Electrophile Aminierung von C‐H‐aciden Verbindungen mit 1‐Oxa‐2‐azaspiro[2.5]octan

Electrophilic Amination of C‐H‐Acidic Compounds with 1‐Oxa‐2‐azaspiro[2.5]octane The reactions of 1‐oxa‐2‐azaspiro[2.5]octane ( 1 , 3,3‐pentamethyleneoxaziridine) with malonic (e.g. 4 , 35 ) and cyanoacetic acid derivatives (e.g. 11 , 13 20 ) and other C‐H acids [e.g. barbituric acid ( 6 ), Meldrum's acid, (diphenylmethyleneamino)‐acetonitrile ( 26 ) 1‐benzyl‐3‐hydroxy‐4‐methyl‐1 H ‐pyrazol‐5(4 H )‐one, and phenylbutazone ( 33 )] have been studied. After the introduction of a 1‐hydroxycyclohexylamino group at the acidic position, five different stabilisation reactions of the intermediate 2 could be classified. The most important one is an intramolecular nucleophilic attack to a nitrile group giving disubstituted 1,4‐diazaspiro[4.5]decanones 2a . Their ring transformations (e.g. 2a → 3 ) or the introduction of a second amino group at the same carbon atom ( 2a → 3a ) are further new reactions. Geminal diamino acid derivatives 3a thus obtained can be stable or rearrange to 3 (R 1 NH 2 ) or eliminate cyclohexanone (formation of 42 ) and/or ammonia (formation of 41 or 43 ). Amination of N ‐cyanoacetyl‐protected amino acid esters ( 20 , NHR = amino acid unit) with 1 yields cyclic dipeptide derivatives 41 .