Benzamides, to protect amines

Reduction of the N-N bond of 2 proceeded smoothly with freshly prepared Sml. After reductive methylation, hydrogenation removed the benzyl ether, and AIH3 converted the benzamide to the benzyl amine. At low temperature, mesylation of the alcohol was apparently faster than mesylation of the secondary amine, enabling cycUzation to 14. Removal of the benzyl protecting group gave Nankakurine A, which was successfully methylated to give Nankakurine B. 

When a C2 spacing group is required to be C-functionalised, the most obvious precursor is an a-amino acid derivative. Such a strategy has been developed for the synthesis of the [9]-N3 and [12]-N4 derivatives 8,9 and 10. Both 8 and 9 were synthesised from (25)-lysine16 while 10 has been prepared from the enantiopure p-nitrophenylalanine.17 In the synthesis of the [9]-N3 derivative, a key step (Scheme 1.11) involved protection of the diethylenetriamine moiety by copper(II) prior to selective acylation of the terminal primary amine and subsequent Richman-Atkins8 cyclisation. Detosylation was effected with concentrated sulfuric acid, leaving the benzamide intact. 

Aliphatic amine derivatives such as amides, carbamates and sulfonamides also participate in Pd - catalyzed intramolecular C-N bond formation. The relative reactivity of these amino nucleophiles toward cyclization has been evaluated in the PdCL-catalyzed cyclization of iV-protected 4-pentenylamines and 5-hexenylamines, and it was found to be urea > carbamate > tosylamide > benzamide. The PdCl2(CH3CN)2-catalyzed dehydrative cyclization of alkenyl urethanes bearing an allylic hydroxyl group has been elegantly applied to the synthesis of chiral piperidine alkaloids. The cyclization reaction occurs with complete stereocontrol in good yields in the presence of 15-20 mol % of catalyst without any reoxidant (eq 16). 

The first example of olefinic C-H addition to iV-sulfonylaldimines and aryl aldehydes has been achieved through olefinic C-H bond activation by a rhodium complex. C-H bond functionalization by Rh(III) catalysts has also been used to achieve arylation of N-protected aryl aldimines by 2-arylpyridine and benzamide mechanistic studies have provided insight for further development of this means of creating a-branched amine functionality. A cobalt-A-heterocyclic carbene (NHC) catalyst has also directed arylation of aromatic aldimines through C-H bond functionalization of 2-arylpyridines. ... 

Protection of Alcohols as Benzoates and of Amines as Benzamides. PhCOCI easily reacts with alcohols to give the corresponding benzoates in excellent yields. The acylation is NHCOPh performed in the presence of an amine, very often pyridine or tri-... 

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