Asymmetric Catalytic Approaches Employing α,β‐Unsaturated Imines

Abstract

Nitrogen-containing heterocyclic compounds have consistently been a noticeable center of attention due to their significant utilization in the domain of synthetic organic chemistry, agrochemicals, and pharmaceuticals. α,β-Unsaturated imines or conjugated imines provide a lot of significant cyclic as well as acyclic products through reacting with a versatile family of compounds. This review summarizes the recent advances in enantioselective reactions of α,β-unsaturated imines by using synthetic methodologies for synthesizing various nitrogencontaining heterocycles that contain four to six-membered rings. The synthesis of rarely found seven-, eight-and ninemembered nitrogen-containing heterocycles have also been reported.

Green and Efficient Chemo-selective Synthesis of Chalcone Imines (α,β-Unsaturated imine) using Baker’s Yeast

“…Such imines or conjugated imines provide a lot of significant cyclic as well as acyclic products through diverse reactivity with a versatile family of compounds [14,15]. The literature revealed that α,β-unsaturated imines can be prepared the following reactions by (i) heat elimination of imino-alcohol skeleton; (ii) allyl cation-mediated Schmidt between azides and alcohols; (iii) aza-Wittig reaction of αketophosphonates and trimethyl phosphazenes and (iv) dehydrogenative coupling between primary allylic alcohol and a primary amine [16]. Recently, Sc(OTf)3-catalyzed annulations reactions of vinyl diazoacetates with in situ formation of indole-derived, α,β-unsaturated imines for the preparation of cyclopenta[b]indoles has been reported [17].…”

Diastereo- and Enantioselective Synthesis of Eight-Membered N-Heterocycles from Benzofuran-Derived Azadienes and Ynones

“…The benzofuran-derived azadienes have long been regarded as competent four-atom synthons for constructing N-heterocycle scaffolds via catalytic asymmetric [4+n] cyclizations . In this context, a sequential enantioselective α-conjugate addition/cyclization of ynones bearing acidic α-H and benzofuran-derived azadienes, promoted by chiral bifunctional squaramide and DBU catalysis (Scheme b), was envisioned to provide chiral eight-membered N-heterocycles even though it may be challenging to control the chemo- and regioselectivity as the undesired [4 + 2] competing pathway initiated by β-cyclization .…”

Palladium-catalyzed asymmetric [4 + 3] cycloaddition of acyclic α,β-unsaturated imines with trimethylenemethane donors: access to chiral non-fused azepines

“…Acyclic α,β-unsaturated imines, which served as an efficient source of four-atom synthons for the construction of nitrogen heterocyclic compounds, have received much attention. 16 Over the past decade, the asymmetric [4 + 1] and [4 + 2] cycloaddition reactions involving acyclic α,β-unsaturated imines have been extensively studied to access structurally diverse five- and six-membered nitrogen-containing heterocycles. 17,18 Recently, these imines have also been utilized in the catalytic [4 + 4] 19 and [4 + 5] 20 cycloaddition reactions.…”