A one pot alkenylation followed by a stereoselective
Alder-ene
cycloisomerization of cyclopropenes give (aza)spiro[2.4]heptanes and
spiro[2.5]octanes in high yields. Total trans diastereoselectivity
is achieved for spiro[2.4]heptanes if the cyclopropene is monosubstituted
in C3. When an α,β-unsaturatedcarbonyl-containing bromide
is used, an alternative cyclization takes place giving cyclopenta[c]cyclopropa[b]pyrans.
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