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Synlett
DOI: 10.1055/a-2744-2097
Letter
Published as part of the Special Topic Alkynes in Organic Synthesis

Influence of Nitrogen Atom on Alkynyl Benzoate Donor Reactivity: 3-(Phenyl Ethynyl) Picolinates as Stable and Reactive Glycosyl Donors Toward Stereoselective Glycoside Bond Formation

Authors

  • Rajesh Lenka

    1   Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, India (Ringgold ID: RIN28678)

  • Sangay Moktan

    1   Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, India (Ringgold ID: RIN28678)

  • Mahendra K. Rotta

    1   Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, India (Ringgold ID: RIN28678)

  • Pavan K. Kancharla

    1   Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, India (Ringgold ID: RIN28678)

PKK is thankful to SERB (DST, New Delhi) for the financial assistance through CRG/2023/002033 and the Ministry of Energy India for STARS-2/2023-0671. RL and SM thanks IITG for the fellowship, MKVR thanks UGC for the fellowship.
Supported by: IIT Guwahati, Department of chemistry SR/FST/CS-II/2017/23C
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Graphical Abstract

Abstract

We have demonstrated the development of 3-(phenyl ethynyl) picolinates as new stable and reactive glycosyl donors activated by Au [I] catalysis. This study aims to understand the reactivity differences between a simple ortho-phenylethynyl benzoate donor versus a phenyl ethynyl picolinate donor under gold (I) catalysis. The study establishes that, contrary to the general expectation, the picolinate donors are more reactive than the corresponding orthobenzoate alkyne donors, presumably due to the thermodynamic stability of the leaving group under the catalytic conditions. In addition, even with the presence of a Lewis basic nitrogen atom, the alkyne activation by gold (I) is the predominant mode of activation of the leaving group, due to the soft character of gold, leading to the cyclic product and not via the Lewis acidic coordination of gold with nitrogen and the ester oxygen. However, despite the alkynyl activation, the pyridine moiety fails to behave as a directing group via H-bonding with the incoming alcohol nucleophile. This study, however, paves the way for further exploration in this direction, leading to a simpler donor providing SN2-type alkyne activation.

Keywords

3-(Phenyl ethynyl) picolinate - H-bonding - Gold catalysis

Supplementary Material



Publication History

Received: 29 September 2025

Accepted after revision: 11 November 2025

Accepted Manuscript online:
11 November 2025

Article published online:
19 December 2025

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