Reaction functional group switching

In addition, the absorption spectra and fluorescence intensity of some porphyrins changed along with the photochromic reaction of the dithienylethene functional group, which was possible for constructing some optical chemical switching systems with emission signal. 

Ramamurthy et al. have examined enantioselective and diastereoselective ODPM rearrangements of cyclohexadienone and naphthalenone derivatives within MY zeolites, where M is an alkali ion [38, 39]. For example, in Scheme 4.27, in NaY in the presence of several chiral inductors such as ephedrine, pseudoephedrine, and camphorquinone-3-oxime, an enantioselective ODPM rearrangement of 65 and 66 took place to afford 68 in 30% ee yield. In the frame of the chiral auxiliary approach, the compound 67 linked to (S)-ephedrine was irradiated within NaY to give 68 in moderate diastereoselective excess (de) (59%). Interestingly, the reaction media of KY, RbY, and CsY reverse the diastereoselectivities. The cation-dependent diastereo-meric switch has been discussed with respect to the N- or O-functional group in 67 [39]. Recently, Arumugan reported that the irradiation of naphthalenones 65 linked chiral auxiliaries (R3 = COO(—)-Ment or (S)-NHCH(Me)Ph) in Li+ or Na + Nafion resulted in chiral products ( 14% de) [40],... 

The Mn mediated radical additions offer an inherently flexible carbon carbon bond construction approach to amine synthesis. Because of the broad functional group compatibility in both the radical precursor and the aldehyde hydrazone acceptor, the roles of these precursors can be switched to result in the construction of either of two C C bonds at the chiral amine (Scheme 2.10) with excellent stereocontrol. The epimeric configuration can be selected by either (a) employing the enantiomeric auxiliary or (b) interchanging the roles of R and in the alkyl halide and aldehyde precursors [47]. By combining these two tactics, the optimal roles of R and with respect to yield and selectivity can be chosen. Such strategic flexibility contributes to the synthetic potential of these radical addition reactions. 

A pinacol-pinacolone rearrangement reaction involving polarity switch of a polar to a nonpolar functional group in a resist polymer has been exploited in... 

Thermodynamic control of reactivity - control of reactivity by an external switching off a stereoelectronic effect The simple comparison of electronic effects in reactant and product is sufficient for reactions that proceed under thermodynamic control. It is common for chemical reactions to proceed from reactants that have relatively weak stereoelectronic stabilization to products where such stabilization is stronger. In such situations, switching off a stereoelectronic effect can be used to reverse position of equilibrium between two common functional groups. As is well-known, amides are more stable than esters due to the greater magnitude of the n, c=o interaction in amides in comparison to the n, Jt c=o interaction... 

Self-doping can be further exploited by utilizing functional groups, where ionization is a result of complexation reactions. For example, boronic acid groups react reversibly with diols and Lewis-base donors to form boronates. As a result, this chemistry can be used to reversibly switch between self-doped and nonself-doped forms of conjugated molecules to impact solubility, reactivity and conductivity. ... 

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