Stable bicyclic, monocyclic and aromatic azomethine ylides 1, 13 and 16 add angle-strained, electron-rich and electron-poor alkynes as well as alkenes and heterocumulenes to form 1:1-adducts in highly stereoselective 1,3-dipolar cycloadditions. Unsymmetrical dipalarophiles react in a regiospecific manner. (C) 2000 Elsevier Science Ltd. All rights reserved.
3,4-Diazanorcaradienes and 4,5-dihydropyridazines as precursors for new stable azomethine ylides
The synthesis of a new class of stable coloured azomethineylides 3 derived from 3,4-diazanorcaradienes is reported, which under acid catalysis are transformed to again coloured stable azomethineylides 4 containing a five-membered 1-aza-1,3-cyclopentadiene skeleton. Azomethineylides 3 in boiling methanol rearrange to 3,5-diazahomotropilidenes 8 in good yields.