Synthesis of N,N-Bicyclic Pyrazolidinones Using Cu(OH)_x/Al₂O₃

Significance

Alumina-supported copper hydroxide [Cu(OH)_x/Al₂O₃] catalyzed the 1,3-dipolar cycloaddition of azomethine imines 1 with terminal alkynes 2 to give the corresponding N,N-bicyclic pyrazolidinones 3 in 55-98% yield (11 examples). In the formation of 3a, the catalyst was recovered by simple filtration and reused twice without significant loss of its catalytic activity (1^st reuse: 94% yield, 2^nd reuse: 93% yield).