Incompatible functional groups

Mannich bases (2-aminoethyl ketones) are another class of inherently unstable compounds which often undergo facile thermal elimination of the amine to yield a vinyl ketone [30], Chemically related to Mannich bases are 2- or 4-(aminomethyl)- 

Alkenes substituted with an electron-withdrawing (Z) and an electron-donating group (X) will be less reactive than the unsubstituted alkene if the substituents are vicinal (Z-C=C-X push-pull alkenes), but will generally become highly reactive when these two substituents are bound to the same carbon atom. The latter type of alkene (ZXC=CR2 1,1-captodative alkenes) readily dimerize to yield cyclobutanes and can react with 1,3-dienes to yield products of [2 + 2] and/or [2 + 4] cycloaddi- 

The different reactivity of 1,2- and 1,1-acceptor/donor-substituted alkenes is paralleled by the readiness with which these compounds can be prepared. Thus, /3-amino acrylates are often spontaneously formed by mixing amines with /3-keto esters, and these derivatives have been used as protective groups for amines because of their low reactivity. a-Amino acrylates can, similarly, be prepared from a-keto esters [40], but this condensation reaction does not proceed spontaneously and requires chemical or azeotropic removal of water [41—43]. a-Amino acrylates are unstable compounds which must be stored at low temperatures [41] or N-acylated immediately after their generation [43]. 

Ground-state stabilization by hyperconjugation can modify the reactivity of organic compounds significantly, and must be taken into account when estimating the stability of certain types of compound. Di- or polysubstituted methanes can have high ground-state stability if the substituents are simultaneously a-acceptors and jt-donors, as is observed for many heteroatoms. If, on the other hand, the substitu- 

These effects, which have also been called symbiosis, double bond-no bond resonance, clustering, or geminal or anomeric effect [54], can also be explained in terms of the HSAB principle X3C+ will be harder than H3C+ if X is hard. Accordingly, X3C+ will have a higher affinity for the hard X- than H3C+ will have [54]. 

---

Ramberg-Bkcklund reactions are always performed under basic conditions, and sulfones containing incompatible functional groups must obviously be protected. Carbonyl groups, for example, may be... 

Performing multiple reactions simultaneously in a single step offers possibilities for reduced waste and increased safety as well as manipulation of equilibria. This approach was inspired by the action of enzymes, which constitute interesting examples of multifunctional catalysts as they can promote multi-step reactions. In fact, enzymes immobilize mutually incompatible functional groups in a manner that maintains their independent functionality and, as such, are able to carry out multi-step reaction sequences with functionalities that would not be tolerated together in solution. 

Require tests for the presence of functional groups which are necessary for the reaction, on the atoms near the bond made. Reject searches for the presence of incompatible functional groups and interfering side reactions. These tests are coded in a binary form, so that they are performed very rapidly by simple mathematical operations. ... 

Protect functional groups which may be incompatible with a set of reaction conditions... 

The procedures presented here are simple, Inexpensive, and may be used on a large scale. The use of potassium hydroxide In this reaction may, however, prove Incompatible with certain base-sensitive functional groups. 

In an organic synthesis, it sometimes happens that one of the reactants contains a functional group that is incompatible with the reaction conditions. Consider, for exanple, the conversion... 

Many functional groups ate incompatible with otgatiolithiutn reagents. Execution of transmetalations at very low temperatures, however, enables functionalized... 

If attachment of a particular constituent is incompatible with peptide synthesis, or detrimental to self-assembly, an alternative approach would be to add a functional group that selectively binds this molecule. After synthesis and self-assembly of the peptide, the difficult molecule could be introduced to the binding site included on the peptide. 

Despite the moderate to good yields obtained for a range of primary and secondary nitramines, the above methods have not found wide use. Their use in organic synthesis is severely limited by the incompatibility of many functional groups in the presence of strong bases. This is particularly relevant to the synthesis of explosive materials, where nitrate ester and C-nitro functionality are incompatible with strong bases. 

---