Group 15 Nucleophiles. Nitrogen

Aminocarbenes are formed from NH3, primary or secondary amines (Equation 1.17)  

Pyridines and other heterocyclic nitrogen bases add to Q (Equation 1.18) 

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BMI was also used as a crosslinking agent for poly(iminoethylene). The Michael addition takes place with the nucleophilic nitrogen of the imino group and the double bonds of the electrophilic BMI. The Michael addition of BMI is now adopted as a crosslinking reaction for polymers with amino end groups [2]. 

The relation of the activation by a nitro group to that by an azine-nitrogen in various bicyclic positions provides information in support of that available from studies of azines and forms the basis for certain predictions of azine reactivity. The data tabulated in Section IV, A, 2 also provide a few comparisons of leaving groups, nucleophiles, and deactivating and activating substituents (cf. Sections II, E and III, A, 2). 

Sulfur-stabilized ylides underwent photodriven reaction with chromium alkoxy-carbenes to produce 2-acyl vinyl ethers as E/Z mixtures with the E isomer predominating (Table 22) [ 121-123]. The reaction is thought to proceed by nucleophilic attack of the ylide carbon at the chromium carbene carbon followed by elimination of (CO)5CrSMe2. The same reaction occurred thermally, but at a reduced rate. Sulfilimines underwent a similar addition/elimination process to produce imidates or their hydrolysis products (Table 23) [ 124,125]. Again the reaction also proceeded thermally but much more slowly. Less basic sulfilimines having acyl or sulfonyl groups on nitrogen failed to react. 

Figure 17.18 The Staudinger ligation reaction uses a modified phosphine derivative containing an electrophilic group that acts as a trap for the nucleophilic nitrogen in the intermediate aza-ylide. The resultant shift yields an amide bond derivative between the phosphine-containing molecule and the azide-containing molecule.

Figure 17.23 A traceless Staudinger ligation process involves the formation of an intermediate aza-ylide with subsequent attack of the nucleophilic nitrogen atom on the neighboring electrophilic group. The formation of an amide bond then occurs concomitant with the loss of the phosphine component, thus forming a zero-length crosslink between the two molecules.

Arenecarbonitrile oxides react with alkyl (p-nitrophenyl)carbamates at the nitro group, the nitrogen atom of the latter being the nucleophilic center. Tautomeric N-hydroxybenzimidazole N-oxides 382 and 383 form as the final products (430). 

The anodic oxidation of nitrogen compounds provides an excellent example of how the use of electrochemistry can alter the way in which we view the syntheses of complex organic molecules. Currently, there are two main thrusts to these efforts. First, the oxidation reactions allow for a reversal in the polarity of known functional groups, and therefore molecules with nucleophilic nitrogens can he converted into electrophiles. Second, the oxidation reactions allow for the selective... 

The A -l,2,3,5-thiatriazoline A-oxides (20) are stable at room temperature but are easily hydrolyzed <85TL6155>. Sulfinylamines are known to react with carbonyl compounds and so with R = CHjCOPh, R = Me, an intramolecular trapping of the carbonyl group leading to a 6-membered pyrazine might have been expected. However, even in this case, the 1,2,3,5-thiatriazole S-oxide was formed due to preferential reaction with the highly nucleophilic nitrogen over cycloaddition <86H(24)1193>. 

As was already shown in Scheme 11, benzothiazine ylides have a nucleophilic nitrogen that was protonated with loss of the A-alkyl group even when heated in dimethyl sulfoxide (DMSO). Reacting the ylides 84, 183, and 184 with acid results in the same transformation (Equation 4) <1982J(P1)831>. Compound 114 and the 4-chlorophenyl derivative 185 could also be protonated with perchloric acid but in this case S-dealkylation did not occur and a salt was obtained (Equation 5) <1986LA1648>. 

When a-substituted JV,iV-dimethylacetamidines are used as the bidentate nucleophiles, the reaction proceeds according to Scheme 6. The primary attack occurs at an a position by the nucleophilic nitrogen to yield the zwitterionic adduct 77 (Amax = 506 nm) and is followed by intramolecular ring closure at the y position leading to a bicyclic adduct (78). In contrast, with the N-oxide of 3,5-dinitropyridine the points of attachment of the reagent are both a to the aza group. 

An important pyrrole synthesis, known as the Knorr synthesis, is of the cyclizative condensation type. An a -amino ketone furnishes a nucleophilic nitrogen and an electrophilic carbonyl, while the second component, a /3-keto ester or similar /3-dicarbonyl compound, furnishes an electrophilic carbonyl and a nucleophilic carbon. The initial combination involves enamine formation between the primary amine and the dicarbonyl compound. Subsequent cyclization occurs as a result of the nucleophilic jg-carbon of the enamine adding to the electrophilic carbonyl group of the a-amino ketone (equation 76). Since a-amino... 

On the other hand, it seems less likely that the relative reactivities of n-nucleophiles should be independent of the reactivity of a carbocation. At least when they act as bases, there is little or no evidence that changes in structure of n-nucleophiles lead to changes in intrinsic barrier.301 One might expect therefore that carbocations of different reactivities reacting with a structurally related group of nitrogen or oxygen nucleophiles would show different slopes of plots of log k versus log K. 

Usually, the reactions of carbonyl compounds and derivatives of ammonia are considered to be concluded with the formation of the imino derivative (156), but there is evidence that the C=N double bond may react faster than the C=0 group with nitrogen nucleophiles to form 1,1-diamino derivatives (Scheme 47). 

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