Mirco Costa

Versatile Synthesis of Quinoline-3-Carboxylic Esters and Indol-2-Acetic Esters by Palladium-Catalyzed Carbonylation of 1-(2-Aminoaryl)-2-Yn-1-Ols

1-(2-Aminoaryl)-2-yn-1-ols, easily obtained by the Grignard reaction between 1-(2-aminoaryl)ketones and alkynylmagnesium bromides, were subjected to carbonylative conditions in the presence of the PdI2-KI catalytic system, in the presence and in the absence of an external oxidant. Under oxidative conditions (80 atm of a 4:1 mixture of CO-air, in MeOH as the solvent at 100 degrees C and in the presence of 2 mol % of PdI2 and 20 mol % of KI), 1-(2-aminoaryl)-2-yn-1-ols bearing a primary amino group were selectively converted into quinoline-3-carboxylic esters in fair to good yields [45-70%, based on starting 1-(2-aminoaryl)ketones], ensuing from 6-endo-dig cyclization followed by dehydration and oxidative methoxycarbonylation. On the other hand, indol-2-acetic esters, deriving from 5-exo-dig cyclization followed by dehydrating methoxycarbonylation, were selectively obtained in moderate to good yields [42-88%, based on starting 1-(2-aminoaryl)ketones] under nonoxidative conditions (90 atm of CO, in MeOH as the solvent at 100 degrees C and in the presence of 2 mol % of PdI2 and 20 mol % of KI), in the case of 1-(2-aminoaryl)-2-yn-1-ols bearing either a primary or secondary amino group and substituted with a bulky group on the triple bond.

Recent developments in the synthesis of heterocyclic derivatives by PdI2-catalyzed oxidative carbonylation reactions

Abstract A simple catalytic system, consisting of PdI2 in conjunction with an excess of KI, has proven to be very valuable for the direct one-step synthesis of a variety of heterocyclic derivatives by oxidative carbonylation of suitably functionalized alkynes. The same catalyst also promoted the oxidative carbonylation of β-amino alcohols to oxazolidin-2-ones with unprecedented catalytic efficiencies for this kind of reaction.

Stereoselective Synthesis of (E)‐3‐(Methoxycarbonyl)methylene‐1,3‐dihydroindol‐2‐ones by Palladium‐Catalyzed Oxidative Carbonylation of 2‐Ethynylanilines

A direct synthesis of (E)-3-(methoxycarbonyl)methylene-1,3-dihydroindol-2-ones 2 by palladium-catalyzed oxidative carbonylation of 2-ethynylanilines 1 is reported. Reactions were carried out in MeOH as the solvent at 50−70 °C in the presence of catalytic amounts of PdI2 in conjunction with KI under a 4:1 CO/air mixture (20 atm total pressure at 25 °C). When the reaction was applied to 2-alkynylanilines with internal triple bonds, the reaction course changed completely, with formation of carbamates 4.

Palladium(II) complexes containing a P, N chelating ligand Part II. Synthesis and characterisation of complexes with different hydrazinic ligands. Catalytic activity in the hydrogenation of double and triple C-C bonds

Abstract Palladium(II) complexes of the type Pd(PNO)Y (PNO = 2-(diphenylphosphino)benzaldehyde picolinhydrazone, nicotinhydrazone, isonicotinhydrazone; Y = CH3CO2, Cl, I) and Pd(PNS)Y (PNS = 2-(diphenylphosphino)benzaldehyde thiosemicarbazone; Y = CH3CO2, Cl, I) were synthesised and characterised by spectroscopic methods. The X-ray structure of an iodo complex was also determined. The catalytic activity of all the complexes in the homogeneous hydrogenation of terminal double and triple bonds was tested with particular regards to the chemoselectivity from triple to double bond. A correlation between the catalytic activity and the nature of the ligand and Y group was established. In the hydrogenation of phenylacetylene using acetato complexes as catalysts, stable phenylethynylpalladium(II) complexes were recovered and characterised by spectroscopic methods. A facile route of synthesis of alkynyl complexes was also determined.

Synthesis of 2-ynamides by direct palladium-catalyzed oxidative aminocarbonylation of alk-1-ynes

Abstract A novel synthesis of 2-ynamides (3) by palladium-catalyzed oxidative aminocarbonylation of alk-1-ynes (1) is reported. Reactions are catalyzed by PdI2/KI and are carried out at 100°C in dioxane as the solvent in the presence of dialkylamines (2) as nucleophiles (amine/alk-1-yne molar ratio=1/1) using a 4/1 CO/air mixture (20 atm total pressure at 25°C).

Combined oxidative and reductive carbonylation of terminal alkynes with palladium iodide-thiourea catalysts

Abstract Oxidative carbonylation of alkynes can be carried out catalytically in the absence of added oxidants if it is coupled with a reductive carbonylation process at the expense of the same alkyne invilved in the oxidative process. Maleic esters (from oxidative carbonylation) and unsaturated lactones (from reductive carbonylation) are the main products formed under the catalytic action of palladium iodide complexes with thiourea (tu). A complex, formally corresponding to the ionic formula [PdI(tu) 3 ]I, allows the reaction of alkylacetylenes at room temperature and atmospheric pressure. With activated alkynes such as phenylacetylene, or with alkynes containing coordinating groups, other palladium complexes with two or four molecules of thiourea are also active, although to a lesser extent. Identification of the organic by-products gives a hint of the mechanism by which coupling of oxidative and reductive carbonylation occurs.

Palladium-catalyzed synthesis of 2E-[(methoxycarbonyl)methylene]tetrahydrofurans: oxidative cyclization–methoxycarbonylation of 4-yn-1-ols versus cycloisomerization–hydromethoxylation

Abstract 4-Yn-1-ols bearing a terminal triple bond undergo oxidative cyclization–alkoxycarbonylation in methanol at 70°C and 100 atm of a 9:1 mixture of carbon monoxide and air in the presence of catalytic amounts of [PdI 4 ] 2− in conjunction with an excess of KI to give 2 E -[(methoxycarbonyl)methylene]tetrahydrofurans in good yields. A competing reaction, cycloisomerization–hydromethoxylation leading to 2-methoxy-2-methyltetrahydrofurans, can be easily curtailed by increasing the KI excess. The latter products can be prepared from 4-yn-1-ols and methanol in high yields using the same catalytic system and without KI excess in the absence of carbon monoxide.

Sensitivity-selectivity balance in mass sensors: the case of metalloporphyrins

The influence of peripheral alkyl substituents on the sensing behaviour of metalloporphyrin-based Thickness Shear Mode Resonating sensors (TSMRs) has been investigated. The presence of the alkyl chains improves the metalloporphyrin thin film permeability but at the same time increases the magnitude of non-specific interactions, reducing the influence of the intrinsic metalloporphyrin selectivity. The butyloxy derivative 2 represents a good example of a compromise between these opposite effects, where the short alkyl chain is able to increase the sensitivity and response time behaviour of the TSMR sensor, without significant loss of the selectivity properties.

Anchoring rhodium(I) on benzoylthiourea-functionalized silica xerogels. Production of recyclable hydroformylation catalysts and the crystal structure of the model compound [Rh(cod)(Hbztu)Cl]☆

Two benzoylthiourea-functionalized silica xerogels, 4.5SiO2 · SiO3/2(CH2)3NHC(S)NHC(O)Ph (XGbztu) and SiO3/2 (CH2)3NHC(S)NHC(O)Ph (XGbztu∗) have been prepared from (EtO)3Si(CH2)3NHC(S)NHC(O)Ph by the sol-gel process. They are able to bind rhodium(I) species giving the composite materials Rh/XGbztu and Rh/XGbztu∗, which are very active insoluble and recoverable catalysts for the hydroformylation of styrene. The anchored species undergo major changes during the catalytic cycles, particularly in the Rh/XGbztu system, whose iso/normal selectivity ratio gradually increaased in the first five runs. Futhermore, CH3(CH2)2NHC(S)NHC(O)Ph (HBztu) has been studied as a model of the surface binding function. The structure of [Rh(cod)(Hbztu)Cl]1, which represents a suitable molecular model for the anchored complexes, has been determined by X-ray diffraction.

Stable alkynyl palladium(II) and nickel(II) complexes with terdentate PNO and PNN hydrazone ligands

Abstract Chloro and acetato complexes of palladium(II) and nickel(II) with terdentate PNO acylhydrazonic ligands derived from 2-(diphenylphosphino)benzaldehyde have been synthesized and characterized. The acetato complexes are able to activate the CH bond of terminal alkynes, giving stable alkynyl complexes, one of which has been X-ray characterized. The coordination chemistry of the new PNN ligand 2-(diphenylphosphino)benzaldehyde 2-pyridylhydrazone (HL6) has been also investigated and the X-ray crystal structure of the complex [Pd(HL6)Cl][PdL6Cl]Cl·2H2O is reported. Starting from the nickel(II) acetato complex of HL6, it has been possible to obtain a new stable alkynyl derivative.