What is it about?
Alkynyl organometallic reagents are valuable tools for constructing carbon–carbon bonds, but they are typically prepared from terminal alkynes using strong bases. In this study, we developed a new method for generating alkynylmagnesium chlorides from readily available 1-chlorovinyl p-tolyl sulfoxides. The transformation proceeds through a sequence of sulfoxide/magnesium exchange, Fritsch–Buttenberg–Wiechell (FBW) rearrangement of magnesium alkylidene carbenoids, and deprotonation of the resulting terminal alkynes by a turbo Grignard reagent. The alkynylmagnesium chlorides generated in situ react efficiently with a variety of electrophiles, including aldehydes, ketones, isocyanates, esters, epoxides, and halides, providing a wide range of functionalized alkynes.
Featured Image
Photo by Alex on Unsplash
Why is it important?
Alkynylmagnesium chlorides are versatile intermediates for organic synthesis, but their preparation often requires handling terminal alkynes, some of which are volatile. This work demonstrates that stable and readily prepared 1-chlorovinyl p-tolyl sulfoxides can serve as practical alkynylmagnesium chloride precursors. The method provides access not only to common alkynyl Grignard reagents but also to species corresponding to low-boiling alkynes such as propyne and 1-butyne, as well as ethynylmagnesium chloride. In addition, the approach offers advantages in functional-group tolerance compared with conventional methods such as the Corey–Fuchs protocol. More broadly, the study expands the synthetic utility of magnesium alkylidene carbenoids and highlights their value as intermediates for alkyne synthesis.
Perspectives
This study originated from our continuing interest in magnesium alkylidene carbenoids generated from 1-chlorovinyl p-tolyl sulfoxides. While these intermediates were known to undergo FBW rearrangements to give alkynes, we wondered whether the process could be extended further to generate useful alkynyl organometallic reagents in situ. It was particularly satisfying to find that a simple sequence of exchange, rearrangement, and deprotonation reactions could provide alkynylmagnesium chlorides that react with a broad range of electrophiles. I am especially pleased that the method enables access to reagents corresponding to highly volatile alkynes that are otherwise difficult to handle. I hope this work encourages the broader use of sulfoxide-based carbenoid chemistry as a practical platform for synthetic methodology development.
Associate Professor Tsutomu Kimura
Read the Original
This page is a summary of: Use of 1-chlorovinyl p-tolyl sulfoxides as alkynylmagnesium chloride sources, Tetrahedron, June 2023, Elsevier,
DOI: 10.1016/j.tet.2023.133439.
You can read the full text:
Contributors
The following have contributed to this page
