C O M M U N I C A T I O N S
good yields (entries 19 and 21). Additionally, use of (+)-
camphorsultam as a chiral auxiliary (1c′) allowed facile access to
the diastereomeric products 4s′ and 4t′ (entries 20 and 22).
ꢀ-lactone 6 as confirmed by 1H NMR and ESI-MS.19 In an
alternative way, reductive removal of the auxiliary of 5 by treatment
with lithium aluminum hydride was also feasible, giving the diol 8
as a single stereoisomer in 70% yield.
In summary, we successfully renovated the classical Roskamp
reaction to the unprecedented asymmetric redox C-C bond forming
reaction. The key feature of our finding is the attachment of the
camphorsultam as an auxiliary of the diazocarbonyl compounds
which is critically important to not only impart its chirality but
also determine the fate of the transient diazonium intermediate
leading to the desired compounds chemoselectively.
Table 1. Asymmetric Redox C-C Bond Formationa
Acknowledgment. This work was partially supported by a
Grant-in-Aid for Scientific Research from MEXT, Japan. T.H.
thanks a Grant-in-Aid for Young Scientists (B). Y.N. thanks the
Research Fellowships of JSPS for Young Scientists.
Supporting Information Available: Experimental details and
characterization data for new compounds. This material is available
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a Conditions: (a) TiCl4, H2CdCHCH2SnBu3, CH2Cl2, -20 °C, 94%; (b)
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