Nitrostyrene-Derived MBH Adducts as Electrophiles, Bis-Electrophiles and Ambiphiles: Diversified Reactivity at α, β,...

The Morita-Baylis-Hillman (MBH) reaction is one of the most powerful and versatile organocatalytic transformations for constructing carbon-carbon, carbon-nitrogen, and carbon- sulphur bonds. Owing to its high atom economy and operational simplicity, the MBH reaction has found widespread applications in the synthesis of heterocyclic frameworks, biologically active molecules, and key intermediates for pharmaceuticals and functional materials. Among various MBH substrates, nitroallylic MBH adducts derived from β-nitrostyrene have gained significant attention due to their unique electronic properties and multifaceted reactivity. The presence of a strong electron-withdrawing nitro group in conjunction with an allylic alcohol moiety renders these adducts highly reactive and tunable intermediates. This review comprehensively summarizes recent advances in the diversified functionalization of nitroallylic MBH acetates, with a particular emphasis on their application in the construction of structurally diverse heterocyclic compounds. A wide range of heterocycles, including furan derivatives, naphthopyrans, pyrazoles, imidazoles, imidazo[ 1,2-a]pyridines, pyrroles, benzimidazothiazines, benzimidazothiazoles, dihydroazopyrimidines, indolizines, 6-(2-hydroxyaryl)picolinates, meta-terphenyls, 4,6-diarylpicolinates, 2-aryl terephthalates, diazepinones, benzo[b][1,6]naphtho[2,3-d]oxazocin-2-ones, and tetrahydrospiropyrans are discussed in detail. β-Nitrostyrene, readily prepared via a simple nitro-aldol reaction, serves as an ideal activated olefin for MBH reactions with various electrophiles. This review highlights the reactions of β-nitrostyrene with aldehydes and ethyl glyoxalate to afford the corresponding MBH adducts. In comparison, reactions with prochiral electrophiles such as formaldehyde generate primary MBH alcohols; reactions with ethyl glyoxalate yield secondary MBH alcohols. The synthetic utility of these MBH alcohols as 1,4-ambiphiles is critically examined. Furthermore, transformations at the chiral center, including conversion to acetate (-OAc) and arylamino (-NH- Ar) functionalities, are elaborated. Collectively, the diverse reactivity of β-nitrostyrene-derived MBH adducts as electrophiles, bis-electrophiles, and ambiphiles is systematically covered, highlighting their strategic importance in modern synthetic organic chemistry. This review is expected to inspire the development of new and efficient synthetic protocols exploiting this emerging and versatile class of MBH adducts.