Chi Zhang

Recyclable Hypervalent Iodine(III) Reagent Iodosodilactone as an Efficient Coupling Reagent for Direct Esterification, Amidation, and Peptide Coupling

A hypervalent iodine(III) reagent plays a novel role as an efficient coupling reagent to promote the direct condensation between carboxylic acids and alcohols or amines to provide esters, macrocyclic lactones, amides, as well as peptides without racemization. The regeneration of iodosodilactone (1) can also be readily achieved. The intermediate acyloxyphosphonium ion C from the activation of a carboxylic acid is thought to be involved in the present esterification reaction.

Design, Synthesis, Structure, and Dehydrogenation Reactivity of a Water-Soluble o-Iodoxybenzoic Acid Derivative Bearing a Trimethylammonium Group

5-Trimethylammonio-1,3-dioxo-1,3-dihydro-1λ(5)-benzo[d][1,2]iodoxol-1-ol anion (AIBX 1a), an o-iodoxybenzoic acid (IBX) derivative having the trimethylammonium moiety on its phenyl ring, possesses very good solubility in water and distinct oxidative properties from IBX, which is demonstrated in the oxidation of various β-keto esters to the corresponding dehydrogenated products using water as cosolvent. The regeneration of AIBX 1a can be easily realized from the reaction mixture due to its good water solubility.

Boron trifluoride etherate functioning as a fluorine source in an iodosobenzene-mediated intramolecular aminofluorination of homoallylic amines.

A widely used Lewis acid BF3·Et2O was shown to be capable of acting as an efficient fluorinating agent in an intramolecular aminofluorination reaction of homoallylic amines to provide 3-fluoropyrrolidines mediated by a commercially available hypervalent iodine(III) reagent PhIO at room temperature. A mechanism involving a carbocation intermediate was proposed on the basis of several experimental evidence.

A Mild and Efficient Direct α-Amination of β-Dicarbonyl Compounds Using Iodosobenzene and p-Toluenesulfonamide Catalyzed by Perchlorate Zinc Hexahydrate

A direct α-amination of β-dicarbonyl compounds has been achieved by using iodosobenzene (PhIO) as an oxidant and p-toluenesulfonamide (TsNH(2)) as an aminating reagent in the presence of a catalytic amount of perchlorate zinc hexahydrate. The present amination reaction proceeds quickly at rt (<30 min needed for most tested substrates) to provide the corresponding α-N-tosylamido β-dicarbonyl compounds in high to excellent yields.

Intramolecular Parallel [4 + 3] Cycloadditions of Cyclopropane 1,1‐Diesters with [3]Dendralenes: Efficient Construction of [5.3.0]decane and Corresponding Polycyclic Skeletons

Aiming to develop efficient and general strategies for construction of complex and diverse polycyclic skeletons, we have successfully developed [4+3]IMPC (intramolecular parallel cycloaddition) of cyclopropane 1,1-diesters with [3]dendralenes. With a combination of the [4+3]IMPC and subsequent [4+n] cycloadditions, trans-[5.3.0]decane skeleton and its corresponding structurally complex and diverse polycyclic variants could be constructed efficiently. This novel [4+3] cycloaddition reaction mode of donor-acceptor cyclopropanes proceeds as a result of the ring-strain relief of a trans-[3.3.0]octane. We strongly believe that the developed methods will demonstrate potential applications in natural products synthesis and drug discovery.

Practical Peptide Synthesis Mediated by a Recyclable Hypervalent Iodine Reagent and Tris(4-methoxyphenyl)phosphine

6-(3,5-Bis(trifluoromethyl)phenyl)-1H,4H-2aλ(3)-ioda-2,3-dioxacyclopenta[hi]indene-1,4-dione (p-BTFP-iodosodilactone, 1a) was synthesized and demonstrated to be an efficient hypervalent iodine(III) reagent for the synthesis of dipeptides from various standard amino acids, including sterically hindered amino acids, in good to high yields within 30 min in the presence of tris(4-methoxyphenyl)phosphine. In addition, the combined system of 1a/(4-MeOC6H4)3P was used to synthesize the pentapeptide leu-enkephalin in protected form. It is worth noting that 1a can be regenerated readily after reaction.

Iodosobenzene-mediated direct and efficient oxidation of β-dicarbonyls to vicinal tricarbonyls catalyzed by iron(III) salts

Iodosobenzene was found to be effective in the direct oxidation of β-dicarbonyls to vicinal tricarbonyl compounds catalyzed by Fe(NO3)·9H2O under mild and environmentally friendly conditions. Also, the present protocol was applied to the one-pot synthesis of heterocyclic compounds via vicinal tricarbonyls as the reactive intermediates. As for the reaction pathway, a plausible mechanism involving iodonium ylide, reactive carbene species and an α-hydroxylated intermediate was proposed.

Hypervalent-Iodine-Mediated Ring-Contraction Monofluorination Affording Monofluorinated Five-Membered Ring-Fused Oxazolines

The first ring-contraction monofluorination reaction mediated by a hypervalent iodine reagent is reported, and the use of the reaction for the synthesis of monofluorinated five-membered ring-fused oxazolines is described. By means of this reaction, a fluorine atom can be selectively introduced either on the five-membered ring or external to it, depending on whether or not the substrate has C-4 alkyl substituents. The reaction was used for the further conversion of probenecid and isoxepac.

Water-Soluble Hypervalent Iodine(III) Having an I–N Bond. A Reagent for the Synthesis of Indoles

A readily accessible and bench-stable water-soluble hypervalent iodine(III) reagent ( phenyl iodonio) sulfam ate (PISA) with an I-N bond was synthesized, and its structure was characterized by X-ray crystallography. With PISA, various indoles were synthesized via C-H amination of 2-alkenylanilines involving an aryl migration/intramolecular cyclization cascade with excellent regioselectivity in aqueous CH3CN. Notably, using this new method as the key step, not only two drug molecules, indometacin and zidometacin, but also another bioactive molecule, pravadoline, were synthesized.

Total Syntheses of Trichorabdal A and Maoecrystal Z

This work reports the total syntheses of Isodon diterpenes trichorabdal A and maoecrystal Z via a common bicyclo[3.2.1]octane intermediate, which chemically bridges the two distinct structures through a retro-aldol/aldol reaction cascade. Other synthetic features include an efficient cross-ring radical cyclization for rapid construction of an all carbon quaternary center commonly seen in Isodon diterpenoids, a challenging Ueno-Stork cyclization on to a sensitive 1,6-enone system, as well as a serial of chemoselective functional group manipulations in complex chemical environments.