-Substituted Benzo[h]coumarins from α- and β-Naphthols and Their Excited-State Properties

One-pot synthesis has been developed for 4-carboethoxybenzo[h]coumarins starting from α-/β-naphthols. Accordingly, diverse 4-carboethoxybenzocoumarins can be synthesized in moderate-to-excellent (31-75%) isolated yields. The synthesis involves initial oxidation of naphthols to the intermediary 1,2-naphthoquinones with 2-iodoxybenzoic acid followed by a cascade of reactions, namely, Wittig olefination, Michael addition, β-elimination, and cyclization. Furthermore, we have comprehensively investigated the excited-state properties of differently substituted 4-carboalkoxybenzo[h]coumarins. It is shown that they exhibit low to high fluorescence quantum yields (1-36%) and excited-state lifetimes (ca. 1-7 ns) depending on the substitution pattern and solvent employed.

Ligand-controlled stereodivergent 1,3-dipolar cycloaddition of azomethine ylides with 3-methyl-4-nitro-5-styrylisoxazoles

An unprecedented Ag(i)-catalyzed ligand-controlled stereodivergent 1,3-dipolar cycloaddition of azomethine ylides with 3-methyl-4-nitro-5-styrylisoxazoles has been developed to afford heterocycles bearing both methylisoxazole and pyrrolidine moieties.

Organocatalytic one-pot 1,4-/1,6-/1,2-addition sequence for the stereocontrolled formation of six consecutive stereocenters

An unprecedented stereoselective organocatalytic one-pot 1,4-/1,6-/1,2-addition sequence between β-dicarbonyl compounds, β-nitroalkenes and 4-nitro-5-styrylisoxazoles sequentially catalyzed by low loading of a squaramide catalyst and an achiral base has been developed. The protocol opens an efficient entry to isoxazole bearing cyclohexanes with six consecutive stereogenic centers including one tetrasubstituted carbon in good yields and excellent diastereo- and enantioselectivities.

An improved procedure to prepare 3-methyl-4-nitroalkylenethylisoxazoles and their reaction under catalytic enantioselective Michael addition with nitromethane

A two-step preparation of 3-methyl-4-nitro-5-alkylethenyl isoxazoles is herein reported. These were reacted with nitromethane under phase-transfer catalysis to provide highly enantioenriched adducts (up to 93% ee).

One-pot synthesis of functionalized isoxazole–thiolane hybrids via Knoevenagel condensation and domino sulfa-1,6-Michael/intramolecular vinylogous Henry reactions

One-pot synthesis of isoxazole–thiolane hybrids are reported via the Knoevenagel condensation, domino sulfa-1,6-Michael/intramolecular vinylogous Henry reactions using piperidine (30 mol%) with >95% yields in 2–2.5 h overall reaction time.

The Role of Surface Active Agents in Sulfonation of Double Bonds

Sulfosuccinate esters are vastly used in different formulations as wetting agents and dispersants. Hemi-ester, diester, ethoxylated, and ethoxylated ester derivatives of maleic anhydride, maleic acid, and fumaric acid are converted to the saturated or corresponding sulfosuccinates by the reaction of the double bond with sodium bisulfite in basic media. The roles of anionic, cationic and non-ionic surfactants have been investigated. Appropriate surfactants have been applied in the absence of a peroxide initiator. The results obtained show increased reaction rates. Characterization of the products was performed by FTIR and 1H-NMR spectroscopy. Ethoxylated isooctyl maleate derivative was used as the starting material and the sulfonation agents used were sodium bisulfite and meta bisulfite.