and
complete
regioselectivity.
Additionally,
cyclic
We appreciate financial support from the Fundamental and
Advanced Research Projects of Chongqing City (No.
cstc2018jcyjA0150), and Chongqing Science and Technology
Commission (cstc2015zdcy-ztzx120003).
aryloxyketones with a bromo group were also suitable substrates.
Notably, the cyclodehydration of these unsymmetrical cyclic
aryloxyketones occurred preferentially at the 1- or 2-position of
the naphthyl moiety, producing the corresponding single isomers.
References and notes
Table 3. Condensation reaction of acyclic aryloxyketones.a, b
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a
Reagents and conditions: 1 (0.5 mmol), TiCl4 (0.5 mmol), CH2Cl2 (1 mL),
r.t. b Isolated yield. c 40 oC.
To further demonstrate the utility of this method, several
aryloxyketones prepared from acyclic haloketones and phenols
were examined. The reactions of aryloxybutanones (Table 3, 4a-e)
proceeded to completion in 1 h at room temperature to give the
corresponding benzofurans or naphthofurans with excellent
yields. In contrast, the reactions of aryloxypentanones (Table 3,
4f-g) were slower, especially phenoxypentanone (4f) which
required heating. Moreover, the use of aryloxyketones derived
from 1-halo-2-ketones (Table 3, 4h-k) gave naphthofurans in
good to excellent yields. However, the reactions were more
sluggish, and longer reaction times and heating were necessary.
Remarkably, all unsymmetrical aryloxyketones afforded a single
isomer.
In summary, we have developed an efficient method for the
synthesis of a diverse range of benzofurans and naphthofurans
via the intramolecular cyclodehydration of aryoxyketones using
titanium tetrachloride as the dehydrating agent. Cyclic and
acyclic aryloxyketones were readily condensed to give the
corresponding benzofurans and naphthofurans in good to
excellent yields with high regioselectivity.
Supplementary Material
Supplementary material that may be helpful in the review
process should be prepared and provided as a separate electronic
file. That file can then be transformed into PDF format and
submitted along with the manuscript and graphic files to the
appropriate editorial office.
Acknowledgments