N-protected amine

The synthetic utility of this enantioselective alkylation of an arylimine rehes on a practical method for the dearylation of the resulting chiral amine. A two-step procedure was illustrated for amine 3a (R =Me), which begins with a protection step (n-BuLi/ClC02CH2Ph) followed by oxidative cleavage of the aryl moiety (ceric ammonium nitrate CAN). The N-protected amine 4a was isolated in only 58% overall yield without significant loss of enantiomeric purity (Scheme 3). 

Similar to the ether substrates mentioned above, both cyclic and acyclic N-protected amines could be converted into their corresponding ortho-C—H bond functionalization products via the insertion of metal carbenoids derived from Rh catalysts and donor/acceptor diazo compounds. Thking Af-Boc-protected pyrrolidine 48 as an example (Scheme 1.15), Rh2(S -DOSP)4 catalyzed the decomposition of methyl phenyldiazoacetate la and converted the Af-Boc-pyrrolidine 48 into the corresponding C—H bond insertion product 49 in 72% yield, 94% ee, and 92% de. Furthermore, the C2-symmetric amine 50 could be formed in 78% yield and 97% ee under altered reaction conditions. Further investigation demonstrates that this intermolecular C—H bond insertion could also be applied in the kinetic resolution of 2-substituted pyrrolidine 51. The corresponding C—H bond insertion reaction proceeded smoothly, and subsequent treatment with TFA delivered the deprotected product 52 in high diastereo- and enantioselectivity (45% yield, 91% ee, >94% de). " ... 

Bromobenzenesulfonyl chloride (BsCl) has been widely used to N-protect amines (eqs 1 and 2) Due to the relatively high molecular weight, p-bromobenzenesulfonyl derivatives have a higher melting point and may be more readily crystallizable than lower molecular weight derivatives. 

N-protected amines, which can be deprotected in situ, have also been extensively ntilized for the preparation of dialkylamines (Scheme 27). " ... 

The dibenzosuberyl ether is prepared from an alcohol and the suberyl chloride in the presence of triethylamine (CH2CI2, 20°, 3 h, 75% yield). It is cleaved by acidic hydrolysis (1 N HCl/dioxane, 20°, 6 h, 80% yield). This group has also been used to protect amines, thiols, and carboxylic acids. The alcohol derivative can be cleaved in the presence of a dibenzosuberylamine. ... 

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