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Synlett 2024; 35(14): 1719-1724
DOI: 10.1055/a-2236-0974
letter

Synthesis of Triarylpyrylium Salts Using a Mild, Eco-friendly Route

Connor Owen‡
a   Department of Chemistry, Mount St. Mary’s University, Emmitsburg, MD 21727, USA
,
Casey Spiridopoulos‡
a   Department of Chemistry, Mount St. Mary’s University, Emmitsburg, MD 21727, USA
,
Nicholas Starvaggi 
a   Department of Chemistry, Mount St. Mary’s University, Emmitsburg, MD 21727, USA
,
Zachary Morrow
b   Department of Chemistry, West Chester University, West Chester, PA 19383, USA
,
Danielle Chirdon∗
b   Department of Chemistry, West Chester University, West Chester, PA 19383, USA
,
Isaac Mills∗
a   Department of Chemistry, Mount St. Mary’s University, Emmitsburg, MD 21727, USA
› Author AffiliationsThe authors would like to acknowledge the National Science Foundation Major Research Instrumentation Program (NSF MRI, grant 0619209) for funding of the 400 MHz NMR instrumentation.
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Abstract

Pyrylium salts based on a cationic oxygen heterocycle are a key class of chromophores. However, synthesis of these salts generally requires use of harsh acids, copious organic solvents, and in many cases, hazardous conditions. This work provides a two-pot synthesis for substituted triphenyl pyrylium salts wherein chalcone intermediates are first prepared and then mild methanesulfonic acid is used in combination with a dehydrating agent to drive pyrylium cyclization. Purification is achieved through a simple, aqueous workup involving counterion metathesis which avoids the need for environmentally unfriendly organic solvents. This mild, green approach has been applied to synthesize a collection of known pyryliums as well as a new family of red-shifted pyrylium chromophores bearing p-pyrrolidinylphenyl substituents. The synthesis of the latter group demonstrates that unlike other current methods, our approach offers enhanced functional group tolerance as well as finer control over substituent placement.

Key words

photochemistry - green chemistry - condensation - chromophores - cyclization

Supporting Information

    Supporting information for this article is available online at https://doi.org/10.1055/a-2236-0974.
  • Supporting Information


Publication History

Received: 20 October 2023

Accepted after revision: 28 December 2023

Accepted Manuscript online:
28 December 2023

Article published online:
29 January 2024

© 2023. Thieme. All rights reserved

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