2-Amino- -imin

Bis-imine werden im alkalischen Medium ebenfalls nur bis zur Amino-imin- bzw. En-diamin-Stufe reduziert7 ... 

Scheme 23 Double asymmetric induction in the addition of Grignard reagents to chiral a-amino imines and a-amino iminium ions...

Scheme 30 Substrate-induced diastereoselective reductions of a-aminooximes and a-amino imines...

By an analogous route, the cyclization of chiral (z-amino imines 197, bearing the proper tw-functionality in the o -alkyl chain, will lead to 3-substituted 1,2-diaminocycloalkanes 198. The intermolecular and intramolecular addition of allylic silicon and tin compounds to a-amino azomethine compounds should also be investigated. 

The reductive amination of ketones can be carried out under hydrogen pressure in the presence of palladium catalysts. However, if enantiopure Q -aminoketones are used, partial racemization of the intermediate a-amino imine can occur, owing to the equilibration with the corresponding enam-ine [102]. Asymmetric hydrogenation of racemic 2-amidocyclohexanones 218 with Raney nickel in ethanol gave a mixture of cis and trans 1,2-diamino cyclohexane derivatives 219 in unequal amounts, presumably because the enamines are intermediates, but with excellent enantioselectivity. The two diastereomers were easily separated and converted to the mono-protected cis- and trans- 1,2-diaminocyclohexanes 220. The receptor 221 has been also synthesized by this route [103] (Scheme 33). 

In 2004, Kobayashi et al. introduced enecarbamates as nucleophiles to asymmetric catalysis [48], The addition of enecarbamates to imines in the presence of a chiral copper complex provides access to P-amino imines which can be hydrolyzed to the corresponding p-amino carbonyl compounds [49],... 

Aminopyrazolopyrimidines exist in the amino form. The only exception is 7-aminopyrazolo[l,5-a]pyrimidine, which exists in the solid state as an amino-imine mixture. The evidence is not conclusive (70BCJ849). Previous work on the same series has assigned an amino structure (62CPB620). Other aminopyrazolo[l,5-a]pyrimidines investigated were shown to exist in the amino form (74JHC423). 

Tetra-r-butylpyridazine (34) is converted into its Dewar isomer (35) when irradiated in pentane with UV light of wavelength > 300 nm. Irradiation of this product at shorter wavelengths, or thermolysis, gives rise to further reaction (91TL57). Irradiation of 4-amino-2,6-dimethylpyrimidine gives the acyclic amino imine via the Dewar pyrimidine as shown in Scheme 2a. The photoisomerization of perfluoropyridazines to pyrazines is considered also to involve Dewar diazine intermediates. 

Addition of any amino group to give, via aminal [5], amino imine 7 (scheme 2). 

This last point has been examplified through transimination reactions and ring-chain tautomerism between cyclic aminals and open chain amino imines. 

Diamine 8 is obtained from hydrogenation of amino imine 7 which can be formed by direct addition of primary amine to amino imine [1] or to l-aza-l-cycloheptene 3. 

Metal template syntheses of complexes incorporating the p-amino imine fragment have been introduced by Curtis as a result of his discovery that tris(l,2-diaminoethane)nickel(II) perchlorate reacted slowly with acetone to yield the macrocyclic complexes (40) and (41) (equation 8).81-83 In this macrocyclic structure the bridging group is diacetone amine imine, arising from the aldol condensation of two acetone molecules. This reaction is widely general, in the same way that the aldol reaction is, and can be applied to many types of amine complexes. The subject has been reviewed in detail with respect to macrocyclic complexes by Curtis.84... 

P-Amino imine complexes can also be synthesized from template reactions of p-amino ketones and amines. This approach has been applied to the amino ketone (45), which can be formed by acidic hydrolysis of a zinc(II) macrocyclic complex (Scheme 9).94-95... 

The tautomerism of 4-aminopyrazolo[3,4-J]pyrimidines as well as aminopyrazolo[4,3-d]py-rimidines has been investigated. 4-Aminopyrazolo[3,4-J]pyrimidines exist in water in two tautomeric forms l//-4-amino (85) and 2//-4-amino (86) [K (86/85) = 0.1 at 100°C AH = 9.0 kcal, mol ]. Interconversion of these two forms is catalyzed by acid or base <77JA7257, 80ZN(C)878, 82MI 712-02). Together with these two predominant species there are smaller proportions of the 7//-4-amino (87) (1 x 10-3) and the 5//-4-amino isomer (2 x 10-4). The species (87) exists only as an amino tautomer whereas the 5//-4-amino species in water has a partial imino structure (amino/imine =10) <77JA7257>. 

An interesting example of a system where both amino-carbonyl and amino-imine cyclizations occur involves the biisoxazolyl (103), which on catalytic hydrogenation followed by cyclization gives the pyridones (104) and (105).238... 

Kobayashi and coworkers pioneered the use of enamides or enecarbamates as nucleophiles in enantioselective reactions with either glyoxylates or glyoxylate derived imines catalyzed by chiral copper complexes [65]. The reaction using enamides or enecarbamates as nucleophilic components, namely, the aza ene reaction, with imines provides P amino imines that can be readily transformed into... 

Cyclization of a 6-amino imine with an aldehyde yields a tetrahydropyrimidine. At the hydroxylamino level the 1,2,5,6-tetrahydro-l-pyrimidinol 3-oxide (538) was formed. Mn02 oxidation gave the 1,3-dioxide (539) in 56% yield. Without substituents, the yield of pyrimidine 1,3-dioxide was 8% <75TL2721>. 

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