Elucidating the Importance of Hydrochloric Acid as a Cocatalyst for Resorcinarene‐Capsule‐Catalyzed Reactions

Abstract

This survey of resorcinarene-capsule-catalyzed reactions demonstrates that HCl functions as ac rucial cocatalyst by increasing the capsule's inherentB rønsteda cidity to enableo raccelerate cationic reactions. The presence of HCla ppears to be withoutconsequences for other reactions.[a] J.

Four-Step Access to the Sesquiterpene Natural Product Presilphiperfolan-1β-ol and Unnatural Derivatives via Supramolecular Catalysis

“…Synthesis of resorcinarene 1: Synthesis of resorcinarene 1 was carried out as previously described. 6 Synthesis of cyclization substrates 15 and 16: (−)-Caryophyllene oxide (6.00 g, 27.2 mmol) was dissolved in DCM (150 mL) in a two-neck flask. The solution was cooled to −78 °C and ozone was bubbled through until a blue color persisted; the mixture was then purged with oxygen until disappearance of the blue color.…”

“…3(14) 21.3 3C4 -3895.1 9-4929(2) -2801.0(16) 23.8 4C6 -3494.5 10-5169(2) -3448. 1(16) 24.6 3C8 -4308.0(9) -5276(2) -1381.8 (15) 21.4 3C9 -3590.5 9-4810(2) 4.6(16) 24.1 4C12 -3280.9 9-7451(2) -1092.1 (15) 23.8 3C13 -4598.9 10-3457(2) -2064.6(17) 25.9 4C16 -4700.4 10-7645(2) -3113.8 1727.7 4C17 -3877.4 10-3187 3343.0(17) 31.1 4C19 -4195.3 10 72.2(6) 27.2 70.1 6N7 40.7 (8) 27.0(8) 37.4 91.3 (6) 30.6(8) 1.8 7C10 20.9 (7) 28.9 (8) 19.6(7) 0.5 711.1(6) 1.6(7) C1 21.8 (7) 23.0(8) 20.6(7) -0.2(6) 13.0(6) -0.6(6) C4 22.6(7) 27.2 (9) 22.7(8) 0.8 (6) 13.7(7) -1.3 (7) C6 27.4 (8) 26. 4(8) 25.0(8) 2.2 (7) 18.0(7) -0.7 7C8 18.7 725.5 (8) 22.4 70.1 713.2(6) -0.4 6C9 20.5 728.8 (9) 24.0(8) -6.0(6) 13.3 7-3.0(6) 3 was selected and mounted on a mylar loop in perfluoroether oil on an Bruker APEX-II CCD diffractometer.…”

“…This supramolecular container is able to catalyse the THT cyclization, likely via the stabilization of cationic transition states within its cavity. 6 We also demonstrated that the limited selectivity encountered in the capsule-catalysed cyclizations of linear sesquiterpene precursors could be overcome through the use of a conformationally restricted substrate, in this way achieving the selective preparation of the natural product isolongifolene. 7 However, isolongifolene is a commercially available compound, and it is not known to possess any biological activity.…”

The Hexameric Resorcinarene Capsule at Work: Supramolecular Catalysis in Confined Spaces

“…In conclusion, these results show that the reaction take places inside the cavity of CR 6 and in the presence of HCl as a cocatalyst. In fact, as shown in a recent report, the inherent acidity of CR 6 was not sufficient for the catalysis of the hydrolysis of acetals inside the capsule (Scheme ). No hydrolysis was observed, if the reaction in Scheme was performed in the absence of the HCl cocatalyst.…”

Sesquiterpene Cyclizations inside the Hexameric Resorcinarene Capsule: Total Synthesis of δ‐Selinene and Mechanistic Studies

“…We found that an acid cocatalyst was required to activate the terpene substrate . In several other cases, the intrinsic acidity of the capsule was sufficient to initiate the reaction . In the initial report, a selective cyclization reaction was achieved using the monoterpene geranyl acetate as the substrate.…”