Journal of the American Chemical Society
COMMUNICATION
this rearrangement would be to reduce steric hindrance around
the Me3SiO-substituted quaternary carbon of 5.
Carriꢀe, R.; Jazouli, Md. Tetrahedron Lett. 1997, 38, 6665–6668.
(b) Matteson, D. S. In Science of Synthesis: Houben-Weyl Methods of
Molecular Transformations; Kaufmann, D. E., Matteson, D. S., Eds.;
Georg Thieme Verlag: Stuttgart, 2005; Category 1, Vol. 6, pp 607-622.
For preparation of R-oxygenated organoboron compounds, see:
(c) Molander, G. A.; Ham, J. Org. Lett. 2006, 8, 2031–2034. (d)
Molander, G. A.; Canturk, B. Org. Lett. 2008, 10, 2135–2138. (e)
Shimizu, M.; Fujimoto, T.; Liu, X.; Minezaki, H.; Hata, T.; Hiyama, T.
Tetrahedron 2003, 59, 9811–9823. (f) Shimizu, M.; Fujimoto, T.; Liu,
X.; Hiyama, T. Chem. Lett. 2004, 33, 438–439. (g) Shimizu, M.;
Fujimoto, T.; Liu, X.; Takeda, Y.; Hiyama, T. Heterocycles 2008,
76, 329–351.
In summary, we developed photochemically promoted acyl-
aryl, acyl-alkenyl, and acyl-alkyl cross-coupling reactions of
acylsilanes with organoboronic esters to afford a wide range of
ketones under mild reaction conditions. This is a quite rare exam-
ple that photochemistry of acylsilanes is efficiently applied for
carbon-carbon bond-forming reactions. It is noteworthy that
this overall transformation can be achieved without the use of
transition metal catalysts.23,24
(10) The X-ray analysis of a stable crystalline derivative 8 obtained
from 4-bromobenzoyltrimethylsilane and 4-bromophenylboronic acid
pinacol ester under the optimum conditions also supported the structure
of 7aa. See SI for details.
’ ASSOCIATED CONTENT
S
Supporting Information. Experimental procedures and
b
spectral data for the new compounds, NMR data in Scheme 3,
and crystallographic data for 8 mentioned in ref 10. This material
(11) Related rearrangement reactions: (a) Hesse, G.; Haag, A.
Tetrahedron Lett. 1965, 1123–1125. (b) Seyferth, D.; Prokai, B. J. Am.
Chem. Soc. 1966, 88, 1834–1835. (c) See also: Suzuki, A; Nozawa, S.;
Miyaura, N.; Itoh, M.; Brown, H. C. Tetrahedron Lett. 1969, 2955–2958.
(12) The photoirradiation was carried out through the super-cold
filter (Asahi Optics SC0751) so as not to raise the temperature of the
reaction mixture. Since 4-MeOC6H4CHO, probably due to moisture in
the reaction mixture, was observed in the crude mixture, examinations in
Tables 1 and 2 were performed in the presence of MS4A. See: Wegert,
A.; Behr, J.-B.; Hoffmann, N.; Miethchen, R.; Portella, C.; Plantier-
Royon, R. Synthesis 2006, 2343–2348. See also ref 3b.
’ AUTHOR INFORMATION
Corresponding Author
’ ACKNOWLEDGMENT
(13) The reaction of 1a and 3a under thermal conditions (micro-
wave, 180 °C in o-dichlorobenzene or microwave, 250 °C in decalin)
resulted in a complex mixture, and neither 7aa nor 6aa could be
detected. See ref 3c.
This research was partly supported by the Sumitomo Founda-
tion and a Grant-in-Aid for Scientific Research from the Ministry
of Education, Culture, Sports, Science, and Technology of Japan.
(14) All the reactions were carried out by using degassed solvents.
The yields in parentheses are the combined yield of 7aa and 6aa deter-
mined by H NMR because a small amount of the ketone 6aa was
’ REFERENCES
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(15) Direct purification of the crude mixture by preparative TLC
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(8) Photoirradiation was carried out through band-pass filter (λ =
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(20) Saturated ketone 60ia is assumed to be formed by protonation at
the γ-position of the allylboronic ester moiety of the primary product 7ia.
(21) In all reactions employing an aroylsilane and/or an arylbor-
onate (Table 2, entries 1-18), 1H NMR spectra of the crude materials
suggested exclusive formation of the rearranged product 7.
(22) Theoretical calculations (RB3LYP/6-31G(d)//RHF/6-31G)
of 5 and 7 bearing phenyl-phenyl, phenyl-methyl, and ethyl-methyl
substituents suggested that the rearranged product 7 is thermodynamically
more stable than 5 regardless of the substituents on the quaternary carbon.
(23) Transition metal-catalyzed cross-coupling reactions of acylsi-
lanes and stannanes and silylcarbonylation reactions of acylsilanes:
3718
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