Von der basenkatalysierten Ringöffnung von 2 H ‐Azirinen zu einer α‐Alkylierungsmethode von primären Aminen

From a Base Catalyzed Ring Opening of 2 H ‐Azirines to an α‐Alkylation Method of Primary Amines It is shown that fluorene‐9′‐spiro‐2‐(3‐phenyl‐2 H ‐azirine) ( 1 ) on treatment with various alcohols in the presence of the corresponding alkoxide ions yields N ‐(9′‐fluorenyl)benzimidates 2a‐d (Scheme 1) . 2,2,3‐Triphenyl‐2 H ‐azirine ( 3 ) reacts with methanol in a similar manner (Scheme 2) . Benzimidates 2a (Scheme 3) , 8 (Scheme 4) and and 10 (Scheme 5) can easily be deprotonated by butyllithium (BuLi) or lithium diisopropylamide (LDA) in tetrahydrofuran (THF) to 1‐methoxy‐2‐aza‐allylanions, that can be alkylated, at C(3), exclusively, by various electrophiles ( e.g. R‐X(X = I, Br), RCHO or methyl acrylate (see also Scheme 6 )). As the acidic hydrolyses (1 N HCl) of benzimidates 9 and 11 leads to the corresponding α‐alkylated free amines 15 and 18 ( Scheme 7 and 8 ), benzoyl derivatives 16 and 19 are obtained from the hydrolysis under basic conditions. On the other hand, it is observed that a catalyzed Chapman rearrangement of 9 and 11 results in the formation of N ‐benzoyl‐ N ‐methyl derivatives 17 and 20 (Scheme 7 and 8) . The described reactions offer a simple method for the α‐alkylation of activated primary amines.