IBX-Mediated Organic Transformations in Heterocyclic Chemistry-A Decade Update

Abstract

O-Iodoxybenzoic acid (IBX) is a very mild and efficient hypervalent iodine synthetic reagent useful to carry out several selective oxidations. The present review highlights research reports on IBX-assisted transformations in heterocyclic derivatives, particularly from 2010 onward.

Total synthesis of Oboflavanone B

“…Since the hydroxyl groups have to be protected at the beginning, stable hydroxyl protecting groups (TBS) play vital roles because they will hardly be destroyed in the case of long reaction time and severe reaction conditions. The coupling reaction of fragment 4 and fragment 5 utilize heck reaction which showed a high yield according to the previous work (see Figure 9) [12]. Besides, in the process of the ring formation, another hydroxyl protecting group (Fmoc) is stable enough to undergo the strong acidic environment.…”

“…Then, available reagent 13 is supposed to react with the aldehyde group of the compound 12 under the existence of magnesium catalyst, which can combine with 13 to generate Grignard reagent (see Figure 10). Although there is no similar history reaction found in this structure, the reaction is supposed to be feasible, because the reactivity of aldehyde is far greater than that of ester group and carbonyl group on the molecule (12). Simply put, the Grignard reagent will possibly addition to the aldehyde first, so it requires us to control the amount of the reagent to less than one equivalent.…”

“…The synthesis of fragment 5 is initiated from available compound 10, which is treated with boronating reagents (11) to obtain 4-hydroxy-1-butenyl-boronic acid (12). Then the aldehyde ( 13) is utilized to substitute boronic acid group and formed the β-unsaturated ketone, which plays as a key role in the coupling reaction below.…”

“…Then the aldehyde ( 13) is utilized to substitute boronic acid group and formed the β-unsaturated ketone, which plays as a key role in the coupling reaction below. At last, a high-valent iodine oxidant (IBX), which gives nearly 100% yield in many articles, is suitable to oxidize the hydroxy group to aldehyde and finally formed the fragment 5 (See Figure 8) [12].…”

Organohypervalent heterocycles

“…616 However, the existence of bromate impurities imparted explosive nature to IBX at elevated temperature; thus, IBX could not be developed as a potential oxidant, especially for many years until the synthetic method reported by Frigerio et al 617 Since then, IBX has been utilized in a plethora of oxidative transformations, involving the oxidation of alcohols, amines, benzylic carbon and phenols 333,[612][613][614] and oxidative cyclization to diverse heterocyclic rings has been welldocumented. 618 A. R. Katritzky and coworkers confirmed the cyclic structure of IBX derivatives by X-ray crystallographic study. 619 Martin and coworkers reported the synthesis, structure, and properties of several cyclic l 5 -iodanes in the 1980s-1990s.…”