Transition metal free catalytic terminal alkyne functionalization across the C-X triple bond (X = CH, N): E-Selective dimerization under ambient conditions

Swain, Asim Kumar (2019) Transition metal free catalytic terminal alkyne functionalization across the C-X triple bond (X = CH, N): E-Selective dimerization under ambient conditions. Masters thesis, Indian Institute of science Education and Research Kolkata.

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Abstract

Herein we report a completely transition metal free and ligand free method using KOtBu as a catalyst for alkyne functionalization under ambient condition. Complexation of K⁺ ion either with a strong coordinating solvent (DMSO) or a strong coordinating agent (18- crown-6) enhances the basicity of KOtBu which was utilized for proton abstraction of terminal arylalkyne to initiate the alkyne dimerization process. Transition state calculation reveals that a weak non-covalent interaction between K⁺ ion and aromatic anionic π-electron cloud facilitates Z- to E- isomerization resulting in E-selective 1, 3-enyne products at room temperature which was so far accomplished by transition metal-based catalyst. Furthermore, this catalytic protocol was successfully extended for functionalization of alkyne with nitrile in accomplishing the first transition metal free α, β-alkynyl N-H ketimine preparation by direct reaction between nitrile and alkyne.

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