Microwave-assisted base-free synthesis of trans-cinnamic acids using hypervalent iodonium salts

A fast and convenient base-free Heck reaction of acrylic acid with hypervalent iodonium salts was achieved under microwave irradiation in water, providing a simple method for the synthesis of trans-cinnanfic acids in good yields in short time.

Chemoselective synthesis of α-carboline derivatives via hypervalent iodine-catalyzed [3+3] annulation under metal-free conditions

A strategy for the synthesis ofα-carboline derivatives from indole-3-carboxaldehydes and 3-aminocyclohex-2-enones under metal-free conditions has been developed.The combination use of phenyliodine(Ⅲ)diacetate(PIDA)and benzoic acid could significantly facilitate the corresponding[3+3]annulation process.This newly developed strategy featured unextraordinary chemoselectivity,good functional group tolerance and the preservation of the carbonyl group of the ketone substrates,which offers the possibility for further transformation of the products.

An environmentally benign benzylic oxidation catalyzed by hypervalent iodine intermediate in water

An effective and environmentally benign benzylic oxidation for transition of alkylarenes into the corresponding carbonyl compounds was reported. Alkylarenes were mixed and stirred with potassium bromide, m-chloroperbenzoic acid and a catalytic amount of iodobenzene in water at 60 ℃ for several hours, a series of the corresponding carbonyl compounds was obtained in moderate to good yields. In the reaction, iodobenzene was first oxidized by m-chloroperbenzoic acid into the hypervalent iodine intermediate which then reacted with potassium bromide to form the key radical initiator for the benzylic oxidation.

Hypervalent Iodine(Ⅲ)-Mediated Benzannulation of Enamines with Alkynes: an Efficient Synthesis of Substituted Aminonaphthoic Acid Derivatives

An intermolecular two C-C bond formation procedure for the synthesis of carbocycles mediated by hyperva-lent iodine(III)reagents was developed.This metal free protocol provided a new approach for the synthesis of use-ful substituted 1-amino-2-naphthoic acid derivatives via benzannulation reactions.Various N-unsubstituted and N-alkyl substituted aromatic enamines with terminal alkynes and non-terminal alkynes can be converted into corre-sponding 1-amino-2-naphthoic acid derivatives under mild reaction conditions.When meta-substituted phenyl enamines were employed in the reaction,two cyclization paths were detected in the reaction and ortho-cyclization products were the only or major products.Good functional group tolerance,readily available material and high atom utilization efficiency make this method a potential procedure which may find broad application in organic synthesis.

Hypervalent iodine-mediated gem-difluorination of vinyl halides enabled by exclusive 1,2-halo migration

β-Difluorinated alkyl halides are of significant value in the modular synthesis of gem-difluorinated molecules.An exclusive 1,2-halo migratory gem-difluorination of vinyl halides with in situ-generated PhIF_(2)·HF is described.This protocol provides a general and practical approach towards a wide variety ofβ-difluorinated alkyl bromides.Bothα-andβ-bromoalkyl alkenes are suitable substrates,leading to two distinct types of products.The extension of this protocol to vinyl chloride and iodide are also feasible.The synthetic versatility of this method has been highlighted by the late-stage modification of complex small molecules and further transformations of theβ-difluorinated alkyl halides to valuable CF_(2)-containing compounds.

Hypervalent iodine mediated C-H amination of quinoxalinones with heteroaromatic amines under metal-free conditions

An efficient and facile method for C-H amination of quinoxalinones with heteroaromatic amines under metal-free conditions has been described.In the presence of hypervalent PIDA reagent,the desired products with various groups were obtained with moderate to high yields.

Improvement of the Lewis-Abegg-Octet Rule Using an “Even-Odd” Rule in Chemical Structural Formulas: Application to Hypo and Hyper-Valences of Stable Uncharged Gaseous Single-Bonded Molecules with Main Group Elements

As Lewis proposed his octet rule, itself inspired by Abegg’s rule, that a molecule is stable when all its composing atoms have eight electrons in their valence shell, it perfectly applied to the vast majority of known stable molecules. Only a few stable molecules were known that didn’t fall under this rule, such as PCl5 and SF6, and Lewis chose to leave them aside at the time of his research. With further advances in chemistry, more exceptions to this rule of eight have been found, usually with the central atom of the structure having more or less than eight electrons in its valence shell. Theories have been developed in order to modify the octet rule to suit these molecules, defining these as hyper- or hypo-valent molecules and using other configurations for the electrons. The present paper aims to propose a representation rule for gaseous single-bonded molecules that makes it possible to reconcile both;molecules following the octet theory and those which do not. In this representation rule, each element of the molecule is subscripted with two numbers that follow a set of simple criteria. The first represents the number of valence electrons of the element;while the second is calculated by adding the first number to the number of the element’s covalent bonds within the molecule. The latter is equal to eight for organic molecules following the octet rule. Molecules being exceptions to the octet rule are now encompassed by this new even-odd rule: they have a valid chemical structural formula in which the second number is even but not always equal to eight. Both rules—octet and even-odd—are discussed and compared, using several well-known gaseous molecules having one or several single-bonded elements. A future paper will discuss the application of the even-odd rule to charged molecules.

1,3-Dipolar Cycloaddition of Polycyclic Aromatic Azomethine Ylides and Alkynylbenziodoxoles for Synthesis of Functional Dibenzoullazines

A new family of dibenzoullazine derivatives was synthesized through 1,3-dipolar cycloaddition of polycyclic aromatic azomethine ylides with alkynylbenziodoxoles followed by oxidation.The benziodoxole moiety in the resulting products was used as a versatile linchpin for the synthesis of structurally diverse functional dibenzoullazines that are difficult to access by other synthetic methods.

Metal-free nucleophilic 7,8-dearomatization of quinolines:Spiroannulation of aminoquinoline protected amino acids

Atom-and step-economy in IBX assisted diversity-oriented synthesis is achieved with a versatile AQ auxiliary α-amino acid analogs offering rapid access to polycyclic spiro-quinolines featuring a quaternary stereocenter in 20%–91% yields under mild conditions via 7,8-dearomatization of quinolines. Free of a preinstalled activation group is highlight of this intramolecular oxidation spiroannulation tandem reaction. This type of N-heterospirocycles, traditionally difficult to access, may open the door to a potentially interest scaffold for synthetic and medicinal chemistry.

Fluoroalcohol-mediated reductive iodonio-Claisen rearrangement： Synthesis of complex ortho-substituted-allyl iodoarenes

Reductive iodonio-Claisen rearrangement （RICR） involving 23-iodanes and allyl or substituted-allyl silanes in fluoroalcohols, such as 1,1,1,3,3,3-hexafluoroi- sopropanol （HFIP） and 2,2,2-trifluoroethanol （TFE）, was studied for the synthesis of complex ortho-allyl or substituted-allyl iodoarenes. In comparison to the pre- viously reported condition involving boron trifluoride diethyl etherate, the RICR mediated by fluoroalcohols was found to proceed more effectively. The resulting complex ortho-allyl iodoarenes are useful synthetic intermediates and can be readily converted to various heterocyclic compounds.

Pentafluoroethylbenziodoxole （BIX-C2Fs）： A Shelf-Stable Reagent for Pentafluoroethylation of β-Ketoesters and Arylboronic Acids

An improved method for the preparation of pentafluoroethylating reagent pentafluoroethyl-substituted benzio- doxole （BIX-C2Fs） was described. Under mild conditions, BIX-C2F5 was able to react with β-ketoesters or aryl/ heteroaryl boronic acids to generate pentafluoroethylated compounds in good yields.

Synthesis of Diverse Aryliodine(Ⅲ)Reagents by Anodic Oxidationt

Main observation and conclusion An anodic oxidation enabled synthesis of hypervalent iodinel(Ⅲ)reagents from aryl iodides is demonstrated.Under mild electrochem-ical conditions,a range of arylidine(Ⅲ)reagents including iodosylarenes,(difunctionaliodo)arenes,benziodoxoles and diaryliodoni-um salts can be efficiently synthesized and derivatized in good to excellent yields with high selectivity.As only electrons serve as the oxidation reagents,this method offers a more straightforward and sustainable manner avoiding the use of expensive or hazardous chemical oxidants.

Synthesis of polycyclic spiro-fused indolines via IBX-mediated cascade cyclization

We report a 2-iodoxybenzoic acid(IBX)-mediated intarmolecular oxidative spiro-fused tandem cyclization reaction of tryptophan analogs bearing an N-arylamides side-chain to rapidly afford polycyclic spiroindolines featuring multiple stereocenters including a quaternary stereocenters under mild reaction conditions.Among them,a novelty azaphosphol idine-containing spiroindoline compound is synthesized for the first time.It may open the door to azaphos pholidine-containing spiroindoline compound of potential interest in synthetic and medicinal chemistry.A plausible mechanism is proposed.

An efficient chlorination of aromatic compounds using a catalytic amount of iodobenzene

An efficient method was developed for chlorination of aromatic compounds with electron-donating groups using iodobenzene as the catalyst and m-chloroperbenzoic acid as the terminal oxidant in the presence of 4-methylbenzenesulfonic acid in THF at room temperature for 24 h,and a series of the monochlorinated compounds was obtained in good yields.In this protocol,the catalyst iodobenzene was first oxidized into the hypervalent iodine intermediate,which then treated with lithium chloride and finally reacted with aromatic compounds to form the chlorinated compounds.

Double dehydrogenation of carbocyclic β-dicarbonyl compounds:Koser's reagent can do what iodine(V) reagents can

Koser's reagent is found to be effective in the oxidative double dehydrogenation of various carbocyclic β-dicarbonyl compounds,which constitutes the first example on dehydrogenation reactivity of hypervalent iodine(Ⅲ) reagents for carbocyclic carbonyl compounds. DFT calculations reveal that the rate-determining step is the electrophilic addition of PhI+OH onto enolate of monodehydrogenated product.

Skeletal contraction:A novel strategy to access multisubstituted cyclobutane

The polysubstituted and spirocyclic cyclobutanes were efficiently constructed by the utilization of a novel skeletal contraction strategy which only took one-step synthesis from the readily accessible pyrrolidines.The mechanistic studies indicated that a key intermediate N-aminated pyrrolidine was formed initially and subsequent extrusion of a nitrogen via a radical pathway completed the transformation.This practical methodology was further highlighted by the concise,formal synthesis of the cytotoxic natural product piperarborenine B.