Chiral selection: achiral guest

As discussed in this chapter, the fundamental host-guest chemistry of 1 has been elaborated to include both stoichiometric and catalytic reactions. The constrained interior and chirality of 1 allows for both size- and stereo-selectivity [31-35]. Additionally, 1 itself has been used as a catalyst for the sigmatropic rearrangement of enammonium cations [36,37] and the hydrolysis of acid-labile orthoformates and acetals [38,39]. Our approach to using 1 to mediate chemical reactivity has been twofold First, the chiral environment of 1 is explored as a source of asymmetry for encapsulated achiral catalysts. Second, the assembly itself is used to catalyze reactions that either require preorganization of the substrate or contain high energy intermediates or transition states that can be stabilized in 1. 

Although a number of impressive chiral, supramolecular architectures were not discussed in this chapter either due to their instability in solution or their inability to encapsulate guest molecules, they should not go unmentioned and are referenced to follow up for the interested reader. Some selected examples are (i) Saalfrank and coworkers octadecametallic square box composed of 52 achiral components with molecular D2 symmetry [160] (ii) Ward and coworkers truncated, cationic tetrahedral cage [Co Lis]244 [161] that encapsulates four tetrafluoroborate counter-ions in the solid state (iii) James... 

B. Gas-Phase Equilibria Mix reference host with enantiopure guest generate complex ions in ESI source mass-select complex in FTICR cell evaporate chiral host and achiral reference host into the analyzer cell at known pressures let the original complex react with both until equilibrium is reached (no signal intensity changes are observed after some time) repeat experiment with other enantiomer of chiral host -> evaluate two ratios of signal intensities of complex ions with chiral and reference host compare intensity ratios. Advantage True gas-phase experiment. 

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