Directing groups amine

In addition to the hydroxy directing group, amines and amides also showed excellent 1,3-asymmetric induction. In conjunction... 

Allyl groups attached directly to amine or amide nitrogen can be removed by isomerization and hydrolysis.228 These reactions are analogous to those used to cleave allylic ethers (see p. 266). Catalysts that have been found to be effective include Wilkinson s catalyst,229 other rhodium catalysts,230 and iron pentacarbonyl.45 Treatment of /V-allyl amines with Pd(PPh3)4 and (V,(V -dimethylbarbi Lurie acid also cleaves the allyl group.231... 

AMCA-NHS, succinimidyl-7-amino-4-methylcoumarin-3-acetic acid, is an amine-reactive derivative of AMCA containing an NHS ester on its carboxylate group (Thermo Fisher). The result is reactivity directed toward amine-containing molecules, forming amide linkages with the AMCA fluorophore (Figure 9.23). Proteins labeled with AMCA show little-to-no effect on the isoelectric point of the molecule. 

A number of BODIPY derivatives that contain reactive groups able to couple with amine-containing molecules are commonly available. The derivatives either contain a carboxy-late group, which can be reacted with an amine in the presence of a carbodiimide to create an amide bond, or an NHS ester derivative of the carboxylate, which can react directly with amines to form amide linkages. The three discussed in this section are representative of this amine-reactive BODIPY family. The two NHS ester derivatives react under alkaline conditions with primary amines in molecular targets to form stable, highly fluorescent derivatives. The carboxylate derivative can be coupled to an amine using the EDC/sulfo-NHS reaction discussed in Chapter 3, Section 1.2. 

Given that BuLi-TMEDA will deprotonate benzene , a similar coordination of BuLi with the substrate should be sufficient to allow the deprotonation of substituted aromatics. And indeed, amine 1, whose aromatic protons are no more acidic than those of benzene, is deprotonated rapidly (much faster than benzene) and regioselectively (at the 2-position, closest to the directing group) (Scheme 2) . 

Addition of a lithiated secondary amine to an aldehyde both protects the aldehyde from attack by RLi and turns it into an ortholithiation directing group. The best lithioamines for this purpose are A-lithio-A-methylpiperazine 53, iV-lithio-iV,iV,iV -trimethylethylene-diamine 56 and Al-lithio-Al,0-dimethylhydroxylamine 58 , which optimize the opportunity for coordination of BuLi to the intermediate alkoxide (54) (Scheme 27) . ... 

Methyl-3-phenylquinoxaline reacts with aryl aldehydes to form 2-styryl derivatives (124), but forcing conditions (reflux in oil bath for 12-15 hours) are necessary to overcome the steric effect of the 3-phenyl group.124 Direct N-amination of 2-phenylquinoxaline has been reported with O-mesitylsulfonylhydroxylamine. The reactive nitrogen is N-4, the least sterically hindered, and the product was characterized by conversion into the N-benzoylimine (125).132... 

The direct a-amination of aldehydes by azodicarboxylates as the electrophilic nitrogen source can be catalyzed by, for example i-proline 3a, to give the a-hydrazino aldehydes 4 having (R -configuration in moderate to good yields and with excellent enantioselectivities (89-97% ee) (Scheme 2.27) [4]. The optically active a-hydrazino aldehydes 4 are prone to racemization, and it was found beneficial to reduce them directly with NaBFU to stereochemical stable compounds which, by treatment with NaOH, can cyclize to form the N-amino oxazolidinones 5 in a one-pot process. The N-amino group in 5 could be cleaved with Zn/acetone to give the oxazolidinone 6 (Scheme 2.27). 

If the hydrogens of ammonia are replaced by alkyl or aryl groups, amines result. Depending on the number of carbon atoms bonded directly to nitrogen, amines are classified as either primary (one carbon atom), secondary (two carbon atoms), or tertiary (three carbon atoms) (Table 33.1). 

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