title: Highly selective Barbier-type propargylations and allenylations catalyzed by titanocene(III).
abstract: The alkyne functional group is found in many bioactive natural products and is the key to many important chemical transformations developed over recent years. Moreover, allenes have recently gained relevance as versatile reagents in organic synthesis. Mild, catalytic methods to enable the selective introduction of either alkyne or allene motifs into organic molecules are very valuable but, as yet, quite scarce. We describe an extremely mild and selective method for either the propargylation or allenylation of carbonyl compounds catalyzed by the abundant, safe, and inexpensive metal titanium. These reactions can selectively provide homopropargylic alcohols from aldehydes and ketones or α-hydroxy-allenes from aldehydes. The mechanisms involved were also investigated.
authors.affiliation: Department of Organic Chemistry, University of Granada, Faculty of Sciences, Campus Fuentenueva s/n, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Muñoz-Bascón
authors.forename: Iris
authors.initials: I
authors.lastname: Sancho-Sanz
authors.forename: Enrique
authors.initials: E
authors.lastname: Álvarez-Manzaneda
authors.forename: Antonio
authors.initials: A
authors.lastname: Rosales
authors.forename: J Enrique
authors.initials: JE
authors.lastname: Oltra
mesh_terms: D000438:Alcohols / Q000138:chemical synthesis / Q000737:chemistry; D000447:Aldehydes / Q000737:chemistry; D000466:Alkadienes / Q000138:chemical synthesis / Q000737:chemistry; D000480:Alkynes / Q000737:chemistry; D002384:Catalysis; D007659:Ketones / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry*
chemical_list: D000438:Alcohols; D000447:Aldehydes; D000466:Alkadienes; D000480:Alkynes; D007659:Ketones; D009942:Organometallic Compounds; C406884:titanocene; C025947:propadiene