Palladium(II)-Mediated Addition of Benzenediamines to Isocyanides: Generation of Three Types of Diaminocarbene Ligands Depending on the Isomeric Structure of the Nucleophile

Coupling of the palladium-bis­(isocyanide) complexes <i>cis</i>-[PdCl₂(CNR)₂] (R = 2,6-Me₂C₆H₃ <b>1</b>, 2-Cl-6-MeC₆H₃ <b>2</b>) with benzene-1,3-diamine (<b>BDA1</b>) leads to the diaminocarbene species <i>cis</i>-[PdCl₂(CNR)­{C­(NHR)NH­(1,3-C₆H₄NH₂)}] (<b>5</b> and <b>6</b>, respectively). In this reaction, <b>BDA1</b> behaves as a monofunctional nucleophile that adds to one of the RNC ligands by one amino group. By contrast, the reaction of <b>1</b> and <b>2</b> with benzene-1,4-diamine (<b>BDA2</b>) involves both amino functionalities of the diamine and leads to the binuclear species [<i>cis</i>-PdCl₂(CNR)­{μ-<u>C</u>­(NHR)NH­(1,4-C₆H₄)­NH<u>C</u>­(NHR)}<i>-</i>(<i>cis</i>)-PdCl₂(CNR)] (<b>6</b> and <b>7</b>) featuring two 1,4-bifunctional diaminocarbene ligands. The reaction of <i>cis</i>-[PdCl₂(CNR)₂] (R = cyclohexyl <b>3</b>) with either <b>BDA1</b> or <b>BDA2</b> does not afford any isolable carbene derivatives. The most versatile chemistry was observed when <b>1</b>–<b>3</b> were treated with benzene-1,2-diamine (<b>BDA3</b>) and the relevant substituted 1,2-diamines, viz., 4,5-dimethylbenzene-1,2-diamine (<b>BDA4</b>) and 4,5-dichlorobenzene-1,2-diamine (<b>BDA5</b>). The addition of these diamines brings about the formation of the monocarbene cationic complexes <i>cis</i>-[PdCl­(CNR)­{<u>C</u>­(NHR)NHC₆H₂X₂<u>N</u>H₂}]Cl (X = H, Me, Cl) (<b>8</b>–<b>16</b>), the Chugaev-type <i>C,C</i>-bound bis-carbenes <i>cis</i>-[PdCl₂{<u>C</u>­(NHR)NHC₆H₂X₂NH<u>C</u>­(NHR)}] (<b>17</b>, <b>18</b>), and the bis­(<i>C,N</i>-chelated)­carbene complexes <i>cis</i>-[Pd­{<u>C</u>­(NHR)NHC₆H₂X₂<u>N</u>H₂}₂]­Cl₂ (<b>19</b>–<b>24</b>). All prepared complexes (with the exception of <b>17</b> and <b>18</b>) were isolated as colorless or pale yellow solids and characterized by elemental analyses (C, H, N), HRESI^±-MS, IR, ¹H and ¹³C­{¹H} NMR spectroscopies, and <b>4</b>, <b>7</b>, <b>13</b>, <b>16</b>, and <b>24</b> by X-ray diffraction. Complexes <b>17</b> and <b>18</b> were characterized by HRESI^±-MS and IR spectroscopy, and their structures were established by X-ray crystallography

Application of palladium complexes bearing acyclic amino(hydrazido)carbene ligands as catalysts for copper-free Sonogashira cross-coupling

Metal-mediated coupling of one isocyanide in cis-[PdCl2(CNR1)2] (R1 = C6H11 (Cy) 1, tBu 2, 2,6-Me2C6H3 (Xyl) 3, 2-Cl-6-MeC6H34) and various carbohydrazides R2CONHNH2 [R2 = Ph 5, 4-ClC6H46, 3-NO2C6H47, 4-NO2C6H48, 4-CH3C6H49, 3,4-(MeO)2C6H310, naphth-1-yl 11, fur-2-yl 12, 4-NO2C6H4CH213, Cy 14, 1-(4-fluorophenyl)-5-oxopyrrolidine-3-yl 15, (pyrrolidin-1-yl)C(O) 16, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propane-1-yl 17, EtNHC(O) 18] or sulfohydrazides R3SO2NHNH2 [R3 = Ph 19, 4-MeC6H420] led to a series of (hydrazido)(amino)carbene complexes cis-[PdCl2{C(NHNHX)double bond; length as m-dashN(H)R1}(CNR1)]; X = COR2, SO2R3 (21–48, isolated yields 60–96%). All prepared species were characterized by elemental analyses (C, H, N), HR ESI+-MS, IR, 1H and 13C{1H} NMR spectroscopy, and by a single-crystal X-ray diffraction for 38. Complexes 21–48 demonstrated excellent activity as catalysts in copper-free Sonogashira coupling of aryl iodides and a variety of aromatic terminal alkynes. Catalytic system runs in environmentally benign EtOH ensuring product yields of up to 75–96% and TONs of up to 104. Mechanism of the copper-free Sonogashira catalytic cycle involving 21–48 as catalysts was proposed upon identification of key intermediates using HRESI-mass

Facile Gold-Catalyzed Heterocyclization of Terminal Alkynes and Cyanamides Leading to Substituted 2‑Amino-1,3-Oxazoles

Facile gold-catalyzed heterocyclization based upon intermolecular trapping of the generated α-oxo gold carbenes with various cyanamides R²R³NCN (R²/R³ = Alk/Alk, −(CH₂)₂O­(CH₂)₂–, Ar/Ar, Ar/H) has been developed. In most cases, 2-amino-1,3-oxazoles functionalized at the nitrogen atom as well as at the fifth position of the heterocyclic ring (12 examples) were isolated in good to moderate yields

Molecular Switching through Chalcogen-Bond-Induced Isomerization of Binuclear (Diaminocarbene)Pd^II Complexes

Binuclear diaminocarbene complexes, which form as a regioisomer mixture in the reaction between isocyanide–palladium(II) complex cis-[PdCl2(CNXyl)2] and 1,3-thiazol-2-amine, are able to exchange an anionic chloride ligand with other halides, such as Br or I. This process also affords binuclear complexes as mixtures of kinetically and thermodynamically controlled regioisomers. In CDCl3 solutions, we observed interconversion of kinetically and thermodynamically controlled regioisomers. The results of the DFT calculations revealed that in CHCl3 solution, each pair of the isomers exhibited two different types of chalcogen bonding such as S···X or S···N; the presence of CBs for two complexes in the solid state was also proven through X-ray crystallographic study. Based on the combined experimental and theoretical data, it could be concluded that thermodynamic favorability for the formation of thermodynamically controlled regioisomers increases in the Cl < Br ≈ I row and correlate well with the energy difference between S···N and S···X (X = Cl, Br, I) chalcogen bonds in kinetically and thermodynamically controlled products. This means that it is possible to change the structure of metallocycles in binuclear diaminocarbene complexes by simply replacing one halide ligand with another

Synthesis of 3-(Pyridin-2-yl)quinazolin-2,4(1<i>H,</i>3<i>H</i>)-diones via Annulation of Anthranilic Esters with <i>N</i>-pyridyl Ureas

A new route for the synthesis of quinazolin-2,4(1H,3H)-diones and thieno [2,3-d]pyrimidine-2,4(1H,3H)-diones substituted by pyridyl/quinolinyl moiety in position 3 has been developed. The proposed method concluded in an annulation of substituted anthranilic esters or 2-aminothiophene-3-carboxylates with 1,1-dimethyl-3-(pyridin-2-yl) ureas. The process consists of the formation of N-aryl-N′-pyridyl ureas followed by their cyclocondensation into the corresponding fused heterocycles. The reaction does not require the use of metal catalysts and proceeds with moderate to good yields (up to 89%). The scope of the method is more than 30 examples, including compounds with both electron-withdrawing and electron-donating groups, as well as diverse functionalities. At the same time, strong electron-acceptor substituents in the pyridine ring of the starting ureas reduce the product yield or even prevent the cyclocondensation step. The reaction can be easily scaled to gram quantities

Metal-Mediated and Metal-Catalyzed Reactions of Isocyanides

Metal-Mediated and Metal-Catalyzed Reactions of Isocyanide

Coupling of Thiazole-2-Amines with Isocyanide Ligands in <i>bis</i>-(Isocyanide) Platinum Complex: A New Type of Reactivity

The treatment of cis-[PtCl2(XylNC)2] with thiazol-2-amines in a 2:1 ratio leads to a regioisomeric mixture of two binuclear complexes. These regioisomers are products of kinetic and thermodynamic control capable of regioisomerization. When the same reaction is carried out with a 5-fold excess of thiazol-2-amine, the nucleophile is able to react with the in situ-formed binuclear platinum(II) complexes, yielding a new type of bis-carbene platinum species. All new isolated compounds were characterized by 1H, 13C{1H}, and 195Pt{1H} NMR spectroscopy, high-resolution ESI-MS, and single-crystal X-ray diffraction

Intra-/Intermolecular Bifurcated Chalcogen Bonding in Crystal Structure of Thiazole/Thiadiazole Derived Binuclear (Diaminocarbene)PdII Complexes

The coupling of cis-[PdCl2(CNXyl)2] (Xyl = 2,6-Me2C6H3) with 4-phenylthiazol-2-amine in molar ratio 2:3 at RT in CH2Cl2 leads to binuclear (diaminocarbene)PdII complex 3c. The complex was characterized by HRESI+-MS, 1H NMR spectroscopy, and its structure was elucidated by single-crystal XRD. Inspection of the XRD data for 3c and for three relevant earlier obtained thiazole/thiadiazole derived binuclear diaminocarbene complexes (3a EYOVIZ; 3b: EYOWAS; 3d: EYOVOF) suggests that the structures of all these species exhibit intra-/intermolecular bifurcated chalcogen bonding (BCB). The obtained data indicate the presence of intramolecular S•••Cl chalcogen bonds in all of the structures, whereas varying of substituent in the 4th and 5th positions of the thiazaheterocyclic fragment leads to changes of the intermolecular chalcogen bonding type, viz. S•••π in 3a,b, S•••S in 3c, and S•••O in 3d. At the same time, the change of heterocyclic system (from 1,3-thiazole to 1,3,4-thiadiazole) does not affect the pattern of non-covalent interactions. Presence of such intermolecular chalcogen bonding leads to the formation of one-dimensional (1D) polymeric chains (for 3a,b), dimeric associates (for 3c), or the fixation of an acetone molecule in the hollow between two diaminocarbene complexes (for 3d) in the solid state. The Hirshfeld surface analysis for the studied X-ray structures estimated the contributions of intermolecular chalcogen bonds in crystal packing of 3a–d: S•••π (3a: 2.4%; 3b: 2.4%), S•••S (3c: less 1%), S•••O (3d: less 1%). The additionally performed DFT calculations, followed by the topological analysis of the electron density distribution within the framework of Bader’s theory (AIM method), confirm the presence of intra-/intermolecular BCB S•••Cl/S•••S in dimer of 3c taken as a model system (solid state geometry). The AIM analysis demonstrates the presence of appropriate bond critical points for these interactions and defines their strength from 0.9 to 2.8 kcal/mol indicating their attractive nature

Rhodamine spiroamides for multicolor single-molecule switching fluorescent nanoscopy

The design, synthesis, and evaluation of new rhodamine spiroamides are described. These molecules have applications in optical nanoscopy based on random switching of the fluorescent single molecules. The new markers may be used in (co)localization studies of various objects and their (mutual) positions and shape can be determined with a precision of a few tens of nanometers. Multicolor staining, good photoactivation, a large number of emitted photons, and selective chemical binding with amino or thiol groups were achieved due to the presence of various functional groups on the rhodamine spiroamides. Rigidized sulfonated xanthene fragment fused with six-membered rings, N,N′-bis(2,2,2-trifluoroethyl) groups, and a combination of additional double bonds and sulfonic acid groups with simple aliphatic spiroamide residue provide multicolor properties and improve performance of the rhodamine spiroamides in photoactivation and bioconjugation reactions. Having both essential parts of the photoswitchable assembly - the switching and the fluorescent (reporter) groups - combined in one chemical entity make this approach attractive for further development. A series of rhodamine spiroamides is presented along with characterizations of their most relevant properties for application as fluorescent probes in single-molecule switching and localization microscopy. Optical images with resolutions on the nanometer scale illustrate the potential of the labels in the colocalization of biological objects and the two-photon activation technique with optical sectioning.Fil: Belov, Vladimir N.. Max Planck Institute for Biophysical Chemistry; AlemaniaFil: Bossi, Mariano Luis. Max Planck Institute for Biophysical Chemistry; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Fölling, Jonas. Max Planck Institute for Biophysical Chemistry; AlemaniaFil: Boyarskiy, Vadim P.. Max Planck Institute for Biophysical Chemistry; Alemania. St. Petersburg State University; RusiaFil: Hell, Stefan W.. Max Planck Institute for Biophysical Chemistry; Alemani