Nitrogen-triggered

Scheme 3.4. A nitrogen-triggered mechanism for the isomerization of allylamine with cationic Rh(I)-BI-NAP complexes.

Mechanistic studies of the isomerization of a prochiral allylamine with a Rh-diphosphine complex gave some evidence for a nitrogen-triggered mechanism in which the allylamine chelates to the metal center. The suggested mechanism, which was elaborated on the basis of a chiral Rh-BINAP catalyst, is depicted in Scheme 4 [8]. 

Keywords Allyl alcohol, Allylamine, Aza-allyl, Azomethine, BINAP, BIPHEMP, Citronellal, Cobalt, DIOP, Enol, Enamine, Imine, Isomerization, Kinetic resolution. Nitrogen-triggered, Rhodium, Ruthenium... 

The square planar complex 73 undergoes P-elimination via liberation of L to form a transient equilibrium of the iminium-rhodium hydride o-complex 74a and the Jt-complex 74b, Eq. 16. These complexes 74a and 74b represent a unique nitrogen-triggered mechanism that is different from either the hydride addition-elimination pathway or the 7i-allyl mechanism resulting in the intramolecular 1,3-hydrogen shift. 

The final mechanistic pathway (c), the so-called nitrogen-triggered mechanism, is responsible for the enantioselective route to (—)-menthol. It comprises, first, co-ordination to the electronegative N-heteroatom followed by abstraction of the acidic a-proton and formation of the three-membered metaUacycle. This intermediate... 

Histamine, whose release in the body triggers nasal secretions and constricted airways, has three nitrogen atoms. List them in order of increasing basicity, and explain your ordering. 

FIGURE 4.18 The rapid decomposition of sodium azide, NaN3, results in the formation of a large volume of nitrogen gas. The reaction is triggered electrically in this air bag. 

These reactions involve addition of the diazo ester to an adduct of the carbonyl compound and the Lewis acid. Elimination of nitrogen then triggers migration. Triethyloxonium tetrafluoroborate also effects ring expansion of cyclic ketones by ethyl diazoacetate.83... 

A rather complex microwave-assisted ring-opening of chiral difluorinated epoxy-cyclooctenones has been studied by Percy and coworkers (Scheme 6.131) [265]. The epoxide resisted conventional hydrolysis, but reacted smoothly in basic aqueous media (ammonia or N-methylimidazole) under microwave irradiation at 100 °C for 10 min to afford unique hemiacetals and hemiaminals in good yields. Other nitrogen nucleophiles, such as sodium azide or imidazole, failed to trigger the reaction. The reaction with sodium hydroxide led to much poorer conversion of the starting material. 

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