Metal‐Catalyzed [1,2]‐Alkyl Shift in Allenyl Ketones: Synthesis of Multisubstituted Furans

Even fused furans can be prepared by cycloisomerization of substituted allenyl ketones. The cascade reaction involves a [1,2]-migration of alkyl or aryl groups in allenyl ketones as the key step. Facile reaction in the presence of cationic complexes, as well as migratory aptitude in the cycloisomerization of unsymmetrically substituted allenes, strongly supports an electrophilic mechanism for this transformation.