Tandem Insertion of Halocarbenoids and Lithium Acetylides into Zirconacycles: A Novel Rearrangement to Zirconium Alkenylidenates by β-Addition to an Alkynyl Zirconocene

• Published in: Chemistry : a European journal 2011-04, Vol.17 (17), p.4896-4904
• Main Authors: Stec, Jozef, Thomas, Emma, Dixon, Sally, Whitby, Richard J.
• Format: Article
• Language: English
• Subjects: Alkynes - chemistry; carbenoids; carbocycles; Catalysis; Cyclopentanes - chemistry; Lithium - chemistry; metallacycles; Molecular Structure; Organometallic Compounds - chemical synthesis; Organometallic Compounds - chemistry; rearrangement; Stereoisomerism; zirconium; Zirconium - chemistry
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201002962

Tandem insertion of 1,1‐dihalo‐1‐lithio species (halocarbenoids) and lithium alkynides into zirconacyclopentenes and zirconcyclopentanes affords carbocyclic products in high yields via an unusual rearrangement that probably involves addition of an organolithium species to the β‐position of a zirconium–alkyne complex to give an alkenylidene–zirconate species. A wide variety of cyclopentanoid organic structures are rapidly assembled in good yield using this multicomponent coupling. The main side reaction, which becomes exclusive in some cases, is β‐hydride elimination of an intermediate cyclopentyl‐ or cyclopentenyl zirconocene. Zirconocene ‘ate’ complexes play several roles in a versatile three‐component one‐pot assembly of bicyclic organic structures from a 1,6‐ or 1,7‐enyne or ‐diene, an in situ generated halocarbenoid RCX2Li and a lithium acetylide. The most likely reaction pathway involves the unprecedented β‐addition of an organolithium species to an alkynyl zirconocene to give a zirconium alkenylidenate complex.