title: Retropinacol/cross-pinacol coupling reactions--a catalytic access to 1,2-unsymmetrical diols.
abstract: Unsymmetrical 1,2-diols are hardly accessible by reductive pinacol coupling processes. A successful execution of such a transformation is bound to a clear recognition and strict differentiation of two similar carbonyl compounds (aldehydes → secondary 1,2-diols or ketones → tertiary 1,2-diols). This fine-tuning is still a challenge and an unsolved problem for an organic chemist. There exist several reports on successful execution of this transformation but they cannot be generalized. Herein we describe a catalytic direct pinacol coupling process which proceeds via a retropinacol/cross-pinacol coupling sequence. Thus, unsymmetrical substituted 1,2-diols can be accessed with almost quantitative yields by means of an operationally simple performance under very mild conditions. Artificial techniques, such as syringe-pump techniques or delayed additions of reactants are not necessary. The procedure we describe provides a very rapid access to cross-pinacol products (1,2-diols, vicinal diols). A further extension of this new process, e.g. an enantioselective performance could provide a very useful tool for the synthesis of unsymmetrical chiral 1,2-diols.
authors.affiliation: Department of Chemistry, Humboldt University of Berlin.
authors.forename: Ulf
authors.initials: U
authors.lastname: Scheffler
authors.affiliation: Department of Chemistry, Humboldt University of Berlin; rainer.mahrwald@rz.hu-berlin.de.
authors.forename: Rainer
authors.initials: R
authors.lastname: Mahrwald
mesh_terms: D000438:Alcohols / Q000138:chemical synthesis*; D000447:Aldehydes / Q000737:chemistry*; D002384:Catalysis; D007659:Ketones / Q000138:chemical synthesis; D010084:Oxidation-Reduction
chemical_list: D000438:Alcohols; D000447:Aldehydes; D007659:Ketones
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