Benzyl amines selectivity

MAO is known to occur in at least two forms, MAO A and MAO B, based on substrate selectivity, inhibition by various dmgs, and cloning experiments. Clorgyline [17780-72-2] is a specific inhibitor of MAO A, which displays a substrate specificity for NE and serotonin. Deprenyl [2323-36-6] is a selective inhibitor of MAO B, and displays a substrate preference for P-phenylethylamine and benzyl amine. Dopamine and tyramine are substrates for both enzymes. 

Alcohols can be selectively bound to the same host type if they are combined with an amine and vice versa, considering that a cation and an anion will be formed through a proton transfer. The so-formed alkoxide anion will bind to the boron atom, while the ammonium ion will be complexed by the crown ether (147, Fig. 39). Competition experiments involving benzyl-amine have shown enhanced selectivity for the complexation of alcohols with... 

Since amines react more readily than alcohols in noncatalyzed reactions with anhydrides, the reaction is more difficult and initially required stoichiometric catalyst loadings [107], but could be performed in a catalytic sense with an O-acylated azlactone as acylating agent, which does not react with a benzylic amine at —50°C, but is capable of acylating the catalyst [108, 109]. Depending on the buUdness of the substrate, selectivities ranged from S = 11 to 27 (s = [ enantiomer l]/[ enantiomer 2])-... 

Reaction selectivity of the parent ortho-QM has also been explored with a variety of amino acid and related species.30 In these examples, the rates of alkylation and adduct yields were quantified over a range of temperatures and pH values. The initial QM3 was generated by exposing a quaternary benzyl amine (QMP3) to heat or ultraviolet radiation (Scheme 9.10). Reversible generation of QM3 was implied by subsequent exchange of nucleophiles at the benzylic position under alternative photochemical or thermal activation.30 Report of this work also included the first suggestion that the reversible nature of QM alkylation could be used for controlled delivery of a potent electrophile. 

The benzyl—nitrogen bond is not so easily cleaved as the benzyl—oxygen bond, unless the O-benzyl group is sterically hindered. This difference in activity allows the selective removal of the O-benzyl function in a molecule containing both N-benzyl and O-benzyl protecting groups. The selectivity can be reversed if the amine is protected by the Cbz group. If a small amount of amine (e g., butylamine) is added, then the selective removal of N-benzyl amines can be achieved.292... 

Murahashi, S.-I. Tamba, Y. Yamamura, M. Yoshimura, N. Reactions of cyclometalated Pd complexes with organolithium compounds or Grignard reagents. Selective ortho alkylation and arylation of benzaldehydes, azobenzenes, and tertiary benzylic amines. J. Org. Chem. 1978, 43, 4099-4106. 

The scope of the aromatic C-N bond formation extends beyond simple amine substrates. For example, selected imines, sulfoximines, hydrazines, lactams, azoles, carbamates, and amides all give useful products following aromatic C-N bond formation. In addition, allyl-amine undergoes arylation, providing an alternative to the ammonia surrogates benzyl-amine, tert-butyl carbamate, and benzophenone imine. Although it is an amine substrate, the reaction of this reagent is included here because of its special purpose. 

Aryl benzyl ethers are cleaved more easily than are alkyl benzyl ethers. The presence of an amine hinders the hydrogenolysis of alkyl benzyl ethers but has no effect on the cleavage of aryl benzyl ethers. - Because of this the benzyl ether is selectively hydrogenolyzed in compounds containing both a benzyl amine and an aryl benzyl ether (Eqn. 20.24)55 but the benzyl amine is selectively cleaved in compounds having both a benzyl amine and an alkyl benzyl ether (Eqn. 20.25).53,54,56... 

Reductive alkylation of amines. Selective benzylation of terminal amino groups of a polyamine is achieved by NaBH reduction of the derived Schiff bases. 

A-Alkylation Reactions. The 9-BBN complexes of diamines such as 1,8-diaminonaphthalene and 2-aminobenzylamine serve as substrates for selective iV-alkylation. N-chelated borane complexes undergo regioselective mono-(V-alkylation with an alkyl halide under basic conditions without further alkylation. Hydrolysis of the corresponding intermediate provides the mono-iV-alkyl-ated product in excellent yields (eq 53). In this case, the 9-BBN chelation of the diamine both protects the aromatic amine and activates the benzylic amine. 

Lee and co-workers used 2,4-dichloroquinazolines in their development of 4-benzylamino phosophdiesterase (PDE) inhibitors. Treatment of 2,4-dichloro-6-((triisopropylsilyl)ethynyl)quinazoline with benzyl amine under thermal conditions gave the corresponding 4-substituted product selectively. A yield was not reported for this reaction. 

Although this type of catalyst was highly active and selective for the race-misation of benzylic amines, the reaction times for DKR were still longer than 24 hours in some cases and small amounts of side products were formed. In order to improve the performance of these palladium catalysts, the group employed microwave irradiation as a heating source, demonstrating that racemisation reactions of benzylic amines under microwave irradiation catalysed by Pd/CaCOs were faster and more selective. Furthermore, they checked that the microwave irradiation had no influence on the activity and... 

The most general and selective method to perform stereoselective intermolec-ular C—H amination is based on the use of a chiral sulfonimidamide reagent with Rh2[(S)-nta]4 as catalyst [69, 70]. Muller, Dodd, Dauban and coworkers have developed such a reagent. Equimolar amounts of alkane and nitrogen precursor are used in the presence of 1.4 equiv of di-tert-butylacetoxyiodobenzene and 3 mol % of the rhodium catalyst. The reaction is typically run at —35°C for 3 days. Benzylic amines are obtained in 14 1 to 200 1 dr and allylic amines are formed in 3 1 to 19 1 dr both products are produced in good to excellent yields (Eqs. (5.16) and 5.17). 

In further optimizations, Beller and coworkers examined various benzyl amines as replacement for pyrrolidine in the FeCl3-H2pydic catalyst system. They found thatthe use of different benzyl amines resulted in higher yields and better selectivity for the formation of epoxides, predominantly from aliphatic alkenes [111]. As seen in Table 2.8, the epoxidation of trans-l,2-disubstituted alkenes such as frans-2-octene and fruns-5-decene resulted in high yields, whereas aliphatic terminal alkenes appear to be problematic substrates. The epoxidation of aromatic alkenes using this catalytic system gave similar results to those obtained using pyrrolidine as base. 

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