2-Methylpropanal , imine

The reaction of the imines, formed from 2-methylpropanal and (S )-a-methylbenzylamine with tert-butyl isocyanidc and benzoic acid under widely varied conditions, delivers the valine derivatives with only moderate diastcrcoselectivity (ratio of diastereomers less than 4 l)67. 

The reaction of CH )NH2 with 2-methylpropanal can give three possible products two isomeric imines and an enamine. Since the products form reversibly, the reaction is thermodynamically controlled. Use SpartanView to obtain the energies of imine A, iminc B, and the enamine, and predict which is likely to be formed. What factors are responsible for the energy differences between the possible products ... 

The value of K has been measured for several amines with 2-methylpropanal. The effect of the structure of the alkyl group is quite small, although the trifluoroethyl group significantly reduces imine stability. 

Equilibrium Constants for Imines Formation with 2-Methylpropanal... 

The pH-rate profile for the hydrolysis of the A-methylimine of 2-methylpropanal is shown in Figure 7.6. The curve is similar to that for aromatic ketones with EWG substituents. The rate increases in the pH range 0. 5, where decomposition of the zwitterionic intermediate is rate controlling. In the pH range 4.5-8, the rate decreases and then levels off This corresponds to the transformation of the protonated imine to the less reactive neutral form. Above pH 8, the rate is again constant, as the increase in [ OH] is compensated by the decrease in the amount of protonated imine. 

The isolation of the non-cyclic amino(aryl)carbenes and amino(alk-yl)carbenes demonstrated that singlet carbene centres can be sufficiently stabilized by only one a-nitrogen atom. In 2005, Bertrand and co-workers succeeded in preparing the first cyclic alkyl(amino)carbenes (CAACs Scheme 1.15). The precursor for CAAC 108 was obtained from an imine by deprotonation with LDA (LDA = lithium diisopropylamide) and subsequent reaction with 1,2-epoxy-2-methylpropane to give 106, which was converted into cyclic aldiminium salt 107 by reaction with trifluoromethanesulfonic acid... 

The directing effect can also be mediated by imino groups attached to arenes. Thus, the reaction of diaryIzinc reagents with 1-phenylalkane-l-imines in the presence of catalytic amounts of tris(acetylacetonato)iron, 4,4 -di-tert-butylbipyridine (dtbpy), and two equivalents of 1,2-dichloro-2-methylpropane leads to the introduction of an orthoaryl group via C-H activation (Scheme 4-248). 

In analogy to aromatic C-H bonds, alkenyl C-H bonds can also be activated by iron(III) salts in coupling reactions with magnesium or zinc organyls (Scheme 4-250). The reaction requires a pyridine or an imine moiety in proximity to the double bond that supports the C-H bond activation step by chelation of the intermediate iron complex. Tris(acetylacetonato)iron is employed in catalytic amounts and l-bromo-2-chIoroethane or l,2-dichloro-2-methylpropane functions as oxidant. In addition, in most cases a diamine base is added. The reaction results in the stereospecific substitution of the olefinic C-H bond syn to the coordinating group. ... 

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