Double 1,4-addition of malonate to 1,2-diaza-1,3-butadienes: a useful route to previously unknown symmetric and unsymmetric 1,6-dioxo-2,7-diazaspiro[4.4]nona-3,8-dienes
Double 1,4-addition of malonate to 1,2-diaza-1,3-butadienes: a useful route to previously unknown symmetric and unsymmetric 1,6-dioxo-2,7-diazaspiro[4.4]nona-3,8-dienes