Abstract
A mixture of phenylmercuric acetate and trifluoromethanesulfonic
acid or silica gel supported phenylmercuric trifluoromethanesulfonate
(silaphenyl mercuric triflate) efficiently catalyzed the formation
of pyrroles from homopropargyl azide derivatives. The reactions
proceed using 20 mol% of the heterogeneous catalyst with
yields of isolated pyrroles ranging from 74% to 99%.
Key words
cyclization - heterocycles - heterogeneous
catalysis - azides - alkynes
References and Notes
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Preparation of
Silaphenylmercuric Triflate (10) and a Typical Experimental Procedure
for a Silaphenyl-mercuric Triflate Catalyzed Cyclization
To
a suspension of dried silaphenylmercuric acetate 9 (0.2 mmol/g,
500 mg, 0.1 mmol) in MeNO2 (5 mL) was added TfOH (17.4 µL,
0.2 mmol), and the mixture was stirred for 10 min at r.t. The filtered
residue was washed with MeNO2 (10 mL) and dried to give
silaphenylmercuric triflate 10. Next, MeNO2 (4
mL) and prepared 10 were added to a dried two-neck
flask. To the stirred suspension of 10 was
added a solution of 1 (86 mg, 0.5 mmol)
in MeNO2 (1 mL) at r.t. under argon. The mixture was
stirred at r.t. for 5 min, and the catalyst was then removed by
filtration and washed with MeNO2 (10 mL). The combined
filtrates were concentrated under reduced pressure. Purification
by column chromatog-raphy on silica gel using hexane and EtOAc (10:1)
gave pyrrole 2 (70 mg, 97%).
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In all cases (Table
[³]
), recovery of 10 was between 99.29% and 99.89%.
