Iodo Groups Research Articles

Synthesis of 2-Aryloxy-1,3-dienes from Phenols and Propargyl Carbonates.

A convenient method for the synthesis of 1,3-dienes from readily available compounds is reported. 2-Aryoxy-1,3-dienes are produced stereoselectively by a nickel-catalyzed reaction of propargyl carbonates with phenols. Functional group tolerance is broad to allow iodo, formyl, and boryl groups. The resulting 1,3-dienes are of much synthetic value because they can participate in a wide variety of reactions, including the Diels-Alder reaction.

Substrate-Controlled Regioselective Iodooxygenation of Olefins

An unexpected regioselective I2/TBHP-mediated 1,2-iodo­oxygenation of alkenes with N-hydroxylamines is described. The reaction proceeds through a radical coupling mechanism or a iodonium mechanism, which is controlled by the structures of both N-hydroxylamines and alkenes, to form vicinal iodo-substituted N-alkoxyamines regioselectively. Both the iodo and alkoxyamine group of the resulting products offer rich possibilities of synthetic manipulations.

Palladium-Catalyzed Three-Component Tandem Process: One-Pot Assembly of Quinazolines.

The first example of the palladium-catalyzed, three-component tandem reaction of 2-aminobenzonitriles, aldehydes, and arylboronic acids has been developed, providing a new approach for one-pot assembly of diverse quinazolines in moderate to good yields. A noteworthy feature of this method is the tolerance of bromo and iodo groups, which affords versatility for further synthetic manipulations. Preliminary mechanistic experiments indicate that this tandem process involves two possible mechanistic pathways for the formation of quinazolines via catalytic carbopalladation of the cyano group.

Economy of Catalyst Synthesis-Convenient Access to Libraries of Di- and Tetranaphtho Azepinium Compounds.

Efficient optimization procedures in chiral catalysis are usually linked to a straightforward strategy to access groups of structurally similar catalysts required for fine-tuning. The ease of building up such ligand libraries can be increased when the structure-modifying step (introduction of a substituent) is done at a later stage of the synthesis. This is demonstrated for the extended family of di- and tetranaphtho azepinium compounds, widely used as chiral phase transfer catalysts (PTC). Using 2,6-diiodo-4,5-dihydro-3H-dinaphtho[2,1-c:1′,2′-e]azepine and 4,8-diiodo-6,7-dihydro-5H-dibenzo[c,e]azepine, respectively, as key intermediates, 18 spiro-azepinium compounds were synthesized in a total yield of 25–42% over 6–7 steps from 1,1′-binaphthyl-2,2′-dicarboxylic acid or diphenic acid, respectively. The replacement of iodo groups with aryl substituents was performed as the last or the penultimate step of the synthesis.

Sigmatropic Rearrangements of Hypervalent‐Iodine‐Tethered Intermediates for the Synthesis of Biaryls

AbstractMetal‐free dehydrogenative couplings of aryliodanes with phenols to afford 2‐hydroxy‐2′‐iodobiaryls have been developed. This reaction proceeds through ligand exchange on the hypervalent iodine atom followed by a [3,3] sigmatropic rearrangement and with complete regioselectivity. This coupling, in combination with in situ oxidation by mCPBA, enables the convenient conversion of iodoarenes into desirable biaryls. The obtained biaryls have convertible iodo and hydroxy groups in close proximity, and are thus synthetically useful, as exemplified by the controlled syntheses of π‐extended furans and a substituted [5]helicene. DFT calculations clearly revealed that the rearrangement is sigmatropic, with C−C bond formation and I−O bond cleavage proceeding in a concerted manner. Acetic acid, which was found to be the best solvent for this protocol, renders the iodine atom more cationic and thus accelerates the sigmatropic rearrangement.

Sigmatropic Rearrangements of Hypervalent-Iodine-Tethered Intermediates for the Synthesis of Biaryls.

Metal-free dehydrogenative couplings of aryliodanes with phenols to afford 2-hydroxy-2'-iodobiaryls have been developed. This reaction proceeds through ligand exchange on the hypervalent iodine atom followed by a [3,3] sigmatropic rearrangement and with complete regioselectivity. This coupling, in combination with in situ oxidation by mCPBA, enables the convenient conversion of iodoarenes into desirable biaryls. The obtained biaryls have convertible iodo and hydroxy groups in close proximity, and are thus synthetically useful, as exemplified by the controlled syntheses of π-extended furans and a substituted [5]helicene. DFT calculations clearly revealed that the rearrangement is sigmatropic, with C-C bond formation and I-O bond cleavage proceeding in a concerted manner. Acetic acid, which was found to be the best solvent for this protocol, renders the iodine atom more cationic and thus accelerates the sigmatropic rearrangement.

Synthesis and characterization of rigid rode shape homologous series: Effect of tail iodo group

GRAPHICAL ABSTRACT

Ag(I)-Catalyzed Cycloisomerization and Cyclization of Ketene Aminals: Construction of Azepine and 1,2-Dihydropyridine Derivatives

Silver-catalyzed cyclization and cycloisomerization of ketene N,N-acetals at room temperature has been developed to access a variety of highly substituted cyclobutene-fused azepine and 1,2-dihydropyridine derivatives. This cost-effective method is reliably implemented for the gram-scale synthesis of azepine and dihydropyridine derivatives. The iodo group in the periphery of the dihydropyridine motif can be functionalized with both Suzuki and Sonogashira reactions.

Hydrogen Bonding and Iodine Bonding Interactions in Sustaining Two Coordination Polymers Base on Square Grids and Tetranuclear Cobalt Clusters

Two new coordination polymers [Co(H2O)2(bpy)2]·2(Adi) (1) and [Co4(OH)2(Adi)6(bpe)2] (2) (HAdi = 4-amino-3,5-diiodobenzoic acid, bpy = 4,4′-bipyridine, bpe = 1,2-bis(4-pyridyl)ethylene) have been synthesized by methods of hydrothermal reactions and their crystal structures determined. In 1, the mononuclear Co atoms are linked by bpy ligands forming cationic two-dimensional square grids, which are connected by the intercalated Adi guest molecules through significant hydrogen-bonding interactions to give a three-dimensional supramolecular porous network with one-dimensional channels. 2 has a one-dimensional chain structure based on rhombic tetranuclear CoII clusters, connected by bpe ligands. Through special I···I interactions, adjacent chains are extended into a three-dimensional supramolecular structure. The structure versatility indicates that the amino and iodo groups of Adi ligands play a crucial role in modulating the coordination polymers. A discussion of the crystal structures, thermal stabilities, as well as the noncovalent interactions of Adi molecules is provided. IR, elemental analysis and XRPD confirmed the phase purity of the bulk materials. Magnetic properties of 2 in the 300–2 K have been discussed, which reveal the occurrence of antiferromagnetic interactions between CoII ions.

Facile Synthesis of Stereodefined α-Iodovinyl Sulfoxides, Versatile Platform to Trisubstituted Olefins

Stereodefined α-iodovinyl sulfoxides bearing a sulfinyl group and an iodo group were prepared by a one-pot iodination/Horner–Wadsworth–Emmons reaction protocol. This reaction can be applied to a wide range of aldehydes, and further application was demonstrated.

ChemInform Abstract: The Convenient Synthesis of Unsaturated Nucleoside Analogues in Water under Microwave Irradiation.

A convenient method for the regioselective synthesis of unsaturated nucleoside analogs in water under microwave irradiation was developed. All pyrimidine and purine nucleoside derivatives were exclusively alkylated at N1 and N9 respectively in good to excellent yields. In addition, this system could tolerate a broad range of functional groups, such as chloro, bromo, iodo, alkyl, amino, and hydroxyl groups. More importantly, the reaction scale could be enlarged to 50 mmol which made this route attractive for industrial application.

"Third-Generation"-Type Functional Tris(2-pyridyl)borate Ligands and Their Transition-Metal Complexes.

Phenyltris(2-pyridyl)borates (Tpyb) are a promising class of tripodal "scorpionate"-type ligands with potential utility in the development of transition-metal complexes with interesting optical, electronic, or magnetic properties and as building blocks to metallosupramolecular polymers. We report here a new class of "third-generation"-type Tpyb ligands that contain different functional groups attached to the boron-bound aryl moiety. The synthesis, characterization, and metal-ion complexation behavior of ligands with iodo and trimethylsilyl groups are discussed. The electrochemical and absorption characteristics of the corresponding low-spin iron(II) and ruthenium(II) complexes are compared. We demonstrate the further elaboration of iodo derivatives with alkynes via Sonogashira-Hagihara coupling, a process that proceeds with high yield for the iron(II) and ruthenium(II) complexes but not for the free ligand. Borylation of the silyl-substituted ruthenium(II) complex with BBr3 was also investigated. In addition to the expected borylation product Ru(Tpyb-Bpin)2, the replacement of one (major product) or two phenyl groups is observed, suggesting that electrophilic borylation occurs at both the C(Ph)-Si and the C(Ph)-B aromatic carbon atoms. The successful attachment of a range of different functional groups at the periphery of the Tpyb metal complexes is expected to provide opportunities to access new polymeric materials via C-C coupling or click-type reactions.

Modular Approach to 9-Monosubstituted Fluorene Derivatives Using Mo(V) Reagents.

Oxidative coupling using molybdenum(V) reagents provides fast access to highly functionalized 9-monosubstituted fluorenes. This synthetic approach is highly modular, is high yielding, and tolerates a variety of labile moieties, e.g. amides or iodo groups. The established protocol leads to promising precursors for pharmacologically important analogues of melatonin.

The Convenient Synthesis of Unsaturated Nucleoside Analogues in Water under Microwave Irradiation

ABSTRACTA convenient method for the regioselective synthesis of unsaturated nucleoside analogs in water under microwave irradiation was developed. All pyrimidine and purine nucleoside derivatives were exclusively alkylated at N1 and N9 respectively in good to excellent yields. In addition, this system could tolerate a broad range of functional groups, such as chloro, bromo, iodo, alkyl, amino, and hydroxyl groups. More importantly, the reaction scale could be enlarged to 50 mmol which made this route attractive for industrial application.

Indium‐Catalyzed Reductive Sulfid­ation of Esters by Using Thiols: An Approach to the Diverse Synthesis of Sulfides

AbstractA new reductive preparation of unsymmetrical sulfides from esters and thiols in the presence of InI3 and either 1,1,3,3‐tetramethyldisiloxane (TMDS) or PhSiH3 as the reductant was developed. This protocol was applied to not only benzoic acid esters that have a methoxy, methyl, chloro, bromo, iodo, or trifluoromethyl group on the aromatic ring but also aliphatic acid esters with either aromatic or aliphatic thiols. A reaction mechanism is proposed by using Hammett plot results and several control experiments.

The impact of modular substitution on crystal packing: the tale of two ureas

A small library of 13 (3a–m) compounds with modular positioning of iodide and urea/thiourea groups was synthesized in excellent yields in a single step synthetic protocol. The existence of the anticipated (thio)urea derivatives was unambiguously established using a combination of 1–2D NMR spectroscopy, ESI-MS and single crystal X-ray diffraction studies. These (thio)urea compounds were classified into four classes as follows: a) mono-substituted urea, b) di-substituted urea, c) di-substituted thiourea and d) electronically tailored di-substituted thiourea. The changes in molecular conformation and crystal packing due to the change in the relative positioning of the iodo group at the phenyl ring attached to one of the N atoms and different substituents at other N atoms in urea and thiourea derivatives have been discussed. The urea derivatives, in general, display the chain association through one-dimensional three-centered N–H⋯O hydrogen bonding interactions due to the trans–trans orientation of both NH protons with respect to the carbonyl group, whereas the thiourea compounds exhibit a centrosymmetric dimeric assembly via the complementary N–H⋯S interactions because of the trans–cis arrangement of the NH protons leading to either a helical or a sheet pattern. The presence of a nitro group at the para position of the thiourea derivative leads to trans–trans arrangement of both NH protons with respect to the thiocarbonyl groups, thus yielding a chain assembly through one-dimensional three-centered N–H⋯S interactions similar to urea derivatives. Associations of these chains or sheets in urea/thiourea derivatives through halogen bonding interactions (hal⋯hal, hal⋯π, hal⋯S etc.) generate a 2D assembly.

Stereochemical properties of N-benzoylated carbazole derivatives

The atropisomeric properties of 2′,6′-disubstituted N-benzoylated carbazole derivatives were investigated. It was found that the bulky t-butyl and iodo groups restricted rotation about the N–C7′ and C7′–C1′ bonds to separate four stereoisomers, in which rotation about the C7′–C1′ bond was in perfect concert with rotation about the N–C7′ bond. The relation of the rotation of the N–C7′ and C7′–C1′ axes was investigated by comparing the stereochemistry of variously 2′,6′-disubstituted N-benzoyl-carbazole derivatives. It was suggested that the concerted rotation of the N–C7′ and C7′–C1′ axes might occur even in less hindered compounds.

Poly-iodinated closo 1,2-C2B10 and nido [7,8-C2B9]− carborane frameworks: Synthesis and consequences

The preparation of Cc-monosubstituted closo and nido carborane derivatives, mono-, di and tetraiodinated is reported. Some of these mono-to poly-iodinated nido carboranes are studied in terms of the acidity of the open face bridging proton, their chemical shift position in the 1H NMR, and the lesser tendency to η5-coordination in parallel to a larger number of iodo groups.

1,3-Diiodocalix[4]arene: synthesis by Ullmann-type iodination of 1,3-bistriflate ester of calix[4]arene, conformational analysis, and transformation into 1,3-dicarboxy-, diformyl-, and dialkylcalix[4]arenes.

A facile synthesis of 1,3-diiodocalix[4]arene 6 has been achieved by copper-catalyzed iodination of the 1,3-bistriflate ester 2a of p-tert-butylcalix[4]arene. After protection of the hydroxy groups with iodomethane, diiodide 6 is subjected to halogen–lithium exchange with butyllithium, followed by carbonation with CO2 or formylation with N-formylpiperidine and subsequent deprotection of the hydroxy groups to give novel dicarboxylic acid 11 or dialdehyde 16 in practical yields. The iodo groups of diiodide 6 pass through the calixarene macrocycle; the activation free energy for the conversion of the more stable syn conformer 6syn to the less stable anti conformer 6anti is ΔG(⧧) = 104 kJ mol(–1) at 298 K. Dialdehyde 16 shows fast self-exchange between two equivalent species with a cone conformation, ΔG(⧧), being 63.2 kJ mol(–1). Dicarboxylic acid 11 adopts a cone conformation and forms a dimer in solution as suggested by 1H NMR and X-ray crystallographic analyses. The arrangement of the iodide groups of compound 6 can be fixed predominantly to anti (17a and 17b) by introducing bulky alkyl groups (e.g., propyl groups) onto the hydroxy groups. The stereospecific alkylation of the iodo groups of the resulting di-O-alkylated anti-1,3-diiodides provides access to the anti-1,3-dialkylcalixarenes 19, which is otherwise difficult to obtain.

Regioselective synthesis of thiophene fused sultam derivatives via iodocyclization approach and their application towards triazole linker

An efficient regioselective synthesis of 4-iodo-2,3-disubstituted-2H-thieno[3,2-e][1,2]thiazine-1,1-dioxide derivatives via iodocyclization approach using iodine under mild reaction condition described herein. This coupling–iodocyclization strategy tolerated a variety of functional groups such as alkyl, cycloalkyl, phenyl producing the six-membered heterocyclic ring selectively. The resulting 4-iodo-2,3-disubstituted-2H-thieno[3,2-e][1,2]thiazine-1,1-dioxide was coupled with a variety of boronic acids (Suzuki coupling) and activated alkenes (Heck coupling). The iodo group was utilized for Sonogashira coupling followed by efficient transformation to azido precursor, which was used for the synthesis of various thieno-sultam linked with triazole.