ChemComm
Communication
7 For reviews on the use of [2+2] photocycloaddition reactions in
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8 (a) P. Selig and T. Bach, Angew. Chem., Int. Ed., 2008, 47, 5082–5084;
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9 (a) H. Suginome, K. Kobayashi, M. Itoh and S. Seko, J. Org. Chem.,
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Scheme 3 Synthetic sequence to (À)-pinolinone (1) from enantiomeri-
cally enriched [2+2] photocycloaddition product 3f.
12 (a) T. Bach, H. Bergmann and K. Harms, Angew. Chem., Int. Ed.,
2000, 39, 2302–2304; (b) T. Bach, H. Bergmann, B. Grosch, K. Harms
and E. Herdtweck, Synthesis, 2001, 1395–1405.
In summary, the first total synthesis of (À)-pinolinone (1)
has been accomplished via an enantioselective intermolecular
[2+2] photocycloaddition of 3-acetoxyquinolone (4) and an
appropriate silyl ketene acetal. Further key steps included a
selective ring expansion of the cyclobutane ring to a g-lactone
and the subsequent conversion of the latter compound by a
reduction/olefination sequence.
This project was supported by the Deutsche Forschungsgemeinschaft
(Ba 1372-10, GRK 1626), by the TUM Graduate School, and by the
Fonds der Chemischen Industrie. Olaf Ackermann and Marcus
Wegmann are acknowledged for help with the HPLC analyses.
¨
13 M. M. Maturi, M. Wenninger, R. Alonso, A. Bauer, A. Pothig,
E. Riedle and T. Bach, Chem.–Eur. J., 2013, 19, 7461–7472.
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15 For the use of a Lewis acid (SnCl4) in an enantioselective Baeyer–
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16 The starting material for the total synthesis was generated by
enantioselective [2+2] photocycloaddition reactions, which were
not consistently performed at À70 1C but – due to insufficient
cooling – also at slightly elevated temperatures. As known from
previous work6,12 and as detailed in the ESI† the enantioselectivity
decreases with increasing irradiation temperature.
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´
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5 For recent reviews on enantioselective photochemical reactions, see:
(a) C. Yang and Y. Inoue, Chem. Soc. Rev., 2014, 43, DOI: 10.1039/
c3cs60339c; (b) C. Mu¨ller and T. Bach, Aust. J. Chem., 2008, 61,
557–564.
6 (a) T. Bach and H. Bergmann, J. Am. Chem. Soc., 2000, 122, 20 The reported value for the specific rotation was [a]2D0 = À 9.4
11525–11526; (b) T. Bach, H. Bergmann, B. Grosch and K. Harms,
J. Am. Chem. Soc., 2002, 124, 7982–7990.
(c = 0.128, CHCl3).1 For the synthetic material the specific rotation
was determined as [a]2D0 = À6.3 (c = 0.16, CHCl3).
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Chem. Commun., 2014, 50, 3353--3355 | 3355