Journal of the American Chemical Society
COMMUNICATION
moieties has also been demonstrated. Further mechanistic studies
are currently underway and will be reported in due course.
’ ASSOCIATED CONTENT
S
Supporting Information. Experimental procedures and
b
compound characterization data. This material is available free of
’ AUTHOR INFORMATION
Figure 3. Proposed mechanism.
Corresponding Author
Competition studies revealed that 1,1-disubstituted olefins
react more quickly than the analogous terminal olefins, consis-
tent with an electrophilic radical addition to the olefin.27 In addi-
tion, evidence supporting a carbocation intermediate was found
during early optimization experiments utilizing 4-penten-1-ol,
which resulted in the isolation of 828 in 10% yield. Resubjection
of 3d to the reaction conditions or refluxing toluene did not
result in the formation of the tetrahydrofuran 8 (eq 1). There-
fore, we conclude that 8 is formed by competitive trapping of a
carbocation during the course of the ATRA reaction. However,
when external nucleophiles, including water and LiCl (in place of
LiBr), were added in an attempt to quench the carbocation, only
the bromohydrin was observed in all cases.27,29
’ ACKNOWLEDGMENT
Financial support from start-up funds from Boston University
and partial support from the NIGMS (P50-GM067041) is grate-
fully acknowledged. NMR (CHE-0619339) and MS (CHE-
0443618) facilities at BU are supported by the NSF. We thank
Dr. Jagan Narayanam for helpful suggestions. J.D.N. and M.D.K.
thank Boston University for Graduate Fellowships. J.W.T. thanks
Vertex for a Graduate Fellowship.
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In conclusion, we have developed a simple protocol for ATRA
to olefins using the photoredox catalyst [Ir(dF(CF3)ppy)2-
(dtbbpy)]PF6, which is capable of coupling a wide variety of
halogenated compounds to terminal olefins and disubstituted
olefins under mild conditions to give excellent yields. Conversion
of the products to a variety of synthetically and biologically useful
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dx.doi.org/10.1021/ja108560e |J. Am. Chem. Soc. 2011, 133, 4160–4163