Tandem Michael addition–carbene insertion reaction of 1-alkynyl(aryl)(tetrafluoroborato)-λ³-bromanes: 1-(phenylsulfonyl)- and 1-(trifluoromethylsulfonyl)cyclopentene annulation

Abstract

Exposure of 1-alkynyl[p-(trifluoromethyl)phenyl](tetrafluoroborato)-lambda(3)-bromanes to sodium benzenesulfinate or sodium trifluoromethanesulfinate in dichloromethane at 0 degree C under argon resulted in tandem Michael-carbene insertion reactions to produce 1-sulfonylcyclopentenes selectively, with concomitant formation of a small amount of rearranged 1-alkynyl sulfones.

Recent advances in alkylidene carbene chemistry

“…99 Like the hypervalent iodine reagents described above, alkynylbromonium reagents undergo reaction with sulfinate nucleophiles to give the corresponding cyclopentenes. 100 However, Ochiai demonstrated less reactive nucleophiles such as tosylates and mesylates react to give alkynes 123aed and cyclopentenes 124a,b (Scheme 63). 99 Reaction with weak nucleophiles such as sulfonate anions, shows that these reagents are considerably more reactive than the corresponding iodonium reagents.…”

Preparation of Alkyl Alkynyl Sulfones and Cyclic Vinyl Sulfones from Alkynyl(aryl)iodonium Salts

“…When isopropyl sulfinate was used insertion in to the primary C-H bond to form 6d was observed. Formation of cycle 6e from sulfinate 4e must proceed through insertion in to a tertiary C-H bond and this process was indeed favorable compared to rearrangement to 5e, however the 5/6 ratio was not superior to the results with insertion in to secondary C-H bonds (table 1, entries [13][14][15].…”

“…12 Ochiai has also demonstrated similar reactivity with related alkynyl(aryl)bromonium salts. 13 Recently, we demonstrated that alkynyl(aryl)iodonium tosylates salts derived from 2-iodoanisole are more stable than tosylate salts derived from other aryl groups and generally lead to higher yields of products in alkynylation and C(sp 3 )-H carbene insertion reactions. 14 We were interested in applying this methodology to a new synthetic route to alkyl and cyclic sulfones due to the dearth of preparative methods and the potential value of these compounds.…”

“…1 H NMR and 13 C NMR spectra were recorded in ppm from tetramethylsilane with the solvent resonance as the internal standard. Mass spectrometry (m/z) was performed in ESI mode (qTOF), with only molecular ions being reported.…”

Hypervalente Bromverbindungen: kleine Analoga von hypervalenten Iodverbindungen oder “Enfants Terribles”?

“…Nach der Addition von Sulfinat an die Dreifachbindung und der Bildung des Carbenintermediats 14 wird die Reaktion durch eine C-H-Insertion unter Bildung von 15 beendet. [10] Mit 2-Thiobenzimidazol (16) als Nucleophil können tricyclische Azapentalene 17 in guten Ausbeuten erhalten werden (Schema 6, unten). [11] Vinylbromane wurden erstmals durch Umsetzung von Vinylbromid mit einem Fluormethan-Antimonpentafluorid-Komplex synthetisiert.…”