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http://www.sigmaaldrich.com/etc/medialib/docs/Aldrich/Acta/al_acta_30_01.pdf Aldrichimica Acta Volume 30 No 4 (pdf) from http://www.sigmaaldrich.com/chemistry/chemical-synthesis/learning-center/aldrichimica-acta.html Sigma-Aldrich

Decomposition of 4 in the presence of cis-piperylene at room temperature results in the stereocontrolled formation of trans-cycloheptadiene 27 in 90% ee (96% ee at −78 °C).