From an Amine

Note. Useful information can often be obtained by adding (i) dilute H,SO or (ii) dilute NaOH solution to an aqueous solution of the substance under investigation. A precipitate with (i) usually indicates an aromatic carboxylic acid from a metallic or from an ammonium salt. A precipitate or oil with (ii) usually indicates an aromatic amine from an amine salt. 

Cope Elimination- elimination of R2NOH from an amine oxide... 

One extra disconnection is all we need to cope with misaturated heterocycles. If a nitrogen atom is joined to a double bond in a ring, we have a cyclic enamine. This is made from an amine and a carbonyl compound in the same way as ordinary enamines ... 

Caibamates ate formed from an amine with a wide variety of reagents, of which the chloroformate is the most common amides are formed from the acid chloride. -Alkyl caibamates are cleaved by acid-catalyzed hydrolysis A/-alkylamides are cleaved by acidic or basic hydrolysis at teflux. conditions that cleave peptide bonds. 

This amide, readily formed from an amine and the anhydride, is readily cleaved by penicillin acylase (pH 8.1, A -methylpyrrolidone, 65-95% yield). This depro-tection procedure works on peptides as well as on nonpeptide substrates. 

The imine, prepared from an amine and (C5H4N)(Me3C JH2)CO (TiC, toluene, reflux, 12 h NaOH, 80% yield), can be cleaved with coned. HCl (reflux). The protective group was used to direct a-alkylation of amines. 

Sulfenamides, R2NSR, prepared from an amine and a sulfenyl halide, " are readily cleaved by acid hydrolysis and have been used in syntheses of peptides, penicillins, and nucleosides. They are also cleaved by nucleophiles, and by Raney nickel desulfurization. ... 

Sulfonamides (R2NSO2R ) are prepared from an amine and sulfonyl chloride in the presence of pyridine or aqueous base. The sulfonamide is one of the most stable nitrogen protective groups. Arylsulfonamides are stable to alkaline hydrolysis, and to catalytic reduction they are cleaved by Na/NH3, Na/butanol, sodium naphthalenide, or sodium anthracenide, and by refluxing in acid (48% HBr/cat. phenol). Sulfonamides of less basic amines such as pyrroles and indoles are much easier to cleave than are those of the more basic alkyl amines. In fact, sulfonamides of the less basic amines (pyrroles, indoles, and imidazoles) can be cleaved by basic hydrolysis, which is almost impossible for the alkyl amines. Because of the inherent differences between the aromatic — NH group and simple aliphatic amines, the protection of these compounds (pyrroles, indoles, and imidazoles) will be described in a separate section. One appealing proj>erty of sulfonamides is that the derivatives are more crystalline than amides or carbamates. 

Tosylates are generally formed from an amine and tosyl chloride in an inert solvent such as CH2CI2 with an acid scavenger such as pyridine or triethylamine. 

The DNMBS derivative, readily prepared from an amine and the sulfonyl chloride, is efficiently (0 = 0.65) cleaved photochemically hv >300 nm, EtOH, NH3 BH3, 77-91% yield). " ... 

This amide, readily formed from an amine and the anhydride or enzymatically using penicillin amidase, is readily cleaved by penicillin acylase (pH 8.1, A -methylpyrrolidone, 65-95% yield). This deprotection procedure works on peptides, phosphorylated peptides, and oligonucleotides, as well as on nonpeptide substrates. The deprotection of racemic phenylacetamides with penicillin acylase can result in enantiomer enrichment of the cleaved amine and the remaining amide. An immobilized form of penicillin G acylase has been developed. ... 

Preparation from an amine and TMSCHN2 (HBF4, CH2CI2, H2O) has also been explored. 

DDQ is often used to remove the MPM group from alcohols and can be used to cleave it from an amine, but in the following case overoxidation also occurs ... 

The dibenzosuberylamine is prepared in quantitative yield from an amine or amino acid and suberyl chloride this chloride has also been used to protect hydroxyl, thiol, and carboxyl groups. Although the dibenzosuberylamine is stable to 5 A HCl/dioxane (22°, 16 h) and to refluxing HBr (1 h), it is completely cleaved by some acids (HCOOH, CH2CI2, 22°, 2 h CE3COOH, CH2CI2, 22°,... 

The DNMBS derivative, readily prepared from an amine and the sulfonyl... 

The preparation of an alkene 3 from an amine 1 by application of a /3-elimination reaction is an important method in organic chemistry. A common procedure is the Hofmann elimination where the amine is first converted into a quaternary ammonium salt by exhaustive methylation. Another route for the conversion of amines to alkenes is offered by the Cope elimination. 

Changing the functionality on the alicyclic ring from an amine to a carboxylic acid leads to a compound that shows antiallergic activity, acting possibly by means of inhibition of the release of allergic mediators. Thus, condensation of acylated indole with cyclohexanone carboxylic acid affords directly oxarbazole (29). ... 

Exciplexes are complexes of the excited fluorophore molecule (which can be electron donor or acceptor) with the solvent molecule. Like many bimolecular processes, the formation of excimers and exciplexes are diffusion controlled processes. The fluorescence of these complexes is detected at relatively high concentrations of excited species, so a sufficient number of contacts should occur during the excited state lifetime and, hence, the characteristics of the dual emission depend strongly on the temperature and viscosity of solvents. A well-known example of exciplex is an excited state complex of anthracene and /V,/V-diethylaniline resulting from the transfer of an electron from an amine molecule to an excited anthracene. Molecules of anthracene in toluene fluoresce at 400 nm with contour having vibronic structure. An addition to the same solution of diethylaniline reveals quenching of anthracene accompanied by appearance of a broad, structureless fluorescence band of the exciplex near 500 nm (Fig. 2 )... 

Nolte and coworkers reported on the formation of micelles with a helical superstructure from AB amphiphilic diblock copolymers prepared from an amine-end-capped polystyrene that was used as the initiator for the polymerization of various dipeptide-derived isocyanides (Fig. 16). 

A well-known example of an exciplex is the excited-state complex of anthracene and N,N-diethylaniline resulting from the transfer of an electron from an amine molecule to an excited anthracene molecule. In nonpolar solvents such as hexane, the quenching is accompanied by the appearance of a broad structureless emission band of the exciplex at higher wavelengths than anthracene (Figure 4.9). The kinetic scheme is somewhat similar to that of excimer formation. 

The reaction pathways by which the net transfer of a hydrogen atom from an amine to a photoexcited ketone has been extensively examined in the nanosecond [23, 25-30], picosecond [20, 22, 31-33], and femtosecond [24] time domains. The following mechanism, as it pertains to the photochemical reduction of benzophenone (Bp) by N, A-dimethylaniline (DMA), is derived from these numerous studies. Only an overview of the mechanism will be presented. The details of the studies leading to the mechanism will not be given for specifics, the reader is referred to the original literature. 

Photodegradation of DDT by the protease-liberated flavo-protein from TX-20 resulted in the formation of TDE as the major product in addition to three other minor compounds. It has been well established that DDT conversion to TDE, anaerobically, is a reductive process involving replacement of a chlorine atom by hydrogen. On the other hand, it has been suggested that photo-lytic reactions involve a charge transfer from an amine to DDT and a subsequent pickup of a proton. Thus there is a possibility that the photochemical reaction involving flavoproteins undergoes a similar reaction scheme. Much more data are, however, needed to confirm this point. 

On the other hand, we also planned alternative completely new approach (Route B) to Nakadomarin A, which involves the spirolactam followed by coupling reaction with furan derivative and subsequent intramolecular electrophilic substitution reaction of an iminium cation generated from an aminal to give highly functionalized tetracyclic core system (Scheme 10.3). 

Ammonium ion a cationic species derived from an amine by the addition of a proton or alkyl group e.g., ammonium ion itself, NH. ... 

Hydrolysis of the new imine then allows formation of a ketone as part of an a-keto acid, and an amine which is the previously mentioned pyridoxamine 5 -phosphate. Since this imine is the product from an amine and a ketone, it is termed a ketimine. These reactions are reversible in nature, allowing amino acids to be converted into keto acids, and keto acids to be converted into amino acids (see Section 15.6). 

A reaction commonly developed in the discovery lab is removing a Boc group from an amine using trifluoroacetic acid (TEA). Because TEA is highly corrosive, difficult to contain and recover (bp 72°C), and poses incineration problems due to the generation of HE, alternative conditions are usually explored for scale-up. Strong acids used instead of TEA include HCl, H2SO4, methanesulfonic acid, and toluenesulfonic acid... 

It has been suggested that ethane (3) may also be formed from an amine. 

Another interesting example of an insertion reaction is found through the addition of benzophenone to complex 59 (Scheme 15). In this case hydrogen is abstracted from an amine group with addition of an alkyne unit across the carbonyl to produce a radical anion. 

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