C O M M U N I C A T I O N S
Table 2. Selective Oxygenation of Various Hydrocarbonsa
idenemethyl-PINO was selectively obtained in good yield (entry
19). Similarly, allylbenzene was oxygenated to afford the isomerized
cinnamyl-PINO adduct (entry 21).
The obtained PINO adducts could be readily converted to the
corresponding alcohols or hydroxylamine species (Scheme 2),17
thus demonstrating the synthetic utility of the oxygenated products.
Scheme 2
In summary, we have developed a convenient protocol for the
C-H functionalization of hydrocarbons. A broad range of substrates
are selectively oxygenated at the benzyl or allylic position using
stoichiometric amounts of N-hydroxyphthalimide and PhI(OAc)2
in the presence of CuCl catalyst, thus offering a new possibility of
the selective C-O bond-forming methodology.
Acknowledgment. This research was supported by the Korea
Research Foundation Grant (KRF-2006-312-C00587) and the
EEWS program at KAIST.
Supporting Information Available: The experimental procedures,
analytical data, and copies of NMR spectra of products. This material
References
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a Substrate (10 equiv), NHPI (1.0 equiv), PhI(OAc)2 (1.0 equiv), and
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(5) See the Supporting Information for details.
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Oxone, and 1,4-benzoquinone. See the Supporting Information for details.
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of substituents on ethylbenzene derivatives displayed little effects
on the reaction efficiency (entries 1-5). Reactivity of 2-ethylpy-
ridine was also similar to that of ethylbenzene (entry 6). Interest-
ingly, a substrate bearing a radical-sensitive moiety was also
efficiently oxygenated without rearrangement (entry 7), implying
that recombination of two resultant radical species, PINO and
cyclopropylcarbinyl in this case, is much faster than the ring-
opening process of the later radical.14
Reactions of bi- or tricyclic hydrocarbons also showed an excellent
selectivity at the benzylic position (entries 9-11). Interestingly, among
two available benzylic sites in dibenzosuberane and isochroman, the
1-position was exclusively oxygenated (entries 12 and 13), and its
structure of the former product was determined by an X-ray crystal-
lographic analysis.5 Toluene was smoothly reacted with NHPI to afford
the benzyl-PINO adduct (entry 14), whereas reaction of p-xylene gave
lower yield (entry 15).15 The observation that both 1-methylnaphthalene
and 8-methylquinoline displayed similar efficiency implies that the
plausible chelation effect is not appreciable in the present system
(entries 16 and 17).16 Tetrahydrofuran was selectively converted to
its R-PINO adduct in good yield (entry 18).
It was intriguing to observe that alkenes reacted with NHPI to
allow for the introduction of the PINO group at the allylic position
with the concurrent isomerization of double bond. For instance,
when vinylcyclohexane was employed as a substrate, cyclohexyl-
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