2- amino pyridine-type amines

In one prominent example such an unexpected reaction product was observed in three research laboratories independently. During attempts to synthesize a library of Ugi-type four-component products using various isonitriles, aldehydes, acids and amines the reaction did not gave the desired Ugi-type four-component reaction product when amino pyridine-like starting materials were used as the amine component. In the case of such 2-amino pyridine-type amines the clean formation of... 

Publications on other types of rearrangements involving tetrazoles are cited at length in a review <2004SOS(13)861> in particular, the Smiles rearrangement of 2-[(l-alkyl/aryl-17/-tetrazol-5-yl)sulfanyl]pyridine-3-amines 208 to 3-[(l-alkyl/aryl-l/7-tetrazol-5-yl)amino]pyridine-2(l/f)-thiones 209 under acidic conditions and Smiles rearrangement of 5-sulfanyl/sulfone-substituted tetrazoles 210 to tetrazol-5-amines 211 under basic conditions (Scheme 19) <2004SOS(13)861>. 

Corrections are applied to 15 structural types (e.g., alcohols/acids selected phenols, nitros, amines, alkyl pyridines, amino acids, PAHs, multi-nitrogen types, etc.). Application and magnitude depend on available MP. 

Transition-metal-catalysed reactions can be used to introduce aryl or heteroaryl groups onto the ring NH, or attached amino groups, of heterocycles. They can also be used for the displacement of leaving groups by amines in all types of heterocyclic systems, including the use of milder conditions for substitutions at relatively activated positions, such as a- and y-positions in pyridines, where nucleophilic substitutions can be carried out. 

Phenol-type resins 13-15 have also been used to prepare LH-RH, enkephalin and bradykinin peptide analogs. Peptides were successfully cleaved by ammonoly-sis (NH3 in MeOH-DMF or DMF, 5-18h) or aminolysis with protected amino acid or peptide esters bearing the free a-amino group [24, 25, 35]. Marshall s mercaptophenol resin (16) has been used to prepare libraries of piperazine-2-carboxamides (consisting of 22 different amines) and 6-carboxybenzopyran-4-ones. Cleavage was performed using an excess of appropriate amines in pyridine for 24 to 48 h [36, 37]. Tetrahydro-P-carboline-3-carboxamides have also been similarly synthesized and released [38]. 

The nitrogen-containing bases are derivatives of three families of heterocyclic compounds called the pyrimidines, purines, and pyridines. Here, the kinship with amine- or amino-type compounds becomes apparent. 

Several ring-fused tetrazole compounds have been reported. 2-Methyl-3-cyanopyridines were converted into their corresponding 2-azidomethyl derivatives, which underwent intramolecular cycloaddition reactions to give 3-(tetrazol-5-yl)pyridines 186 <04TL9127>. Fused tetrazole derivatives 187 were obtained via tandem cycloaddition and yV-allylation reactions <04JOC1346>. Expeditive synthesis of homochiral fused tetrazole piperazines 188 from 3-amino alcohols has been reported <04TL3725>. A novel Ugi-five-center-four-component reaction (U-5C-4CR) of aldehydes, primary amines, trimethylsilyl azide and 2-isocyanoethyl tosylate afforded tetrazolopiperazine type compounds <04TL6421>. 

---