Exploring Morita-Baylis-Hillman reactions of p-quinols

The Morita-Baylis-Hillman reaction of p-methylquinols with activated aromatic aldehydes has been studied. Depending on the reaction conditions (solvent and additives), three different products were formed. A mono or double Morita-Baylis-Hillman adduct and a fused 1,3-dioxolane could be obtained in good chemical yields. The use of non-nucleophilic bases to promote the reaction suggested an autocatalytic mechanism.

Enantioselective, organocatalytic Morita-Baylis-Hillman and Aza-Morita-Baylis-Hillman reactions: stereochemical issues

Conscious of the importance that stereochemical issues may have on the design of efficient organocatalyts for both Morita-Baylis-Hillman and aza-Morita-Baylis-Hillman reaction we have analyzed them in this minireview. The so-called standard reactions involve "naked" enolates which therefore should lead to the syn adducts as the major products, irrespective of the E, Z stereochemistry of the enolate. Accordingly, provided the second step is rate determining step, the design of successful bifunctional or polyfunctional catalysts has to consider the geometrical requirements imposed by the transition structures of the second step of these reactions. On the other hand, MBH and aza-MBH reactions co-catalyzed by (S)-proline and a secondary or tertiary amine (co-catalyst) involve the aldol-type condensation of either a 3-amino-substituted enamine, dienamine, or both, depending on the cases. A Zimmerman-Traxler mechanism defines the stereochemical issues regarding these co-catalyzed condensations which parallel those of the well established (S)-proline catalyzed aldol-like reactions.