Supramolecular approaches to mediate chemical reactivity

• Pablo Ballester,
• Qi-Qiang Wang and
• Carmine Gaeta

Beilstein J. Org. Chem. 2022, 18, 1463–1465, doi:10.3762/bjoc.18.152

• whose geometry, in low-polarity solvents, is controlled by the 1,2,3-alternate conformation of the calix[6]arene skeleton. These catalysts can tune the selectivity of the catalytic cycloisomerization of 1,6-enynes in response to the relative orientation of the coordinated gold(I) atom with respect to

Diametric calix[6]arene-based phosphine gold(I) cavitands

• Gabriele Giovanardi,
• Andrea Secchi,
• Arturo Arduini and
• Gianpiero Cera

Beilstein J. Org. Chem. 2022, 18, 190–196, doi:10.3762/bjoc.18.21

• macrocyclic cavity. Keywords: 1,2,3-alternate conformation; calix[6]arenes; gold(I) catalysis; phosphines; Introduction One of the latest challenges in supramolecular chemistry is the design and development of novel macrocyclic-based entities able to influence the catalytic activities of the metal center [1

• dictate the position of the metal centers, we reasoned on the possibility to design a novel generation of diametric phosphine gold(I) cavitands exploiting a calix[6]arene scaffold characterized by a 1,2,3-alternate conformation. As working hypothesis, this geometry would segregate two catalytically active

• low polarity solvents, is dominated by the 1,2,3-alternate conformation assumed by the DN intermediate, as previously demonstrated in our recent contributions [33][34]. Hence, the most notable features of 1H NMR for A(AuCl)2 are represented by a pattern for the methylene bridging protons in a 1:1:1

Calix[6]arene-based atropoisomeric pseudo[2]rotaxanes

• Carmine Gaeta,
• Carmen Talotta and
• Placido Neri

Beilstein J. Org. Chem. 2018, 14, 2112–2124, doi:10.3762/bjoc.14.186

• the 1,2,3-alternate conformation of 1 is the presence of the broad singlet at 3.71 ppm which correlates in the HSQC spectrum with a carbon resonance at 34.1 ppm [30], related to anti-oriented Ar rings. A close inspection of the 1D and 2D NMR spectrum of 1 in CDCl3 at 233 K clearly evidenced the

• an ArCH2Ar methylene bridge between anti-oriented Ar rings. These data clearly indicate that calixarene-wheel 1 adopts the 1,2,3-alternate conformation in pseudorotaxane 2+11,2,3-alt (Figure 5 and Figure 6). A further inspection of the 1D and 2D (COSY-45 and HSQC) spectra of the 1:1 mixture of 1 and

• standard) [37] for the formation of 2+1cone pseudorotaxane. In conclusion, after the initial formation of the kinetically favored pseudorotaxane 2+11,2,3-alt (Figure 5), the thermodynamic pseudorotaxane 2+1cone prevails (Figure 5 and Figure 6). As demonstrated above, the 1,2,3-alternate conformation of 1