Base-Catalyzed Cascade 1,3-H Shift/Cyclization Reaction to Construct Polyaromatic Furans
Scheme 5. A possible mechanism for the base-catalyzed cascade 1,3-H shift/cyclization reaction of diynyl diesters to provide
polyaromatic furans.
lectivity. Formation of the dialkenyl diketone F was Acknowledgements
unlikely because no regioisomer was obtained in the
reaction of compound 5.
In conclusion, we have developed a new method to
construct a series of the unfused polyaromatic furan
Support of this work by the grants from National Sciences
Foundation of China (Nos. 20872176 and 21072224) is grate-
fully acknowledged.
derivatives from the base-induced reaction of the
diynyl-1,6-diols through a novel cascade 1,3-H shift/
References
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vealed that a 1,3-H shift was the rate-determining
step, which primarily proceeded through a contact ion
pair process. This is the first report, to the best of our
knowledge, of a tandem process by using the base-cat-
alyzed 1,3-H shift as the starting step.
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Experimental Section
Typical Procedure for the DBU-Mediated Reaction
of Diynyl Diesters
To an oven-dried Schlenk tube containing a magnetic stir
bar, 0.2 mmol substrate 1a was added under N2, followed by
20 mol% DBU and 2 mL THF. The resulting mixture was al-
lowed to stand at 608C, until complete consumption of the
starting material was shown TLC monitoring. The reaction
was quenched by addition of 2 mL saturated aqueous am-
monium chloride solution, extracted with ethyl acetate, and
the combined organic layers were then washed with brine,
dried over anhydrous sodium sulfate and filtered. After re-
moving the solvent, the residue was purified by column
chromatography on silica gel to afford product 2a; yield:
83%.
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