Cavitands as Reaction Vessels and Blocking Groups for Selective Reactions in Water

• Published in: Angewandte Chemie International Edition Vol. 55; no. 29; pp. 8290 - 8293
• Main Authors: Masseroni, Daniele, Mosca, Simone, Mower, Matthew P., Blackmond, Donna G., Rebek Jr, Julius
• Format: Journal Article
• Language: English
• Published: Germany Blackwell Publishing Ltd 11-07-2016; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Aliphatic compounds; cavitands; Chains; Chemical industry; Chemical reactions; Conformation; Deep water; diazides; Exposure; Organic solvents; Petrochemicals; Phosphine; selectivity; Solvents; Staudinger reduction; Substrates; supramolecular chemistry; Vessels; selectivity; cavitands; Staudinger reduction; diazides; supramolecular chemistry
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201602355

The majority of reactions currently performed in the chemical industry take place in organic solvents, compounds that are generally derived from petrochemicals. To promote chemical processes in water, we examined the use of synthetic, deep water‐soluble cavitands in the Staudinger reduction of long‐chain aliphatic diazides (C8, C10, and C12). The diazide substrates are taken up by the cavitand in D2O in folded, dynamic conformations. The reduction of one azide group to an amine gives a complex in which the substrate is fixed in an unsymmetrical conformation, with the amine terminal exposed and the azide terminal deep and inaccessible within the cavitand. Accordingly, the reduction of the second azide group is inhibited, even with excess phosphine, and good yields of the monofunctionalized products are obtained. In contrast, the reduction of the free diazides in bulk solution yields diamine products.
Reaction shutdown: A deep, water‐soluble cavitand allows the selective monoreduction of diazides to monoamines. The unusual reaction pathway can be explained by different folding conformations of the starting materials and products inside the container.