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Facile and convenient synthesis of functionalized propargylic alcohols and amines: an InBr3-Et3N reagent system promotes the alkynylation of aldehydes and N,O- or N,S-acetals

Norio Sakai*, Reiko Kanada, Maki Hirasawa and Takeo Konakahara

*Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan, Email: sakachemrs.noda.tus.ac.jp

N. Sakai, R. Kanada, M. Hirasawa, T. Konakahara, Tetrahedron, 2005, 61, 9298-9304.

DOI: 10.1016/j.tet.2005.07.059



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Abstract

A novel InBr3-Et3N reagent system promotes the alkynylation of not only a variety of aromatic/heterocyclic or bulky aliphatic aldehydes but also N,O- or N,S-acetals. The reaction of N-silyl-N,O-acetals with 1-alkynes gives primary propargylic amines in good yields.

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Details

The document describes a study on the synthesis of functionalized propargylic alcohols and amines using an InBr3–Et3N reagent system. This system promotes the alkynylation of various aromatic, heterocyclic, and bulky aliphatic aldehydes, as well as N,O- and N,S-acetals. The research highlights the efficiency of the InBr3–Et3N system in producing propargylic alcohols and amines under mild conditions. The study initially optimized the reaction conditions using phenylacetylene and benzaldehyde, finding that InBr3 in diethyl ether yielded the best results. The method was then applied to a range of aldehydes and alkynes, demonstrating high yields and broad applicability. Additionally, the system was effective in synthesizing primary propargylic amines directly from N-silyl-N,O-acetals. The proposed mechanism involves the coordination of InBr3 with the alkyne, facilitating proton abstraction and subsequent nucleophilic addition to the aldehyde. The study concludes that the InBr3–Et3N system is a versatile and efficient method for synthesizing propargylic alcohols and amines, with potential applications in the preparation of biologically active compounds. Further investigations into the reaction mechanism are ongoing.


Key Words

Alkynylation, Propargylic alcohols, Propargylic amines, Indium bromide, Acetals


ID: J72-Y2005-3070