Aryl Azide-Allene Cycloaddition. The Contrasting Behavior of Two Simple Allenes, 1,2-Cyclononadiene and 1,2-Propadiene

Article abstract of DOI:10.1021/jo00014a026

1,2-Cyclononadiene (1) reacts with phenyl azide (2a) and 4-bromophenyl azide (2b) to give conjugated triazoline adducts 3a and 3b, respectively. (R)-(+)-1 and 2a react to give (S)-(+)-3a, which is consistent with a concerted cycloaddition mechanism.The reaction of 1,2-propadiene (6) and 2a gives triazoles 8 and 10 plus compound 18 in nearly equal amounts.The formation of these products is rationalized by a scheme involving initial formation of triazolines 7 and 9.Triazoline 3a is slowly isomerized by sodium ethoxide or N,N-dimethylaniline to triazole 20.