Synthesis of spiro[pyrrolidine or piperidine-3,9′-xanthenes] by anionic cycloacylation of carbamates

Xanthene spiropyrrolidines and spiropiperidines were synthesized by a process in which the key step was intramolecular trapping of a xanthen-9-yl anion by a carbamate side-chain situated at the same position.