IBX‐Mediated Dehydrogenation of Substituted β‐Oxonitriles

Abstract

A convenient method for the mild dehydrogenation of β‐oxonitriles is presented. When treated with o‐iodoxybenzoic acid (IBX), a range of these compounds were transformed into their unsaturated counterparts. Furthermore, we show that the products of the dehydrogenation can react in situ, undergoing rapid hetero‐Diels–Alder reactions with enol ethers to give multiply substituted dihydropyrans. We also describe the dehydrogenation of cyclic β‐oxonitriles, which leads to the formation of substituted phenols.

Advances in Synthetic Applications of Hypervalent Iodine Compounds

“…IBX 535 has been be used as reagent for the synthesis of heterocyclic products. − For example, the IBX-mediated synthesis of functionalized pyridines 568 from β-enamino esters 566 and allylic alcohols 567 has been reported by Pal and Iqbal (Scheme ). This new methodology can afford 2-substituted nicotinic acids, tetrasubstituted unsymmetrical pyridines, and precursors of azafluorenones …”

Access to β‐Ketonitriles through Nickel‐Catalyzed Carbonylative Coupling of α‐Bromonitriles with Alkylzinc Reagents

“…β‐Ketonitriles serve as useful reactive precursors in organic synthesis . Due to the relative position of the ketone and nitrile functionalities, this class of organic compounds has been exploited for the synthesis of numerous heterocycles, including isoxazoles, pyrazoles, pyrimidines, pyrans, and thiazolidines, representing important structural fragments of biologically active molecules. Furthermore, the enantioselective reduction of β‐ketonitriles yields β‐hydroxynitriles that are common intermediates for the preparation of various pharmaceuticals, for example, the antiparasitic agent, levamisole …”

“…[1] Due to the relative position of the ketonea nd nitrile functionalities, this class of organic compoundsh as been exploited for the synthesis of numerous heterocycles, including isoxazoles, [2] pyrazoles, [3] pyrimidines, [4,5] pyrans, [6] and thiazolidines, [7] representing important structuralf ragments of biologically active molecules. [1] Due to the relative position of the ketonea nd nitrile functionalities, this class of organic compoundsh as been exploited for the synthesis of numerous heterocycles, including isoxazoles, [2] pyrazoles, [3] pyrimidines, [4,5] pyrans, [6] and thiazolidines, [7] representing important structuralf ragments of biologically active molecules.…”

Transition‐Metal‐Catalyzed α,β‐Dehydrogenation of Carbonyl Compounds

“…IBX) as the oxidants to prepare the unsaturated aldehydes and ketones with dimethylsulfoxide as the solvent [10a,b] . Luo and some other groups also reported related works by using hypervalent iodine reagents as the oxidants [10c–t] . Besides, Chen group developed the iodine‐catalyzed α , β ‐dehydrogenation of ketones and aldehydes (I 2 /KI/DMSO system) [10u] .…”