Anna Roglans

[2+2+2] cycloaddition reactions of macrocyclic systems catalyzed by transition metals. A review.

Polyalkyne and enediyne azamacrocycles are prepared from arenesulfonamides and various alkyne and alkene derivatives either under basic or neutral conditions. The new family of macrocyclic substrates is tested in the [2+2+2] cycloaddition reaction. Several catalysts are used for the cycloisomerization reaction, and their enantioinduction is evaluated as appropriate. The effect of the structural features of the macrocycles, namely the ring size, substituents in precise positions and the number and type of unsaturations, on the [2+2+2] cycloaddition reaction has also been studied.

Dendritic phosphoramidite ligands for Rh-catalyzed [2+2+2] cycloaddition reactions: Unprecedented enhancement of enantiodiscrimination

Phosphorus dendrimers containing terminal phosphoramidite ligands have been found to be highly effective and recoverable catalysts for the rhodium(I) catalyzed [2+2+2] cycloaddition reactions. A strong positive dendritic effect is observed both in the activity and enantiodiscrimination leading to axially chiral biaryl compounds.

Rhodium(I)‐Catalysed Intramolecular [2+2+2] Cyclotrimerisations of 15‐, 20‐ and 25‐Membered Azamacrocycles: Experimental and Theoretical Mechanistic Studies

A new series of 20- and 25-membered polyacetylenic azamacrocycles have been satisfactorily prepared and completely characterised by spectroscopic methods. Various [2+2+2] cyclotrimerisation processes catalysed by the Wilkinsons catalyst, [RhCl(PPh(3))(3)], were tested in the above-mentioned macrocycles. The 25-membered azamacrocycle (like the previously synthesised 15-membered azamacrocyle) led to the expected cyclotrimerised compound in contrast to the 20-membered macrocycle, which is characterised by its lack of reactivity. The difference in reactivity of the 15-, 20- and 25-membered macrocycles has been rationalised through density functional theory calculations.

P‐Stereogenic Secondary Iminophosphorane Ligands and Their Rhodium(I) Complexes: Taking Advantage of NH/PH Tautomerism

Have a good SIP: P-stereogenic secondary iminophosphorane (SIP) ligands with a sulfonyl group attached to nitrogen have been prepared. In the presence of rhodium, the tautomeric equilibrium is shifted from the favored PH tautomer towards the P(III) tautomer, thereby allowing coordination of the SIP ligand through the P and O atoms. The resulting Rh complexes are effective in the [2+2+2] cycloaddition of enediynes with terminal alkynes.

Palladium(0)-catalyzed allylation of highly acidic and non-nucleophilic arenesulfonamides, sulfamide, and cyanamide. I.

Abstract Arenesulfonamides, sulfamide, and cyanamide are efficiently allylated using allylic carbonates under Pd(0)-catalysis. N -Arenesulfonyl-2,5-dihydropyrroles are obtained by ruthenium-mediated ring closing metathesis of the corresponding N -diallylated compounds. A stereochemical study of the reactions of ethyl cis -(5-methyl-2-cyclohexenyl) carbonate with 2,4,6-triisopropylphenylsulfonamide was performed, clean overall retention of configuration being found with bidentate phosphines.

Allenes, versatile unsaturated motifs in transition-metal-catalysed [2+2+2] cycloaddition reactions

We gratefully acknowledge the financial support of our own research in this area by the Spanish Ministry of Education and Science (MINECO) (Project CTQ2014-54306-P and a RyC contract to A. L.) and the DIUE of the Generalitat de Catalunya (Project 2014-SGR-931)

PALLADIUM(0)-CATALYZED ALLYLATION OF HIGHLY ACIDIC AND NON-NUCLEOPHILIC ARENESULFONAMIDES, SULFAMIDE, AND CYANAMIDE. II. FORMATION OF MEDIUM AND LARGE HETEROCYCLES

Abstract Arenesulfonamides 10, cyanamide 29, and sulfamide 32 react with allylic bis-carbonates 8 ( Z and E ) and 9 under Pd(0)-catalysis to afford medium and large unsaturated heterocycles instead of three and/or five-membered ring compounds. Stable 15-membered palladium-containing rings were also isolated from arenesulfonamides and 8, with three trans olefinic systems coordinated to the metal. NMR and MALDI-TOF MS experiments were used for structure elucidations. Suitable hydrogenation conditions to give the saturated macrocycles have been found.

Direct Detection of Key Intermediates in Rhodium(I)‐Catalyzed [2+2+2] Cycloadditions of Alkynes by ESI‐MS

The mechanism of the Rh-catalysed [2+2+2] cycloaddition reaction of diynes with monoynes has been examined using ESI-MS and ESI-CID-MS analysis. The catalytic system used consisted of the combination of a cationic rhodium(I) complex with bisphosphine ligands, which generates highly active complexes that can be detected by ESI(+) experiments. ESI-MS on-line monitoring has allowed the detection for the first time of all of the intermediates in the catalytic cycle, supporting the mechanistic proposal based mainly on theoretical calculations. For all ESI-MS experiments, the structural assignments of ions are supported by tandem mass spectrometry analyses. Computer model studies based on density functional theory (DFT) support the structural proposal made for the monoyne insertion intermediate. The collective studies provide new insight into the reactivity of cationic rhodacyclopentadienes, which should facilitate the design of related rhodium-catalysed C-C couplings.

Ethyl N-(diphenylmethylene)glycinate as anionic glycine equivalent. Monoalkylation, dialkylation and Michael additions under solid-liquid phase-transfer catalysis

Abstract Ethyl N -(diphenylmethylene)glycinate, 1 , undergoes monoalkylations, dialkylations and Michael additions to ethylenic and acetylenic acceptors under appropriate solid-liquid phase transfer catalysis conditions. Further transformations of the α-disubstituted ketimines lead to α-alkylated aspartic and glutamic acid derivatives 10 , 15 , 19 and 26 , to bicyclic amino acids or derivatives featuring pyrazolone and isoxazolone moieties 30 and 33 , and to α-substituted ( E )-3,4-dehydroglutamic acids.

Dehydrogenative [2 + 2 + 2] Cycloaddition of Cyano-yne-allene Substrates: Convenient Access to 2,6-Naphthyridine Scaffolds

A rhodium-catalyzed [2 + 2 + 2] cycloaddition of cyano-yne-allene scaffolds followed by a dehydrogenative process enabling the direct synthesis of unsaturated pyridine-containing compounds that can be conveniently converted to 2,6-naphthyridine derivatives is reported.