Borinic Acid Catalyzed Regioselective N-Alkylation of Azoles
Shrey P Desai1, Matthew T Zambri1, Mark S Taylor1
1Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
Abstract:
A method for regioselective N-alkylation of ambident, azole-type heterocycles with alkene or epoxide electrophiles is described. In the presence of diphenylborinic acid (Ph2BOH) and an amine cocatalyst, heterocyclic nucleophiles such as 1,2,3- and 1,2,4-triazoles, substituted tetrazoles, and purine are activated toward selective N-functionalization. The scope of electrophilic partners includes enones, 2-vinylpyridine, phenyl vinyl sulfone, a dehydroalanine derivative, and epoxides. Mechanistic studies, including in situ 11B NMR spectroscopy and kinetic analysis, are discussed.
Related Concept Videos
Preparation of 1° Amines: Azide Synthesis
Azide ions act as good nucleophiles and react with unhindered alkyl halides to form alkyl azides. Alkyl azides do not participate in further nucleophilic substitution reactions, thereby eliminating the chances of polyalkylated products. Alkyl azides are reduced by hydride-based reducing agents, like lithium aluminum...
Regioselectivity and Stereochemistry of Hydroboration
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn...
Nucleophilic Aromatic Substitution of Aryldiazonium Salts: Aromatic SN1
In the Sandmeyer reaction, for example, the diazonio group is replaced by a chloro, bromo,...
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
Hydroboration-Oxidation of Alkenes
α-Alkylation of Ketones via Enolate Ions


