First intramolecular trapping and structural proof of the key intermediate in the formation of indolizine photochromicsElectronic supplementary information (ESI) available: Figs. S1 and S2. See http://www.rsc.org/suppdata/cc/b1/b101044l/

Abstract

The reaction of substituted spirocyclopropenes 1 with 1-(3,5-dinitrophenyl)-3,4-dihydroisoquinoline 2 in dry ether solution afforded not only the expected THI 4 by 1,5-electrocyclization but also novel fluorenespiroazanorcaradienes 5 which is the first intramolecularly trapped product of the key intermediate in the formation of indolizine photochromics.