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Sequential one-pot 2-iodoxybenzoic acid (IBX) oxidation of Morita− Baylis−Hillman (MBH) adducts followed by catalyst-free indolizine conjugate addition was developed. The wide scopes of MBH adducts and indolizines were investigated, and densely functionalized adducts were obtained in yields of up to 94%. The conjugate addition step occurred in less than a minute at room temperature with total regioselectivity toward indolizine C3 carbon. Less nucleophilic C1 carbon was also alkylated when C3-substituted indolizines were employed as the substrate.

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.

The intramolecular CF•••HX (X = O or S) H-bond and J FH spin−spin coupling constants (SSCCs) in 2-fluorophenol and 2-fluorothiophenol were investigated experimentally by 1 H and 19 F NMR and theoretically in the framework of the natural bond orbital analysis. In contrast with recent findings from the literature, the results obtained in this work showed that an intramolecular H-bond is formed in the cis conformers and that it has an electrostatic origin. Such an intramolecular electrostatic H-bond is the interaction that rules the conformational preferences on these compounds. Moreover, the natural J-coupling analysis indicated that the J HF SSCC in 2-fluorophenol has its origin on LP(F)/σ OH steric interactions and should be labeled as 4TS J HF . On the other hand, the analogue SSCC for 2fluorothiophenol has its origin on the intramolecular H-bond LP(F) → σ SH * hyperconjugative interaction and should be described as a 1h J FH SSCC.

We describe that vinyl-oxadiazoles function as a new and efficient nucleophilic partner for the Morita−Baylis− Hillman (MBH) reaction. The reaction between 5-vinyl-3-aryl-1,2,4-oxadiazoles and aromatic and aliphatic aldehydes, catalyzed by DABCO in the absence of solvent, showed high efficiency to afford a new class of heterocyclic MBH adducts with potential biological activity on yields up to 99% and short reaction times. These synthetically attractive adducts bear a heterocyclic scaffold of large pharmaceutical and commercial interest associated with a plethora of biological effects and technological applications. We also demonstrate their synthetic usefulness by a photoinduced addition reaction to a polyfunctionalized amino alcohol.