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The formation of carbon-carbon sigma bonds by the organocatalyzed Morita-Baylis-Hillman (MBH) constitutes a sustainable way for the synthesis of valuable, highly functionalized molecules. Its large-scale implementation is however hampered both by its poor performance with substrates such as α,β-unsaturated ketones and by the reduction of the nucleophilicity of the catalyst when using water as solvent. Recent work from our laboratories has shown that a bicyclic imidazolyl alcohol (BIA), overcomes these limitations and is a much more efficient catalyst than imidazole for the aqueous MBH reactions of cyclic enones. The role of the hydroxyl group in the former catalyst is not easy to understand, however, since these reactions take place in water solution. We have studied the mechanism of the aqueous Morita-Baylis-Hillman (MBH) reaction between 2-cyclohexenone and isatin, catalyzed either by imidazole or by the BIA catalyst, using a combined experimental and computational approach. The data allowed us to propose mechanistic free-energy profiles for the two catalysts. An intramolecular proton transfer step, facilitated by the hydroxyl group of the catalyst even if the reaction takes place in water, accounts for the higher catalytic efficiency of BIA in comparison to imidazole, which requires assistance by an external base (either hydroxide ion or another imidazole molecule) for this catalytic step. The computed activation energies are in good agreement with the experimentally observed trends in reaction rates. The crucial role of the BIA hydroxyl has been confirmed by NMR study of the reaction kinetics, and in situ ESI-MS/MS monitoring experiments have detected and characterized all the relevant reaction intermediates, validating the computational model. To the best of our knowledge, this is the first study that provides clear evidence for the intramolecular participation of a bifunctional catalyst in the proton transfer step of a MBH reaction. The fact that the introduction of a suitable functional group favors the intramolecular proton transfer over solvent-mediated pathways, just in the spirit of enzymatic catalysis, provides a basis for the rational design of future efficient catalysts for aqueous reactions.

A series of phthalic anhydrides underwent a 1,3-dipolar cycloaddition reaction with N-benzylazomethine ylide to produce unstable spiro(isobenzofuran-1,5′-oxazolidin)-3-ones, which underwent a subsequent reductive ring-opening reaction to afford 1(3H)-isobenzofuranones.

Since its discovery in the late 1960s, the Morita–Baylis–Hillman (MBH) reaction has remained a powerful carbon–carbon σ-bond-forming transformation, producing small polyfunctionalized molecules. While commonly catalyzed by Lewis basic organic molecules such as tertiary amines and phosphines, several advances in functional catalysts and reaction conditions have been made in order to improve the reaction rate, substrate scope, and enantioselectivity. The goal of this Review is to give an updated summary of the main improvements made in catalytic systems for the MBH reaction over the past decade until nowadays. We hope this account will instigate further investigations in order to circumvent the remaining challenges of this fascinating transformation.

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The Morita-Baylis-Hillman (MBH) reaction has been stablished as an important CÀ C bond-forming transformation between carbonyl-containing compounds and activated olefins. However, the slow reaction rate usually observed with electron-rich electrophilic partners hinders a more widespread use of this reaction. In order to overcome this drawback, the effects of several Brønsted acids on the rate of DABCO-catalyzed MBH reactions were evaluated. The protocol is operationally simple, involving neat and open-flask conditions, and is compatible with a wide range of reagents. We suggest a general acid catalysis mechanism to be responsible for the rate increase. The synthetic versatility of the MBH adducts is exemplified with a two-steps diastereoselective synthesis of the natural product (�)-sitophilure. We hope this acid-mediated protocol to have potential use as a general methodology for the MBH reaction.

We reported herein an N‐heterocyclic carbene (NHC)‐mediated intermolecular Stetter reaction between oxidized Morita‐Baylis‐Hillman (MBH) adducts and a variety of aldehydes. This protocol allows the synthesis of highly functionalized 1,4‐dicarbonyl compounds. The reaction is an alternative approach to these compounds using commercially available starting materials. This metal‐free process exhibits a wide substrate scope, excellent atom economy, compatibility with functionalized substrates and mild reaction conditions. The 1,4‐dicarbonyl compounds were prepared in two steps via MBH reactions with overall yields up to 99 %. This protocol is easily scalable. The synthetic usefulness of this method was demonstrated in a high yield synthesis of a tri‐substituted pyrrole used as an advanced intermediate in the total synthesis of kinase inhibitors as well as in the synthesis of another heterocycles.