By hydrolysis of imines

Substituted a-amino esters can be prepared by hydrolysis of imines obtained by alkylation of imine (51) with allylic acetates or... 

OH, -N -0.0004 Reductive cleavage of isoxazole followed by hydrolysis of imine to carbonyl... 

The transaldolase functions primarily to make a useful glycolytic substrate from the sedoheptulose-7-phosphate produced by the first transketolase reaction. This reaction (Figure 23.35) is quite similar to the aldolase reaction of glycolysis, involving formation of a Schiff base intermediate between the sedohep-tulose-7-phosphate and an active-site lysine residue (Figure 23.36). Elimination of the erythrose-4-phosphate product leaves an enamine of dihydroxyacetone, which remains stable at the active site (without imine hydrolysis) until the other substrate comes into position. Attack of the enamine carbanion at the carbonyl carbon of glyceraldehyde-3-phosphate is followed by hydrolysis of the Schiff base (imine) to yield the product fructose-6-phosphate. 

A somewhat more complex side chain is incorporated by alkylation of the carbanion of the substituted cyanoacetate, 148, with 2-chloroethylmethyl sulfide. Condensation of the resulting cyanoester (149) with thiourea followed by hydrolysis of the resulting imine (150) affords methitural (151)... 

With most reducing agents, reduction of carboxylic acids generally gives the primary alcohol (19-34) and the isolation of aldehydes is not feasible. However, simple straight-chain carboxylic acids have been reduced to aldehydesby treatment with Li in MeNH2 or NH3 followed by hydrolysis of the resulting imine, ... 

Whereas pyrroles normally undergo substitution at the C-2 position, 1-arylsulfonylpyrroles display a tunable reactivity in Friedel-Crafts acylations, wherein substitution occurs at C-3 in the presence of "hard acids" such as aluminum chloride but mainly at C-2 when catalyzed by weaker acids <81TL4899,81TL4901>. An alternative route to 3-aroylpyrroles 38 has been introduced via irradiation of 1-acetyl- or 1-phenylsulfonylpyrrole (36) with arenethiocarboxamides <96H(43)463>. The proposed mechanism involves formation and scission of a thietane intermediate 37, followed by hydrolysis of the resultant imine. 

The synthesis pathway of quinolizidine alkaloids is based on lysine conversion by enzymatic activity to cadaverine in exactly the same way as in the case of piperidine alkaloids. Certainly, in the relatively rich literature which attempts to explain quinolizidine alkaloid synthesis °, there are different experimental variants of this conversion. According to new experimental data, the conversion is achieved by coenzyme PLP (pyridoxal phosphate) activity, when the lysine is CO2 reduced. From cadeverine, via the activity of the diamine oxidase, Schiff base formation and four minor reactions (Aldol-type reaction, hydrolysis of imine to aldehyde/amine, oxidative reaction and again Schiff base formation), the pathway is divided into two directions. The subway synthesizes (—)-lupinine by two reductive steps, and the main synthesis stream goes via the Schiff base formation and coupling to the compound substrate, from which again the synthetic pathway divides to form (+)-lupanine synthesis and (—)-sparteine synthesis. From (—)-sparteine, the route by conversion to (+)-cytisine synthesis is open (Figure 51). Cytisine is an alkaloid with the pyridone nucleus. 

The initial success with early transition metals, such as zirconium and titanium, reported by the Buchwald group, included an indirect cycloaddition between an enyne and isocyanides. The first protocol that used [Gp2Ti(PMc3)2] or Ni(GOD) together with triphenylphosphine failed to cyclize the enynes under the pressure of GO, but provided the cyclic imines with trialkylsilyl isocyanides, and bicyclic enones were obtained by hydrolysis of the resultant imine products (Equation (9)). ... 

Photocyclization of a,/3-unsaturated amides (152) also gives /3-lactams. This proceeds by cleavage of the intermediate biradical (153) to give ketene and imine which recombine. A small amount of amide (154) results from reaction of the ketene with amine that is produced by hydrolysis of the imine. This type of photodealkylation detracts from the generality of the process (79JCS(P1)263, 77T485). 

Formation of C—N bonds is frequently achieved by condensation reactions between amines and aldehydes or ketones. A typical nucleophilic addition is followed by elimination of water to give an imine or Schiff base [Figure 2.12(a)], Of almost equal importance is the reversal of this process, i.e. the hydrolysis of imines to amines and alde-hydes/ketones [Figure 2.12(b)], The imine so produced, or more likely its protonated form the... 

One of the paradoxes of metal-imine chemistry is the observation that in many cases the imine is stabilised with respect to nucleophilic attack by water upon co-ordination, but is still prone to attack by amines. We saw in Chapter 4 how the hydrolysis of imines may be either promoted or inhibited by co-ordination to a metal, and we also saw a number of examples involving nucleophilic attack on an imine by a variety of other nucleophiles. A special case of such a nucleophilic attack involves another amine. The consequence is a transimination reaction, as indicated in Fig. 5-53. Presumably, intermediates of type 5.26 are involved. The procedure is of some synthetic use for the preparation of imine complexes (Fig. 5-54). 

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