Page 904 - Advanced Organic Chemistry Part B - Reactions & Synthesis

880 Scheme 10.2. (Continued)

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was used in syntheses of derivatives of robustadial, which are natural products from
Eucalyptus that have antimalarial activity.
Entries 8 to 15 are examples of intramolecular reactions. Entry 8 involves two
unactivated double bonds and was carried out at a temperature of 280 C. The product

was a mixture of epimers at the ester site but the methyl group and cyclohexenyl
double bond are cis, which indicates that the reaction occurred entirely through an
endo TS.
CO C H CO C H
2 2 5
2 2 5

H
CH 3
The reaction in Entry 9 was completely stereospecific. The corresponding E-isomer
gave mainly the cis isomer. These results are consistent with a cyclic TS for the
hydrogen transfer.
O
CF 3 N H CH 3 E E
H
E
E
E CO C H H E Z
2 2 5
The stereoselectivity of the reaction in Entry 10 is also consistent with a TS in which
the hydrogen is transferred through a chairlike TS.
H H
CH 3
CH 3 CO 2 C 2 H 5 CH 3 CO 2 C 2 H 5
CO 2 C 2 H 5
H
CH 3
CH 2
TBDPSO CO 2 C 2 H 5
H TBDPSO TBDPSO CO 2 C 2 H 5
H CO 2 C 2 H 5 H
Entry 11 illustrates the facility of a Sc(OTf) -mediated reaction. The
3
catalyst in Entry 12 is a hindered bis-phenoxyaluminum compound. The proton removal