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. Author manuscript; available in PMC: 2010 Aug 20.
Published in final edited form as: Org Lett. 2009 Aug 20;11(16):3682–3685. doi: 10.1021/ol901523g

Table 2.

One-Pot Synthesis of 6,8-Dioxabicyclo[3.2.1]oct-3-en-2-ones[a]

graphic file with name nihms-134654-f0004.jpg
entry reactant R R1 % yield % ee
1 (−)-syn-3 H Me 80, 8 98.7[b]
2 (±)-syn-5 H E-prop-1-enyl 56, 9 -
3 (±)-syn-6 H phenyl 56, 10 -
4 (±)-syn-7 Me Et 73, 11 -
5 (−)-anti-3 H Me 70, 12 98.7[b]
6 (±)-anti-5 H E-prop-1-enyl 44, 13 -
7 (±)-anti-6 H phenyl 61,[c] 14 -
8 (±)-anti-7 Me Et 66, 15 -
[a]

NOPF6 and NOBF4 were equally effective.

[b]

Starting from 98.7% ee (−)-syn-3 and (−)-anti-3.

[c]

Epimerization was observed at C7 (exo:endo 3:10) which is likely the result of a retro-aldol reaction of anti-6.