First hypervalent iodine(iii)-catalyzed C–N bond forming reaction: catalytic spirocyclization of amides to N-fused spirolactams

Abstract

A protic solvent, 2,2,2-trifluoroethanol (CF(3)CH(2)OH), was successfully introduced into hypervalent iodine(III)-involved catalytic cycles as an effective solvent, and the first iodoarene-catalyzed intramolecular carbon-nitrogen bond forming reaction was achieved under strong acid-free and mild conditions.

Recycling and Catalytic Approaches for the Development of a Rare-Metal-Free Synthetic Method Using Hypervalent Iodine Reagent

“…Thus this spirolactam-forming method developed by us is the first and only example to utilize the catalytic strategy for performing effective carbon-nitrogen bond-forming reactions using iodoarenes as organocatalysts to provide the key intermediates of naturally occurring alkaloids. 19) …”

“…[11][12][13][14][15][16][17] By applying the unique regeneration method of the recyclable reagents 1, we next succeeded in the catalytic use of hypervalent iodine reagents, which led to the effective utilization of the reagents as "organocatalysts." [18][19][20][21] Furthermore, we challenged the asymmetric oxidations as being very difficult with hypervalent iodines and have achieved the highly selective catalytic oxidations of phenols for the first time by designing a new chiral reagent 2Ј. 22) Through such research, the possibility of hypervalent iodines as environmentally friendly alternatives not only to heavymetal oxidants but also even to rare metals became realistic.…”

Efficient Synthesis of p-Quinols Using Catalytic Hypervalent Iodine Oxidation of 4-Arylphenols with 4-Iodophenoxyacetic Acid and Oxone

“…30) Moreover, the solubility of 3 in alkaline solution makes its separation and recovery steps easier to carry out without a purification step. As part of our study for development of catalytic hypervalent iodine oxidations, [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] we report herein an efficient synthesis of p-quinols directly from 4-arylphenols using catalytic amount of 3 and Oxone ® in tetrahydrofuran (or 1,4-dioxane)-water (Chart 2). We first examined 4-phenylphenol (1a) as a model substrate ( Table 1).…”

Speedy and Clean Hypervalent Iodine/Nitroxyl Radical Mediated Oxidation of Alcohols Using Recyclable Adamantane Reagent with Highly Active 2-Azaadamantane-<i>N</i>-oxyl Organocatalyst

“…Furthermore, the reagent could be nearly quantitatively recovered after the reactions by utilizing the insolubility of the formed tetraiodide 1′ in a polar solvent, specifically, methanol. Based on these significant advantages, the adamantane reagent 1 would serve as a recyclable and greener alternative to conventionally-used hypervalent iodine reagents, and mediate many types of oxidation reactions with efficiencies similar to those of phenyliodine diacetate (PIDA), [29][30][31][32][33][34][35][36] while the workup for the recovery of the reagent usually requires three separate steps, that is, i) evaporation of the reaction solvent, ii) precipitation by adding methanol, and then iii) filtering.Hence, the procedure to recover the tetraiodide 1′ started with the removal of the dichloromethane solvent under reduced pressure by a rotary evaporator, and the tetraiodide 1′ should be then precipitated by adding methanol to the resulting residue. Aimed at realizing a more practical procedure for the hypervalent iodine/nitroxyl radical oxidation of alcohols, we have further designed a more simplified and faster system that can skip the above mentioned precipitation steps, i) and ii), which are reported in this paper (Chart 1).…”

“…Furthermore, the reagent could be nearly quantitatively recovered after the reactions by utilizing the insolubility of the formed tetraiodide 1′ in a polar solvent, specifically, methanol. Based on these significant advantages, the adamantane reagent 1 would serve as a recyclable and greener alternative to conventionally-used hypervalent iodine reagents, and mediate many types of oxidation reactions with efficiencies similar to those of phenyliodine diacetate (PIDA), [29][30][31][32][33][34][35][36] while the workup for the recovery of the reagent usually requires three separate steps, that is, i) evaporation of the reaction solvent, ii) precipitation by adding methanol, and then iii) filtering.…”