Andrea Penoni

Catalytic amination of unsaturated hydrocarbons : reactions of p-nitrophenylazide with alkenes catalysed by metallo-porphyrins

Abstract Porphyrin derivatives of transition metals such as Ru(TPP)CO, Ru(OEP)CO and Co(OEP)(TPP=dianion of 5, 10, 15, 20-tetraphenylporphyrin, OEP=dianion of 2, 3, 7, 8, 12, 13, 17, 18-octaetylporphyrin) catalyse the reaction of p-nitrophenylazide with cyclohexene to give the corresponding allylamine in good yields. With other olefins such as cyclooctene, 1-octene, styrene and substituted styrenes the main product becomes the corresponding aziridine. The reaction of p-nitrophenylazide with Ru(TPP)CO has been investigated and the mechanism of the catalytic reactions is discussed.

Synthesis of Indole Derivatives with Biological Activity by Reactions Between Unsaturated Hydrocarbons and N-Aromatic Precursors

The present review is devoted to illustrate the state of the art of the syntheses of indoles, focusing particularly on the most recent developments of new synthetic approaches. Emphasis is given to the preparation of natural products or bioactive compounds containing the indole unit. We present a historical perspective of indole synthesis showing the strategies by choosing the nitrogen precursors. The review is organized sharing the indole synthetic approaches by using different nitrogen-containing functional groups in aromatic substrates used as source of the nitrogen of the indole moiety. Some functional groups and some typical reactions are particularly stressed and highlighted because of the limited coverage given in previous reviews published on this topic. Other synthetic approaches more used and discussed in recent, complete and excellent reviews on the topic are summarized but the most recent published results are highlighted. Our interest is particularly focused on the indolization procedures and on the different methods used for the ring closure and no attention is given to modification of indole structures starting from molecules with a preformed indole unit. Intriguing indole syntheses are continually discovered and the importance that the scientific community gives to these new developments is connected with the strategic role of molecules containing the indole unit. Indoles are the class of heterocycles with more applications and extensive interest due to their biological and pharmacological activity.

The unprecedented detection of the intermediate formation of N-hydroxy derivatives during the carbonylation of 2'-nitrochalcones and 2-nitrostyrenes catalysed by palladium

Abstract The carbonylation of 2′-nitrochalcones ( 1 ) in tetrahydrofuran, catalysed by Pd(TMB) 2 (TMBH=2,4,6-trimethylbenzoic acid) at 30 atm of carbon monoxide and 170°C, gave the corresponding quinolones ( 2 ), together with the N -hydroxyquinolones ( 3 ). In some cases the latter become the most abundant products. Similar reactions have been observed in the carbonylation of 2-nitrostyrenes ( 4 ) with the same catalytic system but in the presence of TMPhen (3,4,7,8-tetramethyl-1,10-phenanthroline), which gave the corresponding indoles ( 5 ), together with the N -hydroxyindoles ( 6 ). This is the first case where the formation of N -hydroxy derivatives has been observed during the catalytic carbonylation of organic nitro compounds. The use of Pd/C without any additive as catalyst has also been investigated.

Ultrasound-enhanced one-pot synthesis of 3-(Het)arylmethyl-4-hydroxycoumarins in water

3-(Aryl)methyl-4-hydroxycoumarins were produced in good to excellent yields by reaction between 4-hydroxycoumarin and (hetero)aromatic aldehydes in the presence of Hantzsch 1,4-dihydropyridine (HEH) which works as an hydride donor (i.e., in a sequential Knoevenagel-reductive Michael addition). The sonochemical-assisted procedure (method B) provides an improved and accelerated conversion when compared to conventional silent reactions (method A). Experiments carried out according to method B showed that the reaction could be more efficiently run in the absence of organic solvents, at 30-40°C in open vessel, without the need of an excess HEH and with simplified work-up and separation procedures.

Carbene complexes of cycloplatinated 1H-indole-1-methyl-2-(2′-pyridine). The crystal and molecular structure of σ-{Pt[1H-indole-1-methyl-2-(2′-pyridinyl-C3,N′](DMSO)Cl} and of σ-{Pt[1H-indole-1-methyl-2-(2′-pyridinyl-C3,N′)][C(OCH2CH3)(CH2C6H5)]Cl}

Abstract Reaction of 1-methyl-2-(2′-pyridinyl)-1 H -indole ( 1 ) with PtCl 2 (DMSO) 2 (DMSO=dimethylsulfoxide) gave the cycloplatinated product 2 ; X-ray structure determination of 2 showed a metallation to platinum via the C3 carbon of the indole nucleus, which is chelated to the metal via the pyridine nitrogen atom. Compound 2 reacts with neutral ligands such as CO, Bu t NC, styrene and phenylacetylene, to give compounds 3 – 6 respectively, where DMSO is replaced by the neutral ligands. The phenylacetylene derivative 6 reacts with ethanol to give the carbene complex 7 , whose X-ray structure has been determined. Related carbene complexes with other alcohols and other acetylenic derivatives have also been synthesised.

Diruthenium(II,II) tetrakis(acetate) as a catalyst of choice for intermolecular insertion of stabilized diazocompounds into OH bonds

Abstract In the presence of 3 mol% of [Ru(OAc) 2 ] 2 at 90°C in hexafluorobenzene or alcohols as solvents the highly stabilized diazocoumarin 1 undergoes insertion into the OH bond of alcohols (and phenols) regio- and chemoselectively, affording the corresponding 3-alkoxy-4-hydroxycoumarin in moderate to excellent yields.

Amination of benzylic C–H bonds by aryl azides catalysed by CoII(porphyrin) complexes. A new reaction leading to secondary amines and imines

CoII(porphyrin) complexes catalyse the reaction of aromatic azides, ArN3, with hydrocarbons containing a benzylic group, R1R2R3CH, to give the corresponding amines, R1R2R3C-NHAr. When at least one of the R1–R3 substituents is hydrogen, the catalytic reaction proceeds further to give the imines R1R2CNAr in good yields.

Reductive amination with zinc powder in aqueous media

Summary Zinc powder in aqueous alkaline media was employed to perform reductive amination of aldehydes with primary amines. The corresponding secondary amines were obtained in good yields along with minor amounts of hydrodimerization byproducts. The protocol is a green alternative to the use of complex hydrides in chlorinated or highly flammable solvents.

Tetraalkylammonium N-chloro-p-toluenesulfonamide as aminating agent of olefins

The alkylammonium salt of chloramine-T has been used as aminating agent of olefins in the presence of M(TPP)Cl (M = Fe, Mn; TPP = tetraphenylporphyrin) as catalyst. Main products were the corresponding allylamine, the aziridine, the α-chloro-amine derived by attack of chloride ion on the less substituted carbon of the aziridine, and toluene-p-sulfonamide. The reaction gave reasonable yields of the products with unsubstituted cyclic olefins, while poor results have been obtained with norbornene and 1-hexene.

Rhodium(II) catalysed decomposition of 3-diazo-4-hydroxycoumarin: An easy access to furocoumarin ring system

Several furo[3,2-c]coumarins are produced efficiently and regioselectively by a formal [3+2] cycloaddition of 3-diazo-4-hydroxycoumarin and oxygenated alkenes, presumably via the intermediacy of rhodium carbenoid.