5‐(Alkynyl)dibenzothiophenium Triflates: Sulfur‐Based Reagents for Electrophilic Alkynylation

Abstract

The synthesis of a series of 5‐(alkynyl) dibenzothiophenium triflates, prepared from dibenzo[b,d]thiophene 5‐oxide and the corresponding trimethylsilyl‐substituted alkynes is reported. Their structures were determined by X‐ray crystallography, and their reactivities as electrophilic alkynylation reagents evaluated. Their broad substrate scope and functional‐group tolerance illustrate their potential to become an alternative to the broadly used EBX reagents. Isotope labeling studies reveal that alkynyldibenzothiophenium salts may undergo attack by nucleophiles at either the α‐ or β‐carbon atom depending on the nature of their substitution pattern. Subsequent elimination of the dibenzothiophene unit and 1,2‐migration of one of the groups (in case of β‐attack) affords the desired alkynes.

Microwave-Assisted Copper-Catalyzed Coupling of Bromoalkynes and Sulfonamides: Rapid Synthesis of N-Sulfonyl Ynamides

“…The most common method for accessing ynamides is N-alkynylation of sulfonamides with various alkynes, such as bromoalkynes, 9 iodoalkynes, 10 chloroalkynes, 11 terminal alkynes, 12 or alkynyl carboxylic acids, 13 in the presence of a Cu or Fe catalyst (Scheme 1a ). Furthermore, preactivated alkynes, such as copper acetylides, 14 alkynyl borates, 15 alkynyl bismuths, 16 alkynyl sulfonium salts, 17 alkynyl iodonium salts, 4a 18 and alkynyl benziodoxolones, 19 have been developed for the synthesis of ynamides (Scheme 1b ). Notably, haloalkenes, such as 1,2-dibromo, 1,2-dichloro, and 1,1-dichloro alkenes can be used as precursors for haloalkynes (Scheme 1c ).…”