A method for the synthesis of 3-methylene-1,4-cycloheptadiene
derivatives
via an 8π electrocyclization reaction was developed. The triene
substrate bearing a phosphate or carbamate group was prepared from
γ,δ-unsaturated esters and α,β-unsaturated
aldehydes in four steps. Upon treatment with NaHMDS or KHMDS, the
substrate formed a heptatrienyl anion, which underwent electrocyclization
and subsequent β-elimination of the leaving group. The product
could be converted into a tropylium salt in two steps.
Other bioactive products U 1300 Convergent Synthesis of the IJKLM-Ring Part of Ciguatoxin CTX3C. -(DOMON, D.; FUJIWARA*, K.; MURAI, A.; KAWAI, H.; SUZUKI, T.; Tetrahedron Lett. 46 (2005) 48, 8285-8288; Div. Chem., Grad. Sch. Sci., Hokkaido Univ., Sapporo 060, Japan; Eng.) -Mais 05-221
A new variant of fused cyclic ether synthesis based on Ireland-Claisen rearrangement and ring-closing olefin metathesis (RCM) was developed. The Ireland-Claisen rearrangement of a (Z)-3-alkoxyprop-2-en-1-yl glycolate ester having a cyclic ether on the oxygen at C3 of the (Z)-prop-2-en-1-yl group stereoselectively produced an anti-,-dialkoxyester, which was successfully transformed to a fused bicyclic ether via a reaction sequence including RCM.
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