Octaamide hemicarcerands

Abstract

The syntheses, characterization (including a crystal structure determination), and limited constrictive binding properties of two octaamide hemicarcerands are reported, as well as a fourfold rearrangement of an acid-acetal to a phenol-lactone-acetal, the crystal structure of which has been determined. ~We previously reported the synthesis and constrictive binding properties of hydrolytically unstable hemicarcerands 11 and 22 with portals and enforced interiors large enough to admit and expel neutral guests at high temperatures, but which were stable at ambient temperature. We now report the syntheses and characterization of the hydrolytically more stable systems, 3 and 4, derived from 5-10, and the interesting rearrangement of the tetracarboxylic acid related to 8 to give 11.The syntheses of 3 and 4 were accomplished by the reaction sequences 53 + St + 91 -+ 31, and 63 -+ lot 3 4,T?-These new compounds all gave C, H and N (when present) within 0.30% of theory, Mmlz signals of substantial intensity, and lH and 13C NMR spectra consistent with their structures.

Improved Synthesis of Monohalogenated Cavitands and Their Use in the Synthesis of Further Functionalized Cavitands

“…To gain access to monocarboxycavitand 8, we first tried to directly carboxylate cavitand 1 with carbon dioxide in analogy to the work of Cram et al who synthesized tetracarboxylated cavitands. 9 To our surprise all of our approaches to lithiate 1 or monobrominated 2 and then treat the resulting organolithium compound with carefully dried carbon dioxide 10 only resulted in non-functionalized cavitand 1 in both cases. It seems that carbon dioxide is simply not reactive enough to achieve the desired functionalization of the sterically crowded 1 under the conditions employed.…”

Transformation of a [4+6] Salicylbisimine Cage to Chemically Robust Amide Cages

“…However, larger amide cages have been synthesized by multiple bond formations in one step, as well as by the above‐mentioned stepwise approaches. Here, a template effect cannot be exploited and indeed the yields drop substantially, for example, to 7 % for a [2+4] octaamide cage based on resorcinarene tetrakis(acid chlorides) and meta ‐phenylenediamines . For comparison: The structurally related corresponding imine cage is synthesized by DCC in much higher yields of 45 % .…”

Experimental study of hydrodynamics and bubble size distribution of an external loop airlift reactor

“…The external loop airlift reactor (ELALR) has many advantages such as uniform material mixing property, vigorous turbulence, scattered bubbles, large mass transfer area, etc . It is the main piece of equipment for the production of ammonia phosphate.…”