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The site-selective α-allylic alkylation of enones with alcohols via gold-triggered formation of nucleophilic allenoates by means of [3,3]-sigmatropic rearrangements of propargylic carboxylates is reported. A range of α-alkylated enones is obtained in high yields in the presence of the gold complex [JohnPhosAu(ACN)]SbF6 (2 mol%) as the promoting agent. Examples of allylation/Friedel–Crafts alkylation sequences are also provided, delivering densely functionalized dihydroindenes and dihydrobenzo[7]annulenes in a one-pot procedure in moderate yields. The role of the Bronsted acidity (i.e., pivalic acid) delivered during the reaction course in assisting the formation of carbocationic intermediates is documented.

The gold-catalyzed synthesis of methylidene 2,3-cyclobutane-indoles is documented through a combined experimental/computational investigation. Besides optimizing the racemic synthesis of the tricyclic indole compounds, the enantioselective variant is presented to its full extent. In particular, the scope of the reaction encompasses both aryloxyallenes and allenamides as electrophilic partners providing high yields and excellent stereochemical controls in the desired cycloadducts. The computational (DFT) investigation has fully elucidated the reaction mechanism providing clear evidence for a two-step reaction. Two parallel reaction pathways explain the regioisomeric products obtained under kinetic and thermodynamic conditions. In both cases, the dearomative CC bond-forming event turned out to be the rate-determining step.

The Boulton–Katritzky reaction represents one of the most popular and efficient strategies used to realize azole-into-azole conversions. For example, under different experimental conditions, it allows the rearrangement of Z-arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazoles (1) into 2-aryl-4-benzoylamino-5-phenyl-2H-1,2,3-triazoles (2) in very high yields. Moreover, we have recently realized this conversion also by UV-photostimulation. Now we have enlarged the scope of the reaction irradiating with visible or UV light an acetonitrile solution of some Z-arylhydrazones (1a–e) in the presence of catalytic amounts of Ru(bpy)2Cl2. We have observed the unexpected formation of the 1-aryl-5-benzoylamino-3-phenyl-1,2,4-triazoles (3a–e) eventually together with the expected 2a–d in high yields.

A new Michael-Michael cascade reaction between 2-(2-oxoindolin-3-ylidene)acetic esters 1 and nitroenoates 2, catalyzed by bifunctional thioureas, is investigated. The combination of the two Michael reactions results in a novel and facile [4+2] or [3+2] spiroannulation process, which is characterized by the following features: 1) two carbon-carbon bonds and four stereocenters, including a quaternary spiro carbon, are formed under mild conditions; 2) an unprecedented and stereochemically defined substitution pattern on the spirocarbocyclic unit is obtained; 3) the double-bond configuration of the donor-acceptor nitroenoate 2 determines the absolute configuration of the spiro center, whereas the remaining stereocenters are formed under control of the catalyst. The effect on the final stereochemical outcome of structural variations of each starting material, catalyst, and experimental conditions is analyzed in detail. In particular, the use of specifically designed chiral nitroenoates enables diverse polyfunctional spirocyclohexane derivatives containing six consecutive stereogenic centers to be constructed. To our knowledge, this is the first asymmetric organocatalytic strategy enabling both five- and six-membered β-nitro spirocarbocyclic oxindoles.

The [2+2]-cycloaddition between indoles and allenamide gives access to methylenecyclobutanes representing competent buildings block in organic synthesis which are especially attractive in future synthesis of indole based alkaloids.

The reaction can be applied in a one-pot dearomatization/hydrogen-transfer cascade reaction giving trans-indolines (XII) in good yields and with high stereoselectivities.

A systematic investigation of the gold-catalyzed dearomatization of indoles with allenyl substituted tertiary amines is reported.

The highly diastereoselective anti-dioxylation of (1R,2R)-1,2-bis[(1S)-phenylethylamino]cyclohexene was accomplished through epoxidation of the double bond with m-chloroperbenzoic acid (mCPBA) in the presence of a sulfonic or trihaloacetic acid and ring opening of the epoxide in situ in the presence of sulfonate or carboxylate anions. The two procedures, after basic quenching and reductive removal of the N-substituents, provide stereoselective access to 2-exo-5-endo-5-amino-7-azabicyclo[2.2.1]heptan-2-ol and 4,5-diaminocyclohexane-1,2-diol, respectively. The different outcomes are explained by differing chair conformations of the protonated diamine-epoxide intermediates, which undergo ring opening through a preferred anti-diaxial mechanism.

An uncatalyzed aldol-type reaction of aromatic N-trimethylsilyl ketene imines with O-protected α-trialkylsilyloxy or α-benzyloxy aldehydes is reported. It is shown that N-trimethylsilyl ketene imines (SKIs) are essential for the success of this aldol-type reaction, and that almost complete control of stereochemistry in the formation of the stereocentre vicinal to the stereogenic centre present in the starting aldehyde is seen when these compounds are used. A very high syn stereoselectivity was observed at room temperature, and a reversal of stereoselectivity to favour the formation of the anti product may be achieved at low temperature. Preliminary theoretical calculations support the hypothesis that the aldol-type reaction is facilitated by the formation of a cyclic transition state, with concomitant silatropic migration from the ketene imine-nitrogen to the aldehyde oxygen. The catalyst-free aldol reaction has been applied to aromatic N-trimethylsilyl ketene imines bearing two different aromatic groups. In these reactions, the diastereoselectivity for the stereocentre arising from aldehyde sp2 carbon remained extremely high, but the stereoselectivity for the formation of the new quaternary stereocentre was unsatisfactory.

Target compound (V) is alternatively prepared via Stille coupling of bromo thiophene (I) with 5,5′-bis(tributylstannyl)-2,2′-bithiophene.

An unprecedented atom/step economic synthesis of the title compounds (II) and (IV) is presented with a high level of chemo-, regio-, and diastereoselectivity.

The diastereomeric intramolecular nucleophilic alkoxylation of enantioenriched allylic alcohols, e.g. (I), (IV) or (V), is efficiently catalyzed by a Au(I)—Ag(I)—dppf complex to give vinylmorpholines in high yields and excellent diastereoselectivities (up to < 96% d.e.).

Silyl-substituted triosmium clusters of general formula [Os3H(CO)11(SiR3)](1) or [Os3H(CO)10(MeCN)(SiR3)](2)[R3=(OMe)3, (OEt)3, Et3, or HPh2] can be synthesized from the reaction of the silane derivatives SiHR3 with the activated clusters [Os3(CO)11(MeCN)] and [Os3(CO)10(MeCN)2], respectively. The complex [Os3H(CO)11{Si(OEt)3}] is easily deprotonated by triethylamine affording the highly reactive anion [Os3(CO)11{Si(OEt)3}]– which has been isolated as the salt [NHEt3][Os3(CO)11{Si(OEt)}3](3b). A study of the reactivity of (3b) towards Group 1B and 2B metal ions has been undertaken and the reaction products characterized on the basis of their spectroscopic properties.

Enantiopure 1-(2-pyridyl)alkyl aziridines were designed as bidentate ligands for asymmetric catalysis. Their synthesis involved the addition of organometallic reagents to the imine prepared from 2-pyridinealdehyde and an enantiopure β-aminoalcohol, followed by cyclisation of the β-aminoalcohol moiety to the aziridine ring. Two such ligands (N–N)* were prepared from ( S )-valinol and converted to the complexes (η 3 -allyl)(N–N)*Pd + SbF 6 − , one of which was characterised by X-ray crystallography. Modest enantioselectivities were achieved in a representative Pd-catalysed allylic substitution reaction.

A new class of remarkably stable B-BOXate complexes has been synthesised, isolated and employed as chiral catalysts for asymmetric reduction of variously substituted prochiral ketones.

A variety of chiral bis-pyrroles have been made readily accessible via acid-catalyzed condensation of chiral ketones with pyrrole. Three representative chiral ketones 2 - 4 taken from the chiral pool were transformed into the corresponding bis-pyrrole derivatives in a straightforward acid-catalyzed condensation. Chiral β-hydroxy ketone derivatives, prepared through proline-catalyzed aldol condensation of acetone and an aldehyde, are readily transformed into the corresponding dipyrrolylmethane by the acid-catalyzed condensation carried out in the same conditions. The crystal structure of the chiral dipyrrolylmethane 2 derived from the (-)-menthone was determined.

A fast and highly regio- and stereoselective transformation of non-conventional β-lactam-containing epoxides into the corresponding cyclic 1,3-dioxolanes and oxazolines is herein reported, using microwave irradiation as an efficient source of energy, in the presence of stoichiometric or catalytic amounts of Lewis acids, without an additional solvent. These cyclic compounds are the protected forms of diols and amino alcohols.

The first total synthesis of (R)-convolutamydine A has been achieved by the organocatalytic addition of acetone to 4,6-dibromoisatin. The absolute configuration was determined by single crystal X-ray diffraction. DFT studies were used to model the transition states for the aldol reaction and equilibrium geometries of the post-aldol reaction intermediates. The DFT study revealed that the aldol bond forming reaction was considerably endothermic.

The reaction between 4-nitroalkoxybenzenes 7 and PCl 3 /AlCl 3 , when carried out in appropriate molar ratio, gives a prevalent formation of diazenes 8 and 2,7-dialkoxyphenazines 9 with their new chlorinated derivatives 10 – 13 . These compounds are obtained, in satisfactory yield, in a one-pot procedure, in mild conditions, from commercially available and safe starting materials. In this reaction both the reagents PCl 3 and AlCl 3 play a fundamental role in obtaining the products, and this method might be applicable to other 4-alkoxynitrobenzenes.

The functionalised cluster Os 3 (CO) 10 (CH 3 CN) 2 reacts at room temperature with trimethylsilylacetylene to afford the orange derivative Os 3 (CO) 10 (Me 3 SiC 2 H) which undergoes decarbonylation and hydrogen migration to give the cluster HOs 3 (CO) 9 (CCSiMe 3 ), which has been fully characterised by an X-ray diffraction study.

The reaction between [(OC)2(cp)FeC(S)SFe(cp)(CO)2](cp =η5–C5H5) and [Co2(CO)8] produces the novel mixed-metal cluster [Co3Fe(cp)(CO)9(CS)] which contains a thiocarbonyl group, and the two known derivatives [Co4(CO)10S2] and [CoFe(cp)(CO)6]. This product distribution, which accounts for the fragmentation and desulphurization of the starting dithioester complex, may be seen as occurring via an unstable dithiocarbene intermediate. The structure of [Co3Fe(cp)(CO)9(CS)] has been determined by X-ray crystallography. The complex crystallizes in the orthorhombic space group Pbca(no. 61) with cell constants a= 16.196(7), b= 12.325(3), c= 18.971(6)A, and Z= 8. The structure has been solved from 1 292 reflections collected by counter methods, and refined by least-squares calculations to R= 0.044 (R′= 0.040). The molecule contains a triangle of Co atoms carrying an external Fe(cp)(CO)2 fragment. The CS group, which lies parallel to the Co3 triangle, contributes six electrons to the cluster orbitals. The carbon atom of this ligand bridges all metal atoms, while the sulphur atom is bonded only to two Co atoms. The bonding mode of the CS ligand is discussed in terms of σ and π interactions.