Organic Letters
Letter
ACKNOWLEDGMENTS
We thank NSF (CHE 1404063) and ACS PRF (51827-ND7)
for financial support.
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REFERENCES
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(21) Irradiation with a 450 W medium pressure mercury lamp with a
Pyrex filter sleeve in a Honovia photoreaction box without deaeration.
1
The yield was determined by H NMR spectroscopy analysis unless
indicated otherwise.
(22) A complex mixture was obtained when the same reaction was
carried out in DMF, MeCN, THF, diethyl ether, or acetone. The
reaction of 7 in pure 1-butylamine led to <10% conversion. In
methanol, the reaction of 3a with amine showed similar reactivity.
(23) Wang, Y.-H.; Wan. P. Unpublished results.
(24) With 1.2 equiv of acetic acid, the conversion of 10b in the
photoreaction was only 40%.
(25) Without using HCl, irradiation of 10 (5 mM in CD3OD) with
0.5% of CHCl3 (v/v) for 10 min also resulted in effective cleavage of
the C−N bond. Presumably, HCl was generated in situ from methanol
and chloroform upon irradiation. We examined several acid-promoted
reactions by using light-generated acid from CHCl3/MeOH. For
example, irradiation of 3,4-dihydro-2H-pyran (DHP) in methanol
showed no sign of reaction; however, in the presence of chloroform,
under the same irradiation conditions, DHP was converted to the
corresponding THP-OMe. If irradiation was stopped before complete
conversion of DHP and the reaction mixture was kept in the dark, the
remaining DHP slowly converted to the THP-OMe product.
Irradiation of CHCl3/MeOH first and then mixing with DHP in the
dark also led to clean production of THP-OMe. In another example,
the light-generated acid removed MMTr to release alcohol in excellent
yields.
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dx.doi.org/10.1021/ol503473c | Org. Lett. 2015, 17, 170−172